Symposium OrganizersChristopher J. Bettinger, Carnegie Mellon University
John Rogers, University of Illinois
Miha Irimia-Vladu, Johannes Kepler University
Luisa Torsi, Universita di Bari 'Aldo Moro'
Symposium Support National Science Foundation
UU2: Bio-Organic Devices for Sensing and Actuation II
Tuesday PM, April 10, 2012
Marriott, Yerba Buena, Salon 6
2:30 AM - UU2.1
Label-free Detection of Dopamine by Means of Organic Electrochemical Transistor (OECT)
Stefano Casalini 1 Francesca Leonardi 1 Fabio Biscarini 1
1Institute of Nanostructured Materials (ISMN) Bologna ItalyShow Abstract
Dopamine (DA) is a catecholamine neurotransmitter and in the central nervous system the loss of dopaminergic neurons (substantia nigra) is directly related to the Parkinson (PD) symptoms such as tremor, postural instability, slowness of movement. Nowadays, monitoring the development of the Parkinson disease in patients is performed by neuro-imaging techniques, that feature some drawbacks like i) the use of tracers and ionizing radiation, ii) the inability to provide a reliable diagnosis in the early stage of the disease and iii) the requirement of expensive facilities. For these reasons, the scientific community started to screen alternative approaches for DA sensing, such as liquid chromatography, capillary electrophoresis, electrochemical methods, complementary metal oxide semiconductor etc., in order to achieve low-cost and easier diagnostic techniques. Polysilicon nanowire field-effect transistor, ion-sensitive field-effect transistor (ISFET) and amperometric devices have been successfully fabricated for DA sensing and Tang et al. recently demonstrated the high sensitivity of organic electrochemical transistors (OECTs) towards DA electro-oxidation. Here, we propose a new sensing approach, which relies on the excellent features of the OECT for sensing purposes. Our device is composed by three polycrystalline Au electrodes, a phosphate buffer as electrolytic solution and poly(3-hexylthiophene) as semiconductor material. The gate electrode has been functionalized by self-assembly monolayer of cysteamine and 4-formylphenylboronic acid. The well-known affinity between boronic acid and the hydroxyl groups of dopamine is the key aspect of this molecular recognition. Our OECT does not exploit any faradic current, but the dramatic change of the capacitive current (i.e. leakage current), which allows a fine detection of dopamine docked onto the gate electrode. This device is able to monitor DA concentrations useful for diagnostic purposes.
2:45 AM - UU2.2
A New Class of Photovoltaic Devices with Ionically Conductive Hydrogel Matrix
Hyung-Jun Koo 1 Suk Tai Chang 2 Orlin D Velev 1
1NC State University Raleigh USA2Chung-Ang University Seoul Republic of KoreaShow Abstract
We demonstrate how water-based gels can be used as the core of novel photovoltaic cells operating on the basis of ionic current in the hydrated medium. Earlier, we reported a new class of â?osoftâ? diodes with rectifying junction formed by interfacing water-based gels doped with polyelectrolytes of opposite charge [JACS, 2007, 129:10801]. The rectification ratio of such devices can be as high as 40000 when using hydrated SiO2 nanolayers as one of the gel diode components [Small, 2010, 13:1393]. The hydrogel diodes were used as a platform for developing a radically new concept of bio-inspired hydrogel solar cells [J. Mater. Chem. 2011, 21:72]. The matrix of these photovoltaic cells is made of agarose gel, containing 98% water and 2% natural polysaccharides. Two photosensitive ions, DAS- and [Ru(bpy)3]2+, were used as photoactive molecules embedded in agarose gel matrix. The provisional mechanism of the operation of the hydrogel photovoltaics suggests that the dye ions contribute cooperatively to the photocurrent generation both on the surface of the working electrode and in the bulk of the gel. We found an efficient replacement of the Pt counter electrode with inexpensive copper foil coated with carbon. The gel photovoltaic media could host biologically derived photoactive molecules, such as Chlorophyll and Photosystem II. We will discuss how such devices can form the basis of bioinspired â?oartificial leavesâ? by embedding a microvascular network of channels mimicking leaf veins inside the gel. This network could enable efficient replenishment of the photoactive reagent, which was demonstrated in a preliminary way by constructing self-regenerating water-based dye sensitized solar cells. The results point the way towards truly biomimetic energy harvesting systems.
3:00 AM - *UU2.3
Organic Electronic Devices for Neural Interfacing
George Malliaras 1
1Ecole National Superieure des Mines de St. Etienne Gardanne FranceShow Abstract
A visible trend over the past few years involves the application of organic electronic devices to the interface with biology, with applications both in sensing and in actuation. Examples include biosensors, artificial muscles, and neural interface devices. The latter are of particular interest, as organic materials offer several distinct advantages compared to incumbent technologies, including mechanical flexibility, enhanced biocompatibility, better signal-to-noise ratio and capability for drug delivery. As such, they promise to yield new tools for neuroscience and enhance our understanding on how the brain works. After a brief introduction, I will present a few examples of implantable electrode arrays which utilize conducting polymer devices. Their electrical characteristics and properties such as mechanical flexibility and biocompatibility will be discussed. The talk will close with an assessment of the signal transduction mechanism.
3:30 AM - UU2.4
Interfacial Effects in Bio-molecules Integrated into OFET Devices
Maria D Angione 1 Serafina Cotrone 1 Maria Magliulo 1 Antonia Mallardi 2 Gerardo Palazzo 1 Luisa Torsi 1
1Universita degli Studi di Bari Bari Italy2CNR-IPCF, Istituto per i Processi Chimico-Fisici Bari ItalyShow Abstract
Bio-systems interfaced to an electronic device is presently one of the most challenging research activity that has relevance not only for fundamental studies but also for the development of highly performing bio-sensors. In this presentation the full integration of bio-systems such as phospholipid bilayers or proteins into an organic field-effect transistor (OFET) structure is proposed. Strikingly, the results show that both the electronic properties and the bio-layer functionality are fully retained. The platform bench-tests involved phospholipids and bacteriorhodopsin integrating OFETs exposed to 1-5% anesthetic doses that reveal drug-induced membrane changes. This challenges the current anesthetic action model relying on the so far provided evidence that doses much higher than clinically relevant ones (2.4%) do not alter lipid bilayers structure, significantly. Furthermore, a streptavidin embedding OFET shows label-free biotin electronic detection at 10 part-per-trillion concentration level, reaching state-of-the-art fluorescent assay performances. Extensive explored control experiments show the detection is also highly specific. These examples show how the proposed bio-electronic platform, besides resulting in extremely performing biosensors, can open to gather insights into biological relevant phenomena involving interfacial modifications that can be electronically detected. References  L. Torsi, G. Palazzo, D. Angione, N. Cioffi, M. Magliulo, S. Cotrone, G. Scamarcio, L. Sabbatini, A. Mallardi;. Field-effect transistors based on multilayers of self-assembled biological systems and organic semiconductor layer: processes for their realization and use as sensors;. European Patent. EP 10425146.7.  M.D. Angione, S. Cotrone, M. Magliulo, A. Mallardi, D. Altamura, C. Giannini, N. Cioffi, L. Sabbatini, E. Fratini, P. Baglioni, G. Scamarcio, G. Palazzo and L. Torsi; Interfacial electronic effects in functional bio-layers integrated into organic field-effect transistors, submitted.
4:15 AM - UU2.5
Electroactive, Multi-component Microfibers for Skeletal Muscle Regeneration
Kristin M Fischer 1 Daniel H Flagg 2 Abby R Whittington 1 2 John H Rossmeisl 1 3 Joseph W Freeman 1 4
1Virginia Tech Blacksburg USA2Virginia Tech Blacksburg USA3Virginia-Maryland Regional College of Veterinary Medicine Blacksburg USA4Rutgers University Piscataway USAShow Abstract
Once a muscle is injured, it attempts to repair itself; however, this results in scar tissue and loss of function. Electrical stimulation has been shown to have a beneficial effect on skeletal muscle growth, differentiation, and contractile activity. We coaxially electrospun an electroactive polymer scaffold for skeletal muscle regeneration composed of poly(Îµ-caprolactone) (PCL), multi-walled carbon nanotubes (MWCNT), and a polyacrylic acid/polyvinyl alcohol (PAA/PVA) hydrogel (H). We compared the scaffold to electrospun PCL and PCL-MWCNT scaffolds and varied the PAA/PVA hydrogel ratios: 83/17, 60/40, 50/50, and 40/60. Both SEM and fluorescent imaging confirmed the inner core/outer sheath characteristic of coaxial electrospinning. Scaffold electroactivation was investigated by suspending strips in a saline bath and 10, 15, and 20V were applied. Only scaffolds containing all of the components actuated when electrically stimulated. Average angular speeds were calculated from the resulting scaffold movement (initial, secondary, and relaxation). The application of 20V to each of the scaffolds elicited the best response for all three angular speeds calculated. The 83/17 initial actuation average angular speed was significantly greater than all the other scaffolds subjected to 20 V and all responses at 10V and 15V. Although not all the scaffolds experienced a secondary actuation, the 50/50 secondary actuation average angular speed at 20V was significantly larger. No significant difference was found for any of the relaxation average angular speeds. For biological analysis, rat primary skeletal muscle cells were seeded onto the scaffolds and an MTS assay measured cellular activity. PCL-MWCNT-H scaffolds displayed a large increase in activity on day 21 and PCL scaffolds on day 28. The PCL-MWCNT scaffolds remained constant throughout the study. In comparison, the varied hydrogel ratio scaffolds had similar cellular activity with no significant difference between them. PCL-MWCNT-H scaffolds supported cellular activity and attachment as large multinucleated constructs with actin interaction were seen. Muscle cells were also exposed to MWCNT to determine toxicity. Day 7 showed no difference; however on day 14, the MWCNT treated cells were significantly lower than the non-treated cells. Though this trend continued, both groups of treated cells display an increase in cellular activity over the rest of the study. The 83/17 and 40/60 scaffolds were then implanted into a cavity created in the rat quadriceps muscle. Rats were ambulatory immediately upon waking and no adverse effects or infections were seen during the study. Upon harvesting, gross examination revealed that the 40/60 scaffolds had a larger surrounding fibrous area compared to the 83/17. Although the in vivo study has been completed, histological analysis will be presented. Based on this data we conclude that the PCL-MWCNT-H scaffold has potential for use as a biocompatible artificial muscle.
4:30 AM - UU2.6
Complementary Polysaccharide Bioprotonic Field Effect Transistors
Marco Rolandi 1
1University of Washington Seattle USAShow Abstract
The quest for smaller and faster computing has focused on controlling the flow of electrons and holes in nanoscale molecular structures. In living systems, protonic and ionic currents are the basis for information processing. As such, artificial devices that can control protonic and ionic currents offer an exciting opportunity for implantable bionanoelectronics. We have recently demonstrated a biopolymer protonic field effect transistor (H+-FET). The H+-FET is made of maleic-chitosan nanofibers with hydrogen bonded water networks as ion channel mimics. Protons move along these networks following the Grotthus mechanism with a mobility of Î¼H+ â?^ 4.9 x 10-3 cm2 V-1 s-1. The acid groups in the maleic chitosan â?oproton dopeâ? the polysaccharide as a H+ type proton semiconductor. Here, I will present results from chitosan derivatives with base groups that accept protons and create â?oproton holesâ? in the polysaccharide to make a OH-- type proton semiconductor. H+-type and OH-- type devices are assembled to create complimentary bioprotonic circuitry in analogy to complimentary electronics.
4:45 AM - UU2.7
Soft-Matter Memristors and Diodes Based on Biocompatible Hydrogels and Micromoldable Liquid Metals
Ju-Hee So 1 Hyung-Jun Koo 1 Orlin Velev 1 Michael Dickey 1
1NC State University Raleigh USAShow Abstract
New types of electronic devices and circuits based on soft materials have potential applications in biomimetic circuits, green technologies, and electronic interfaces with biomaterials. We describe a new class of diodes and memory elements (memristors) composed entirely of soft materials formed by combining a moldable liquid metal and hydrogel doped with polyelectrolytes (Adv. Mat., 2011, 23:3559). The electronic functionality of these devices originates from the ability to control the electronic and ionic transport at the interface between the metal and the hydrogel (Adv. Fun. Mat., In Press). The biocompatible hydrogels, which are composed of more than 90% water, are soft, low-cost, and easy to fabricate and may be ideal for interfacing with biological molecules, cells, and tissue. The metal, which is a eutectic alloy of gallium and indium, is a low viscosity liquid with metallic conductivity at room temperature. Its surface is coated with a thin, native skin of gallium oxide. We fabricated soft and quasi-liquid electronic devices that mimic solid-state, semiconductor devices such as diodes and memristors, by sandwiching hydrogel films between molded metal electrodes. The resistance through the film stack depends on the thickness of the oxide skin, which can be controlled using pH and/or electrical bias to oxidize or reduce the skin. We will discuss the rectification characteristics of diodes as a function of the environment in the hydrogel and the on/off switching behavior of memristors composed entirely of soft organic materials.
5:00 AM - UU2.8
Spiropyran-terthiophene Polymers as Multi-Stimuli-Responsive Platforms for Biochemical Interactions
Michele Zanoni 1 Amy Gelmi 2 Michael Higgins 2 Paul Molino 2 Kevin J Fraser 1 Robert Byrne 1 Klaudia Wagner 2 Sanjeev Gambhir 2 David L Officer 2 Gordon G Wallace 2 Dermot Diamond 1
1Dublin City University Dublin Ireland2University of Wollongong Wollongong AustraliaShow Abstract
Polythiophenes (pTTh) are an important representative class of conjugated polymers that form some of the most environmentally and thermally stable materials that can be used as electrical conductors, nonlinear optical devices, polymer LEDs, electrochromic windows, sensors, solar cells, polymer electronic interconnects, nanoelectronic and optical devices1. Gaining control over the structure, properties, and function in polythiophene derivatives is a critical subject for the development of new advanced materials. An enhancement in the electronic and photonic properties of the materials and the creation of new functions, such as new sensory materials, depends on the synthesis of the pTTh2. This leads to the exciting prospect that the properties of pTTh can be selectively engineered through synthesis and molecular assembly. Covalent incorporation of a benzospiropyran (BSP) photoactive unit with the TTh Ï?-conjugated system has been achieved achieved and the characteristics of the new pTTh-BSP hybrid polymer investigated 3. Although several recent papers reported the chelation capacity of the well-known BSP moiety with metal ions, DNA, aminoacids and proteins 4,5, a dual control (photo- and electrochemical) structure has never been tried in this context. In this work, Atomic Force Microscopy (AFM) was used to detect surface interactions between the electro-grown polymer and biomolecules, in particular fibronectin, which plays a major role in fundamental bio-processes like cell adhesion, growth and migration 6,7. This protein was chemically functionalized onto the AFM tip, and interactions with a substrate coated with the pTTh-BSP hybrid polymer before and after its photochemical activation (to the merocyanine form) by exposure to a 254 nm UV light source for 15 minutes, and following 15 minutes of deactivation with a white light source. Quartz Crystal Microbalance (QCM) measurements provided a complementary means to investigate the interactions between the polymeric surface and the protein. The results exhibited good reversibility and unique photo-selective behaviour over the whole experimental data set. Electrochemical control of the polymer state provides an additional means to control interactions with the protein, which are being investigated 1. S. Gambhir et all, Synthetic Metals, 154, 2005: 117-120 2. H. Mehenni et all, Canadian Journal of Chemistry, 86, 2008, 1010-1018. 3. K. Wagner et all, J. Am. Chem. Soc., 133 (14), 2011, 5453-5462. 4. I. Willner et all, J. Am. Chem. Soc., 115, 1993, 4937-4938. 5. S. Scarmagnani et all, J. Mater. Chem., 18, 2008, 5063â?"5071. 6. C.M. Williams et all, Cancer Research, 68 (9), 2008, 3185-3192. 7. Pflugers Arch et all, Eur J Physiol, 456, 2008, 61â?"70.
UU1: Bio-Organic Devices for Sensing and Actuation I
Tuesday AM, April 10, 2012
Marriott, Yerba Buena, Salon 6
9:30 AM - UU1.1
The Application of the Organic Electrochemical Transistor for Biodiagnostics: Integration with Cells and Enzymes
Scherrine Tria 1 Leslie H Jimison 1 Dion Khodagholy 1 George G Malliaras 1 Roisin Meabh Owens 1
1Ecole Nationale Supeacute;rieure des Mines de Saint Etienne Gardanne FranceShow Abstract
The ultimate goal for biodiagnostics is a technology that combines rapid analysis, low cost fabrication, and sensitivity, all in a miniature format. Modern diagnostics are also required to be portable for use in point of care situations, with non-invasive or minimally invasive techniques being favored. One very promising new technology that has the potential to respond to these specific requirements is the organic electrochemical transistor (OECT). The OECT is a device that consists of a conducting polymer film (the transistor channel) placed in contact with an electrolyte. Source and drain electrodes make electrical contact with the channel and measure the hole current (drain current), while a gate electrode is immersed in the electrolyte. The use of organic electronic materials combines benefits of biocompatibility, low cost fabrication, and flexibility â?" all important factors for the development of diagnostics. Most importantly, OECTs have been proven to be devices that provide a very sensitive way to detect minute ionic currents in an electrolyte, as the transistor amplifies the gate current. Here, we focus on two specific applications that showcase the unique properties of this conducting polymer device: i) a novel in vitro model for assessing pathogen attack of barrier tissue and ii) a biosensor for metabolite detection. The first takes advantage of the fact that the integrity of epithelial cells that form barrier tissue in the human body may be breached through specific attack by pathogens. We will show data demonstrating the biocompatibility of the OECTs for integration with live cells along with a comparison of existing techniques used for assessing barrier tissue integrity. We further demonstrate the development of OECTs for sensitive detection of pathogens. The second area of interest is the detection of certain key metabolites such as glucose and lactate. For this purpose we couple redox enzymes with the OECT to generate highly sensitive sensors. In this case we also take advantage of novel materials such as Ionic liquid gels to push the device development towards a wireless, wearable and non-invasive device. In summary we will demonstrate the use of organic electronic technology to push the frontiers of applied and fundamental life science research.
9:45 AM - UU1.2
Organic Electrochemical Transistors as Biosensors for Barrier Tissue Integrity
Leslie Hendrix Jimison 1 Scherrine A Tria 1 George G Malliaras 1 Roisin M Owens 1
1Ecole Nationale Supeacute;rieure des Mines de Saint Etienne Gardanne FranceShow Abstract
In this work we present the integration of organic electrochemical transistors (OECTs) with biological systems. The result is a cell-based biosensor for real time detection of barrier tissue integrity of in vitro cell models. Epithelial cell monolayers serve as functional barriers in many different parts of the body. In healthy biological systems, the flux of ions across barriers is tightly controlled. Paracellular transport (transport between cells) is regulated by protein structures that exist between neighboring cells known as tight junctions. The ability to measure the function of tight junctions is of paramount importance as it provides a wealth of information about barrier tissue and is indicative of certain disease states. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a commercially available conducting polymer. PEDOT:PSS has the ability to conduct both electronic and ionic carriers, offering an unique platform for the communication between biological systems and electronics. An OECT is a novel device in which drain current within the PEDOT:PSS channel is modulated by ionic current between the electrolyte and the polymer. The PEDOT:PSS devices are biocompatible: Caco-2 cells grown on PEDOT:PSS films form intact monolayers with fully developed tight junctions. In the present device architecture, intact cell monolayers act as a barrier to ionic gate current between the electrolyte and polymer channel. This property allows the OECT to be used to detect cell monolayer integrity and tight junction function. The introduction of EtOH to a healthy cell monolayer results in degradation of tight junction proteins, mimicking a pathogen attack on the body. This effect can be observed via OECT performance. The biosensor presented here provides a vehicle for fundamental research in the life sciences, facilitating the study of barrier tissue and factors affecting its integrity and allowing for the development of realistic in vitro cell models. Such devices have potential for use in drug and toxicity screening for medical and environmental purposes.
10:00 AM - *UU1.3
Organic Ion Bipolar Devices to Regulate Signaling of Biological Systems
Magnus Berggren 1 Klas Tybrandt 1 Erik Gabrielsson 1 Agneta Richter-Dahlfors 2 Karin Larsson 2
1Linkoping University Norrkoping Sweden2Karolinska Institutet Solna SwedenShow Abstract
In devices based on combinations of conjugated polymers and polyelectrolytes, both ions and electronic charges can function as the signal carrier. This combined transport functionality together with several unique biocompatibility features make these organic electroactive materials excellent in translating electronic addressing signals into biochemical ones. Organic electronic ion pumps, ion bipolar diodes and transistors are presented based on p- and n-type polyelectrolyte membranes and conjugated polymers. These ionic devices, and chemical integrated circuits thereof, have successfully been explored to stimulate eukaryotic cell systems, in vivo and in vitro.
10:30 AM - UU1.4
Sensitivity of a Dual Gate OFET for Biosensing: First Results with Fatty Acids
Bert Nickel 1 Georg Glasbrenner 1 Martin Goellner 1
1Ludwig-Maximilians-Universitauml;t Muuml;nchen GermanyShow Abstract
We have developed an encapsulation scheme for OFETs based on long alkane chains (TTC). A thin layer of 50 nm TTC is sufficient to allow for gating of the OFET via an ionic solution. Sensing is based on the adsorption of charged molecules to the TTC surface. We demonstrate the sensing principle using fatty acids, which adsorb to the TTC surface due to hydrophilic/hydrophobic forces. Experiments confirm that the detection can be either due to top- or bottom-gate sweeps. The sensitivity is easily 100 nM. From the density of the fatty acids on the surface, we estimate that another order of magnitude in sensitivity along with higher specificity can be obtained if a dense coverage of receptors is used for molecular binding. In this line, we show that our encapsulation is compatible with lipid bilayer coatings.
10:45 AM - UU1.5
Non-covalent Incorporation of Specific Binding Sites onto Organic Transistors for Selective Biosensing Applications
Mallory Hammock 1 Anatoliy Sokolov 1 Randall Stoltenberg 2 Zhenan Bao 1
1Stanford University Stanford USA2Stanford University Palo Alto USAShow Abstract
Organic field effect transistors (OFETs) provide unique platforms for chemical and biological detection. Such sensors offer tunability, portability, and the ability to directly transduce an analyte-binding event into an electrical signal, thus obfuscating the need for expensive labeling and detection equipment. The detection of biologically relevant molecules lends itself to this detection platform because of the inherent charge associated with many biomolecules, which can be detected by the OFET. The OFETâ?Ts unique architecture facilitates its use as a sensor, and there have been a number of literature examples where the active layer itself is sensitive to molecules of interest. However, OFET sensor applications have historically been restricted to the detection of small molecules in the vapor phase. Recently, our group demonstrated the real time detection of several small molecules in aqueous media using a water-stable organic semiconductor. These sensors were able to operate at low voltages due to the incorporation of an ultrathin dielectric layer, and were shown to be highly stable operating in aqueous conditions. Traditionally, OFET sensors have been used to detect small molecules by a fingerprinting approach. In this approach, the organic semiconductor is responsive to multiple chemical species, each of which causes a distinct change in the OFETâ?Ts electronic output. Identification of an unknown compound relies upon matching the detection profile to a previously recorded catalogue of sensor responses. However, while the threshold detection limit of these sensors has been demonstrated down to the part-per-billion (ppb) level, this fingerprinting approach suffers from a lack of true selectivity, making the sensorâ?Ts response to a mixture of analytes quite complex. Additionally, this fingerprinting approach would not be applicable to the detection of biological molecules in complex media, since the presence of extraneous ions, nucleic acids, lipids, and proteins would greatly complicate the sensorâ?Ts output, making it impossible to discern a specific binding event. In order to improve the current state of the art OFET sensors and simplify the sensorâ?Ts response to facilitate their use as biosensors, there exists a need to incorporate specific recognition sites into the transistor architecture. However, the direct chemical modification of the organic semiconductor for the addition of specific biomolecular recognition sites has been demonstrated to diminish the electronic performance of the device. Therefore, our strategy will be to incorporate recognition sites into the sensor without covalently modifying the organic semiconductor. This will be accomplished by the inclusion of additional binding sites that can be independently modified with orthogonal chemistry. By integrating a molecular probe into the transistorâ?Ts architecture, we hope to develop an array of sensors for multiplexed detection, each with a high selectivity for a chosen target.
11:30 AM - *UU1.6
Chemo and Biosensing Based on Charge Detection by Organic Field Effect Devices
Monia Demelas 1 Stefano Lai 1 Andrea Spanu 1 Massimo Barbaro 1 Piero Cosseddu 1 2 Annalisa Bonfiglio 1 2
1University of Cagliari Cagliari Italy2CNR-INFM Modena ItalyShow Abstract
The Organic Charge Modulated Field Effect Transistor (OCMFET) consists of a floating gate OTFT, biased by a control capacitor; the floating gate hosts a sensing area, where specific molecules can be anchored in order to define the selectivity of the sensor. The structure acts as charge sensor, detecting changes in the amount of charge associated to the molecules on the sensing areas caused by specific chemical and biological reactions. This change determines a charge separation in the floating gate: a surplus of charge is induced under the OTFT channel and a shift in the threshold voltage is obtained. As a consequence, the conductance of the transistor is increased or decreased, accordingly to the sign of the charge and to the transport regime. The sensors are typically realized with a p-type semiconductor (pentacene or TIPS pentacene), so a negative charge immobilized on the sensing areas determines an increase of its conductance, while a positive charge determines its decrease. This device may be also employed for detecting electrical currents, as those deriving from the electrical activity of excitable cells. This structure has been first implemented with a dielectric layer with a thickness of about 1.5 Âµm. Using gold as metal for all the electrodes, its operating voltages are in the range of tens of Volts. This structure has been successfully used as pH sensor and DNA-hybridation sensor. pHsensitivity has been successfully tested in devices whose probe areas have been functionalized with amino or carboxylic acid functional groups, which protonate and de-protonate in acid and basic solutions respectively. Depending on the pH, these functional groups set the voltage drop on the insulating layer and thus modulate the current flowing between source and drain. As a consequence, if a p-type semiconductor is used, a decrease of the conductance is obtained in acid solutions, while its increase is obtained in basic solutions. DNA hybridation tests have been carried out immobilizing a thiol-modified single-stranded DNA probe on the sensing area. When functionalization occurs, the negative charge associated to the backbone of the DNA molecule determines a shift in the threshold voltage. A further shift of the threshold voltage is obtained when hybridation with a complementary DNA single-strand occurs. A second implementation of this principle consists in a a low voltage version of the OCMFET, based on a much thinner dielectric layer. The structure and the working mechanisms of the sensors are the same described previously, but, by properly modifying the materials used in the realization process, operating voltages in the range of 1 Volt have been reached. The preliminary tests for this structure as pH and DNA sensor show an improved reproducibility in the results, suggesting a higher stability of the realized setup for the measurements in aqueous media.
12:00 PM - UU1.7
Electrical Detection of DNA-binding Enzymes at DNA-modified Carbon Nanotubes
Alon A Gorodetsky 1 David Ordinario 1 Hanfei Wang 1 2 Natalie Muren 3 Jacqueline K Barton 3 Colin Nuckolls 2
1University of California - Irvine Irvine USA2Columbia University New York USA3California Institute of Technology Pasadena USAShow Abstract
We have developed a strategy for wiring single molecules into carbon nanotube field effect transistors (CNT-FETs) via robust electrical contacts. This CNT-FET platform has enabled us to definitively elucidate the electrical properties of single DNA duplexes. Our measurements indicate that the effective conductivity of B-form DNA is comparable to that of highly oriented pyrolytic graphite and bears little sequence/length dependence. We have used such integrated devices, wherein a single DNA duplex serves as both a recognition and signal transduction element, as a platform for the electrical detection of DNA methyltransferases at the single molecular level. Indeed, we are able to electrically detect sequence-specific DNA binding by the DNA methyltransferase M. SssI, where methylation of the device-integrated DNA alters the affinity of the enzyme for the device. Our fully electrical methodology holds great promise for the general, single-molecular, real-time detection of the activity of DNA-binding enzymes.
12:15 PM - UU1.8
PE-CVD P3HT Surface Modification for Biomolecules Integration in OFET Devices
Maria Magliulo 1 Bianca Rita Pistillo 1 Mohammad Yusuf Mulla 1 Serafina Cotrone 1 Nicola Cioffi 1 Pietro Pavia 1 Luigia Sabbatini 1 Gerardo Palazzo 1 Luisa Torsi 1
1University of Bari Aldo Moro Bari ItalyShow Abstract
Organic Field Effect Transistors (OFET) based sensors are widely being studied because of their suitability for cost-effective mass fabrication on flexible substrates . The sensitivity and selectivity of OFETs can be increased by integrating biological receptors specific for the analyte to be detected [2, 3]. Although many methods for bio-molecules immobilization exist, the integration of bio-receptors on the active area of OFETs is a major challenge. In this study, radio frequency (RF, 13.56 MHz) Plasma Enhanced Chemical Vapor Deposition (PE-CVD) processes were utilized to functionalize the poly(3-hexylthiophene) (P3HT) organic semiconductor surface of Electrolyte Gated Organic Field Effect Transistor (EGOFET) devices [4, 5] with hydrophilic organic coatings characterized by â?"COOH groups. Acrylic acid vapors were used to feed the discharges. Different plasma deposition times were evaluated to optimize the deposition period and grant optimum electrical performance of the EGOFETs without affecting the bulk properties of the material. The surface chemical composition of P3HT before and after PE-CVD was measured by X-ray photoelectron spectroscopy (XPS). XPS data revealed the presence of carboxyl functionalities on the plasma treated P3HT surfaces even weeks after plasma deposition. The effect of annealing on the electrical performance of the EGOFETs before and after PE-CVD was also investigated. Carboxyl groups present on the coatings can serve as anchor sites to immobilize bio-receptors onto the EGOFET devices and further functionalize them for biosensors development. Acknowledgements â?oElectrolyte-Gated Organic Field-Effect Biosensors- BioEGOFETâ? SEVENTH FRAMEWORK PROGRAMME-THEME ICT-2009 supported all work described. References  L. Torsi et al. Anal. Chem., 70, 381A-387A (2005).  L. Torsi et al. Nature Materials, 7, 5, 412-417 (2008).  N.A. Sokolov et al. Materials today, 12, 9, 12-20, (2009).  L. Kergoat, et al. Advanced Materials, 22, 23, 2565-2569, (2010).  BR. Pistillo et al. Surface and Coatings Technology, 205, S534-S536 (2011).
12:30 PM - UU1.9
Bio-inspired Artificial Touch Receptors
Benjamin C-K Tee 1 Kevin Tien 3 Jin Jeon 1 Zhenan Bao 2
1Stanford University Stanford USA2Stanford University Stanford USA3The Cooper Union for the Advancement of Science and Art New York USAShow Abstract
Large area sensor networks have the potential to enable new generations of smart surfaces, which can respond intelligently to interactions with the physical environment, as well as to humans. Significant progress have been made in integrating resistive rubber sensor sheets with flexible organic electronic circuits with mechanical sensing. The sensitivity of an elastomer to mechanical compression can be increased using microstructured dielectrics, e.g., for use in capacitive pressure sensors . Here, we will present on a microstructured elastomer composite that exhibits several orders of magnitude change in conductivity, with a small loading threshold of < 1kPa. The sensitivity of the sensor composite can be tuned using different microstructures. The initial off-state resistance is very large >100Mohm, and thus reduces the power (current) requirements. Having a low current draw is important for ultra-large density integration of mechanical sensors, on par with human touch receptor density. Furthermore, the elastomeric nature of the composite makes it highly suitable for use on various curved surfaces, and can be intimately integrated on plastic substrates with suitable low-power organic interface circuitry.  Someya, T., Sekitani, T. & Iba, S. A large-area, flexible pressure sensor matrix with organic field-effect transistors for artificial skin applications. PNAS (2004).  Mannsfeld, S.C.B. et al. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nature Materials 9, 859â?"864 (2010).
12:45 PM - UU1.10
Ion Bipolar Membrane Diodes
Erik Oskar Gabrielsson 1 Klas Tybrandt 1 Magnus Berggren 1
1Linkouml;ping University Norrkouml;ping SwedenShow Abstract
Charged biomolecules can be transported in polymer matrices by electrophoresis. Here, we exploit this feature in miniaturized electrophoresis devices, which consists of micrometer-sized channels of ion exchange membranes. Such devices are used to deliver desired biomolecules to cells and tissues both in vitro and in vivo. To build more complex circuits where the ion current through one channel is modulated by an input signal from another channel, more complex device functions such as transistors and diodes are needed. Cation and anion exchange membranes can be regarded as the ionic equivalent to n- and p-doped semiconductors, and can thus be used to create ion transistors and diodes similar to semiconductor components. By sandwiching a cation and anion exchange membrane a bipolar membrane (BM) is obtained. BMs show similar properties as semiconductor p-n junctions, and ion transistors composed of BMs have recently been reported1, 2. Ion diodes based on BMs with good performance are however difficult to realize, as they suffer from water splitting in reverse bias and also from hysteresis upon switching from on to off mode due to ion accumulation in the BM interface. This work aims to improve the performance of micro-fabricated ion diodes composed of BMs, and specifically, to lower the hysteresis upon switching. A novel kind of ion diode is here presented, in which three BMs are connected in series. In this device ion accumulation during forward bias is avoided, which leads to minimized hysteresis effects and also enable relatively faster switching performance. The improved ion diode can thus be used together with ion transistors to construct complex ionic circuits, or as stand-alone components to create complex, dynamic and steep pH-gradients. 1. K. Tybrandt, K. C. Larsson, A. Richter-Dahlfors and M. Berggren, P Natl Acad Sci USA, 2010, 107, 9929-9932. 2. K. Tybrandt, E. O. Gabrielsson and M. Berggren, Journal of the American Chemical Society, 2011, 133, 10141-10145.
Symposium OrganizersChristopher J. Bettinger, Carnegie Mellon University
John Rogers, University of Illinois
Miha Irimia-Vladu, Johannes Kepler University
Luisa Torsi, Universita di Bari 'Aldo Moro'
Symposium Support National Science Foundation
UU4: Novel Materials for Bioelectronics
Wednesday PM, April 11, 2012
Marriott, Yerba Buena, Salon 6
2:30 AM - UU4.1
New Routes towards Melanin Bio-polymer Based Devices
Marianna Ambrico 1 Paolo F Ambrico 1 Antonio Cardone 2 Stefania R Cicco 2 Teresa Ligonzo 3 Vincenzo Augelli 3 Gianluca M Farinola 4
1CNR-Istituto di Metodologie Inorganiche e dei Plasmi, Sezione Territoriale di Bari Bari Italy2CNR-Istituto di Chimica dei Composti OrganoMetallici-UOS di Bari Bari Italy3Dipartimento Interateneo di Fisica, Universitagrave; degli Studi di Bari ldquo;Aldo Morordquo; Bari Italy4Dipartimento di Chimica, Universitagrave; degli Studi di Bari ldquo;Aldo Morordquo; Bari ItalyShow Abstract
The integration of biopolymers into hybrid electronic devices is one of the up to date issues in view of the achievement of bio-compatible devices. This mainly because of the possibility to combine the electrical and optical properties of semiconductors with the structural versatility and processing features typical of these materials. Among recent â?~hot topicsâ?T in bio-polymer research, synthetic melanin or, briefly, â?omelaninâ?, has been recently recognized as a quite intriguing macromolecule thanks to its multifunctional optoelectronic properties. Due to its large diffusion in nature and intrinsic bio-compatibility, the topical studies are focused on its implementation in a novel intriguing class of bio-polymer based devices. Compared with other polymers, melanin transport properties have been mainly enlightened, up to now, on pellets,  while optical absorption and conductivity properties have been investigated on melanin layers deposited on quartz and ITO/glass substrates [2,3]. Further optoelectronic features, although guessed quite interesting, could not be investigated up to now, due to the unavailability of suitable procedures for melanin layer deposition onto silicon substrates. The reason of this basically stems from the difference between the hydrophilic nature of the melanin and hydrophobic silicon surface, that prevent adequate melanin layers self assembling. Recently, we discovered interesting features related to data storage capabilities of melanin layers deposited on ITO/glass and silicon, never investigated so far [2,4]. In this work we aim to give an overview on the above mentioned results and specifically on the characterization of electronic transport across a novel hybrid metal/insulator/silicon (MIS) device, where synthetic melanin has been embedded as the insulating part. The melanin based MIS structures have been tailored on plasma modified p and n-type silicon surfaces and tested by capacitance â?" voltage measurements performed in different environments, starting from ambient air to vacuum. The use of pSi and nSi substrates and different measurement environment conditions has enabled to gain insight into ambipolar electrical transport mechanisms, which were unexplored so far. These results constitute a first important basic insight into melanin/Si interface and represent a significant step towards the integration of melanin-based bio-polymers in several kinds of hybrid organic polymer-based devices. References  T. Ligonzo, M. Ambrico, V. Augelli, G. Perna, L. Schiavulli, M.A. Tamma, P.F. Biagi, A. Minafra and V. Capozzi, J. Non-Cryst. Solids. 355, 2009, 1221  M.Ambrico, A.Cardone, T.Ligonzo, V.Augelli, P.F.Ambrico, S.Cicco, G.M.Farinola, M.Filannino, G.Perna and V.Capozzi, Org. Electron. 11, 2010, 1809  J.P. Bothma, J. deBoor, U.Divakar, P.E.Schwenn and P. Meredith, Adv.Mater. 20, 2008, 3539  M. Ambrico, P. F. Ambrico, A. Cardone, T. Ligonzo, R.Di Mundo, V.Augelli, G.M. Farinola, Adv. Mater. 23, 2011,3332
2:45 AM - *UU4.2
A Hybrid Ionic-electronic Biocompatible Conductor: Melanin Bioelectronics
Paul Meredith 1 Bernardus Mostert 1 Benjamin J Powell 1 Francis L Pratt 3 Graeme Hanson 1 Ian R Gentle 1 Ebinazar Namdas 1 Kristen Tandy 1 Tadeusz Sarna 2
1University of Queensland Brisbane Australia2Jagiellonian University Krakow Poland3Rutherford Appleton Laboratory Didcot United KingdomShow Abstract
Melanins are biological macromolecules found throughout nature and predominantly responsible for photo-protection in humans. They possess a unique and potentially useful set of physical and chemical properties including broad monotonic absorbance, electrical and photoconductivity, and near unity non-radiative conversion of absorbed photons . Amongst the melanin family, the eumelanins (hydroxyl-indolequinone polymers) are considered as the archetypal model of the pigment and for several decades the main interest in these materials has been from the biological and medical perspectives. However, renewed interest in melanins as advanced functional materials has emerged more recently, particularly in the context of a biological electrical interface material . For more than 30 years, the standard model for melanin in the solid-state has been as an amorphous semiconductor . This assertion was derived primarily from observations of electrical switching between high and low resistive states. Indeed, it has been argued that melanin constituted the first demonstrated electrically active organic device . Recently, it has been suggested that semiconductivity is not the correct model and multiple observations of more exotic phenomena such as apparent ambipolar behavior and humidity dependent electrical conductivity have led to the proposition of a hybrid ionic-electronic mechanism [4, 5]. In our paper we will describe recent progress on unraveling this difficult structure-property problem. We have used a combination of techniques including muon-spin relaxation (Î¼SR), electron paramagnetic resonance and conductivity measurements and confirm that melanin has characteristics of a hybrid ion (proton)-electron conductor. Its electrical physics is dominated by ionic behavior and we show that this originates from the so-called comproportionation equilibrium whereby protons are released in a hydroquinone-to-quinone reaction. We also demonstrate how this exotic behavior can be used in an all-solid-state organic electrochemical transistor to affect ion-to-electron transduction â?" a key element in bio-electronic interfacing. References:  Meredith et al, Soft Matter, 2006, 2, 37-44  Bothma et al, Adv. Mater., 2008, 20, 3539-3542  McGinnes et al, Science, 1974, 183, 853-855  The device is now housed in the Smithsonian Institute Chip Collection (http://smithsonianchips.si.edu/proctor/index.htm)  Meredith and Sarna, PCR, 2006, 19(6), 572-594
3:15 AM - *UU4.3
Diodes and Transistors Using Biological, Biodegradable or Bio-compatible Materials
Niyazi Serdar Sariciftci 1
1Johannes Kepler University of Linz Linz AustriaShow Abstract
Large area and high volume use of organic electronic devices will create a concern of biodegradation for the materials used in these technologies. Especially the transition from consumer electronics to consumable electronics will enhance this problem of electronic/plastic waste. Large area photovoltaic diodes in future shall not create enviromental problems. Therefore the use of bio-materials, bio-degrabale materials and/or bio-compatible materials will be important to explore.In this talk we will cover the organic waste DNA based optoelectronics as well as our recent results on abundant biological and bio-inspired materials used in organic electronic.
4:15 AM - UU4.4
Silk Fibroin Films for Dielectric and Photovoltaic Applications
Scott P Fillery 1 Matthew B. Dickerson 1 Nicholas M Bedford 1 Sang Nyon Kim 1 Lawrence F Drummy 1 Kristi M Singh 1 Katie Martinick 2 David L Kaplan 2 Michael F Durstock 1 Rajesh R Naik 1
1Air Force Research Laboratory Wright Patterson AFB USA2Tufts University Medford USAShow Abstract
Silk occupies a unique position in materials science, being both an ancient material (silk has been utilized by the textile industry for ~ 5000 years) and the focus of many current research efforts. Silk is attractive for modern materials research as silk from the silk worm Bombyx mori may be obtained in large quantities, at reasonable costs, and through a number of processing steps be purified and dissolved to create aqueous solutions of silk fibroin protein. Silk films produced from these fibroin solutions are notable for their optical transparency, mechanical robustness, and biocompatibility. Thin films produced from regenerated silk fibroin have recently been investigated for use as gate dielectric materials, electronic substrates for biocompatible electronics (e.g., microelectrode arrays and terahertz metamaterials), and the basis of many photonic devices (e.g., waveguides, photonic crystals). In this presentation we will review the results of two recent studies; the first investigating the influence of silk secondary structure on the dielectric loss and breakdown behavior of silk films (i.e., for possible use in capacitors) and the second exploring the use of silk fibroin as a flexible substrate for the production of poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)-based bulk heterojunction organic photovoltaic (BH-OPV) devices. Addressing growing concerns over the diminishing availability of indium-containing minerals, graphene films were explored as the transparent anode in our silk-supported BH-OPVs. The influence of various processing parameters on the dielectric strength of silk fibroin films and the efficiency of BH-OPV devices (e.g., thickness of the graphene anode) will be discussed during this presentation.
4:30 AM - *UU4.5
Organic Electronics and Materials for Flexible Electronic Skin
Zhenan Bao 1
1Stanford University Stanford USAShow Abstract
The field of organic electronics holds tremendous potential for applications that benefit from the use of organic materials, (e.g. very low cost, flexible and amendable to large-area processing techniques or roll-to-roll printing). Specifically, the design and development of sensors that take advantage of these benefits can lead to manufacturing of cheap electronic units for electronic skin as well as medicinal, food storage, and environmental monitoring applications. The ability to couple the sensory electrical output with on-chip signal processing can overcome the need for bulky, expensive equipment typically required for most optical detection methods. In order to attain commercial viability, chemical sensors based on organic electronics must continue to address the remaining issues in repeatability, reproducibility, stability, and selectivity. In this talk, I will present recent progress in materials and fabrication of chemical, biological and pressure sensors.
5:00 AM - UU4.6
Progress in Natural and Nature-inspired Materials for Organic Electronics
Eric Daniel Glowacki 1 Mihai Irimia-Vladu 2 1 Gundula Voss 3 Lucia Leonat 4 Uwe Monkowius 5 Zeynep Bozkurt 6 Gunther Schwabegger 7 Marius-Aurel Bodea 8 Helmut Sitter 7 Siegfried Bauer 2 Niyazi Serdar Sariciftci 1
1Johannes Kepler University Linz Austria2Johannes Kepler University Linz Austria3University of Bayreuth Bayreuth Germany4Politehnica University of Bucharest Bucharest Romania5Johannes Kepler University Linz Austria6Sabanci Univeristy Istanbul Turkey7Johannes Kepler University Linz Austria8Johannes Kepler University Linz AustriaShow Abstract
Natural and nature-inspired small molecule semiconductors have been recently successfully implemented in organic photovoltaics, organic light-emitting diodes, and field effect transistors, and afforded performances on par with state-of-the-art synthetic organic materials. Among the materials we have exploited are naturally-occurring indigoids, anthraquinones, carotenoids, and acridones. We have also demonstrated effective substrate materials based on natural resins as well as transistor gate dielectrics based on sugars, nucleic bases, and plant waxes. We have shown that fully-biodegradable devices and circuits featuring natural substrates, dielectric, and semiconducting layers can be fabricated. Many properties of some organic materials, such as hydrogen bonding, provide a number of new conceptual directions for molecular design and novel device architectures. We have found that natural materials with hydrogen bonding create highly-ordered films, affording semiconducting layers with high mobilities and high relative permittivity values.
5:15 AM - *UU4.7
Using Renewable Materials for Electronic Devices - From Salmon DNA LEDs to Paper e-Paper
Andrew Steckl 1
1University of Cincinnati Cincinnati USAShow Abstract
The drive to improve the performance and reduce the cost of electronics is starting to focus on the use of materials that are exotic for the electronics industry but actually readily available in other fields. In this talk the use of two such materials for various devices is described â?" DNA and paper. Both of them are natural biomaterials and are found all around us. DNA, which is present in all living species, is a very robust biopolymer with many useful optical and electrical properties. While synthetic DNA can be custom designed, it is very expensive in the quantities needed for electronic devices. Natural DNA, obtained from plants or animals, is relatively inexpensive and more widely available. Examples of natural DNA-containing opto/electronics will be described. Paper is also a very attractive material for many electronic device applications: very low cost, available in almost any size, versatile, portable and flexible. From an environmental point of view, paper is a renewable resource and is readily disposable (incineration, biodegradable). Applications of paper-based electronics currently being considered or investigated include biochips, sensors, communication circuits, batteries, smart packaging, displays. The potential advantages of paper-based devices are in many cases very compelling. For example, biochips fabricated on paper can use the capillary properties of paper to operate without the need of external power sources, greatly simplifying the design and reducing the cost. For e-reader devices, in addition to flexibility, the ideal solution for providing the look-and-feel of ink on paper is to have e-paper on paper.
5:45 AM - UU4.8
Chicken Albumen Dielectrics in Organic Field-effect Transistors
Tzung-Fang Guo 1 Jer-Wei Chang 1 Cheng-Guang Wang 1 Chong-Yu Huang 1 Tzung-Da Tsai 1 Ten-Chin Wen 2
1National Cheng Kung University Tainan Taiwan2National Cheng Kung University Tainan TaiwanShow Abstract
Organic field-effect transistors (OFETs) that use a biomaterial, chicken egg white, also called albumen, as the gate dielectrics are reported in this work. The albumen dielectrics were spin-cast on the gate electrode and then crosslinking by a sequential thermal treatment. The crosslinking albumen film (400 nm) has a flat and uniform surface topography and achieves nearly double the magnitude of the dielectric constant of poly(methyl-methacrylate) and polystyrene, and is an ideal dielectric layer for fabricating p-type (pentacene) and n-type (C60) OFETs. Pentacene and C60 based OFETs fabricated with albumen dielectrics have an on-off ratio of roughly 10^4, threshold voltage of -8.0 and 1.5 V, and mobility of 0.09 and 0.13 cm2/Vs, respectively. This study highlights the benefits of utilizing biomaterial dielectrics, made of thermally crosslinking natural proteins, in fabricating organic electronics.
UU3: Integration of Electronic Materials with Living Tissue
Wednesday AM, April 11, 2012
Marriott, Yerba Buena, Salon 6
9:00 AM - *UU3.1
Bio Organic-Based Gate Dielectric Materials for Thin Film Transistors
James G. Grote 1 Fahima Ouchen 1 Naranyan Venkat 1 Donna Joyce 1 Steve Smith 1 Perry Yaney 1
1Air Force Research Laboratory Wright-Patterson Air Force Base USAShow Abstract
Bio organic based materials, such as deoxyribonucleic acid (DNA) and silk, possess high dielectric constants, high electrical resistivities and low loss tangents. These biopolymers are proving suitable gate dielectric materials for both organic and inorganic thin film transistors. Doping with high dielectric constant nanoparticles, we have achieved a 2X increase in the dielectric constant and a 100X increase in the electrical resistivity, compared to the undoped biopolymer materials, without any increase in the loss tangent. Results of this work will be presented.
9:30 AM - UU3.2
Conducting Polymer Micro and Nano-spherical Cups for Targeted and Controlled Drug Release
Pouria Fattahi 1 Mohammad R Abidian 2 3
1Penn State University State College USA2Penn State University State College USA3Penn State University State College USAShow Abstract
Targeted and controlled release systems are being developed to solve problems associated with traditional methods of drug delivery such as burst and side effects. By employing a targeted release method, drug release rate can be tailored to the need of a specific application, while reducing side effects and improving patient compliance. Also, controlled release systems may provide protection for the activity of drugs, especially proteins, which are otherwise rapidly destroyed by the body. Conducting polymers (CPs) have been extensively used for biomedical applications; in particular, for neural interfaces and controlled drug delivery systems due to the following four characteristics: 1) their organic nature, 2) their response to electrical stimuli 3) their potential to be functionalized with biomolecules, and 4) their ionic and electronic conductivity. Here we report a novel method for fabrication of drug-loaded conducting polymer micro and nano-spherical cups (CPMNSCs) for drug delivery and controlled release. The fabrication process involves electrostatic spraying of drug-loaded biodegradable poly (lactic-co-glycolic acid) (PLGA) micro and nano-spheres on a gold substrate, followed by electrochemical polymerization of conductive polymer poly (3,4-ethylenedioxythiophene) (PEDOT) on the gold substrate and around the drug-loaded PLGA micro/nano-spheres. We can control the diameter of the PLGA spheres by controlling the electrospraying parameters such as polymer concentration, flow rate, voltage, needle gauge, and distance between the syringe and target plate. The diameters of the micro and nano-spheres range from 3Â±2Î¼m and 500Â±200nm, respectively, and wall thickness of the PEDOT spherical cups varies from 50-100nm. By changing the polymerization time, we can reproducibly control the opening size of the CPMNSCs and create either fully coated PEDOT (sphere) or partially coated PEDOT (spherical cup). We previously demonstrated that conducting polymer nanotubes could be used for the controlled release of drug via electrical stimulation (~1V). We anticipate that drug can be released from CPMNSCs in a controlled fashion by actuation of conducting polymer during electrical stimulation. In addition, we are actively investigating the ability of incorporation of anticancer agent into our CPMNSCs for the targeted drug delivery to the brain tumor.
9:45 AM - UU3.3
Electrical Control of Protein Conformation and Cell Function with Conducting Polymer Architectures
Alwin Wan 1 Emily Chandler 2 Christopher K Ober 1 Claudia Fischbach 2 Delphine Gourdon 1 George G Malliaras 3
1Cornell University Ithaca USA2Cornell University Ithaca USA3Ecole Nationale Supeacute;rieure des Mines de Saint Etienne Gardanne FranceShow Abstract
The interface between electronic materials and biological systems is central to governing the behaviour of bioelectronics systems, and organic electronics are particularly well-suited for use in such systems due to their dual ionic and electronic conductivities. In particular, electrochemically-active conducting polymers undergo many property changes as a function of redox state, some of which can directly affect the behaviour of cells and biomolecules that are adsorbed or adhered to the polymer. To this end, we have developed a technology utilizing a conducting polymer surface that offers unprecedented control over the molecular conformation of adsorbed proteins. This type of control is of substantial interest, as a proteinâ?Ts conformation is directly related to its bioactivity and function. Thus, the ability to precisely and easily control the conformation of surface-adsorbed proteins would find useful applications in basic research, medical diagnostics, and tissue engineering. We have focused in particular on the important extracellular matrix (ECM) protein fibronectin (Fn), which mediates cell adhesion, migration, differentiation, and growth, in processes ranging from embryonic development to wound healing. By applying a moderate voltage (or voltage gradient) to a device made from the conducting polymer poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonate (PEDOT:TOS), we varied the conformation of adsorbed Fn from compact, to extended, to partially unfolded (as verified by FÃ¶rster Resonance Energy Transfer imaging). Further, the full range of conformations was found to be biologically relevant, as they all supported subsequent cell culture. This device allowed us to further study cell behaviour as a function of ECM protein conformation. By establishing single conformations over large areas, we were able to study biological responses such as cell secretory behaviour and adhesion characteristics. We found that fibroblasts exhibited increased secretion of vascular endothelial growth factor (VEGF), and decreased integrin-mediated adhesion, on reduced PEDOT:TOS surfaces as compared to oxidized. We also extended our investigation into three dimensions with a porous, 3D, conducting scaffold made entirely of PEDOT, in order to study cell behaviour in a more physiologically-relevant environment. Future studies will utilize both the 2D and 3D platforms to investigate other cellular functions including: proliferation, differentiation, and secretion of other important factors. This novel bioelectronic technology provides a model platform for studying the specific role of ECM mechanics in regulating cellular functions.
10:00 AM - *UU3.4
Integration of Silk in Organic Electronic Devices
Michele Muccini 1 Jenson Amsden 2 Raffaella Capelli 1 Valentina Benfenati 1 Stefano Toffanin 1 Gianluca Generali 1 David Kaplan 2 Fiorenzo Omenetto 3 Roberto Zamboni 4
1CNR Bologna Italy2Tufts University Medford USA3Tufts University Medford USA4CNR Bologna ItalyShow Abstract
Organic light-emitting transistors (OLETs) are emerging optoelectronic devices having the structure of a thin-film transistor and the capability of light generation [1-2]. The most advanced OLETs encompass a huge technological potential for the realization of intense nanoscale light sources for a variety of applications, including miniaturized disposable photonic bio-sensing devices and highly integrated optoelectronic systems. Silk fibroin (SF) is a biocompatible and slowly biodegradable material with excellent mechanical properties and huge potential for use as biofunctional interface in electronic devices aimed at stimulating and controlling neural network activity and peripheral nerve repair. Here we show that SF films act as material interfaces that support the adherence and neurite outgrowth of dorsal root ganglion (DRG) neurons and preserve neuronal functions. In addition, we report on the integration of silk fibroin as a thin film dielectric in organic field-effect transistors (OFETs) ad organic light emitting transistors (OLETs). Both n- (perylene) and p-type (thiophene) silk-based OFETs are demonstrated. The measured electrical characteristics are consistent with those of conventional organic transistors, namely charge mobility of the order of 10-2 cm2/Vs and on/off ratio of 104. The silk-based optolectronic device also acts as a unipolar n-type OLET with a light emission power of 100nW.  M. Muccini, A bright future for organic field-effect transistors. Nature Mater. 5 (2006) 605-613.  R. Capelli, S. Toffanin, G. Generali, H. Husta, A. Facchetti and M. Muccini, Organic light-emitting transistors with an efficiency that out-performs the equivalent light-emitting diodes. Nature Mater. 9 (2010) 496-503.  R. Capelli et al., Integration of silk protein in organic and light-emitting transistors, Organic Electronics 12 (2011) 1146â?"1151
10:30 AM - UU3.5
Selective Functionalization of Graphene Edges and Planes by Peptides
Sang Nyon Kim 1 Zhifeng Kuang 1 Joseph M Slocik 1 Sharon E Jones 1 Yen H Ngo 1 Cui Yue 2 Barry L Farmer 1 Michael C McAlpine 2 Rajesh R Naik 1
1Air Force Research Labs WPAFB USA2Princeton University Princeton USAShow Abstract
The electronic property of a nanosized graphene is highly dependent on the nature of its edge and plane atoms, suggesting that precise chemical functionalization of graphene edges and planes can be useful to control the graphene electronics. The physicochemical diversity of amino acids enables one to obtain specific peptides which can recognize broad classes of materials. Over the past several years, peptides that selectively recognize abiotic materials have been identified. The ability to detect specific crystal faces, differentiate between polymorphs or site specific functionalization of anisotropic nanomaterials using the molecular recognition properties of peptides is beneficial for assembly of nanostructures. Here we demonstrate the edge- or plane-functionalization of graphene and graphene nanostrip (GNS) using peptides. The edge-binding peptide can be used to direct the assembly of gold nanoparticles onto the edges of the graphene. Molecular dynamics reveals the key peptide residues involved in the graphene edge- versus plane-specific interactions. Electronic properties of the edge or plane peptide functionalized graphene are also measured. The understanding of the edge/plane selectivity of the peptides could lead to the design of multifunctional peptides for the development of nanosized hybrid graphene systems for energy, catalysis and sensing.
11:30 AM - UU3.7
Conducting Polymer Microelectrodes Printed on Soft, Moist Hydrogels for Effective Stimulation of Muscular and Neuronal Cells
Matsuhiko Nishizawa 1 2 Yuichiro Ido 1 Daisuke Takahashi 1 Kuniaki Nagamine 1 2
1Tohoku University Sendai Japan2JST-CREST Tokyo JapanShow Abstract
This paper reports novel process for micropatterning conducting polymer electrode on hydrogels to provide a fully-organic, permeable, flexible electrode. All of the existing printing methods using screens, ink-jet systems or microstamps, require the drying of fluid inks, and thus cannot be used for printing on a moist gel substrate. In contrast, our new process is based on the electrochemical deposition of conducting polymer electrodes. A hydrogel film was placed over a Pt microelectrode fabricated on glass plate, followed by electropolymerization of poly (3,4-ethylenedioxythiophene) (PEDOT) at the interface between the Pt electrode and the hydrogel films. We found that electrochemical elastic actuation of PEDOT (Â±0.5 V vs. Ag/AgCl) was effective for nondestructively peeling off the soft gel from the master electrodes. The volume change of PEDOT may induce stress at the polymer/electrode interface, and cause detachment of the film. The present technique is versatile; PEDOT microelectrodes can be prepared on a variety of hydrogels, including agarose, glucomannan (konjac), collagen and polyvinyl alcohol or on polyHEMA (commercial soft contact lens). The print resolution depends on the polymerization time (polymerization charge), and typically around a few Î¼m. The surface resistance measured in a wet condition was ca. 300 kÎ©/square, this value being in agreement with previous reports for PEDOT. Such a moist, permeable and flexible electrode should have many unique applications such as an in-vivo lapping electrode and in-vitro cell cultivation. As an example, we can demonstrate the advantage of the present electrode for the electrical stimulation of C2C12 myotubes that is required for research on type2 diabetes . The PEDOT-hydrogel electrode was combined with myotubes-embedded fibrin sheet to induce cellular contractions. Importantly, the PEDOT electrode also contracted synchronously with the motion of the cells. Recent relating publications from our group are as follows: â?oConducting Polymer Electrodes Printed on Hydrogelâ? J. Am. Chem. Soc., 2010, 132, 13174 â?oSpatiotemporally Controlled Contraction of Micropatterned Skeletal Muscle Cells on a Hydrogel Sheetâ? Lab Chip, 2011, 11, 513.
11:45 AM - *UU3.8
Direct Polymerization of Conducting Polymers for Integrating Electronic Biomedical Devices with Living Tissue
David Charles Martin 1 3 Liangqi Ouyang 1 Chin-Chen Kuo 1 Crystal Shaw 2 Amy Griffin 2
1The University of Delaware Newark USA2The University of Delaware Newark USA3The University of Delaware Newark USAShow Abstract
We have been developing methods for the in-situ electrochemical polymerization of relatively soft, conjugated conducting polymers to directly interface a variety of hard, electronic biomedical devices with living tissue. Our primary emphasis has been on cortical implants, but we are also investigating these methods for use in peripheral nerve, liver, kidney, and lungs. We use a microcannula and a needle to grow the polymer into and around living cells. We are examining the changes that occur for different delay times after the initial implant, making it possible to reveal information about the healing process around the device. We can significantly improve electrical properties even after the formation of a mature scar. We are correlating our local observations of the morphology of the polymer and histology of the cell response by optical and electron microscopy with electrical properties using impedance spectroscopy. We are also correlating these observations with macroscopic behavioral outcomes, including the navigation of rats with in-situ polymer modified cortical electrodes through a maze.
12:15 PM - UU3.9
Merging pi-conjugated Units into Peptide Backbones: Physiologically Relevant Nanostructures as Conduits for Aqueous Energy Migration
Brian D Wall 1 Stephen R Diegelmann 1 Allix M Sanders 1 Shuming Zhang 2 Thomas J Dawidczyk 2 William L Wilson 2 Howard E Katz 2 1 Hai-Quan Mao 2 John D. Tovar 1 2
1JHU Baltimore USA2JHU Baltimore USAShow Abstract
We have recently developed synthetic approaches through which to incorporate a wide variety of pi-conjugated functionality into the backbones of water-soluble peptides, such as fluorophores and typical n-type and p-type semiconductors. These molecules can be triggered to self-assemble from aqueous media leading to the formation of 1-D nanomaterials with diameters under 10 nm and lengths of microns. These materials ultimately lead to the bulk formation of self-supporting hydrogels that can be prepared with either randomly dispersed or globally aligned nanostructure components. In this presentation we will describe the synthesis and optoelectronic characterization of these new nanomaterials using electronic spectroscopy and their integration into functional bioelectronic transistors. Prospects for using the peptide sequences to elicit biological adhesion or other specific responses will be addressed. References: (1) S. R. Diegelmann, J. M. Gorham and J. D. Tovar, â?oOne-dimensional optoelectronic nanostructures derived from the aqueous self-assembly of p-conjugated oligopeptides,â? in the Journal of the American Chemical Society, 2008 (130) 13840-13841. (10.1021/ja805491d) (2) G. S. Vadehra, B. D. Wall, S. R. Diegelmann and J. D. Tovar, â?oOn-resin dimerization incorporates a diverse array of pi-conjugated functionality within aqueous self-assembling peptide backbones,â? in Chemical Communications, 2010 (46) 3947-3949 (DOI: 10.1039/c0cc00301h) (3) B. D. Wall, S. R. Diegelmann, S. Zhang, T. J. Dawidczyk, W. L. Wilson, H. E. Katz, H.-Q. Mao and J. D. Tovar, â?oAligned macroscopic domains of optoelectronic nanostructures prepared via the shear flow assembly of peptide hydrogels,â? cover article in Advanced Materials, in press. (DOI: 10.1002/adma.20110296)
12:30 PM - UU3.10
Investigating Cell Contractile Forces on Biocompatible Conductive Films
Debora Winnie Lin 1 Zhenan Bao 1
1Stanford University Menlo Park USAShow Abstract
Single-walled carbon nanotubes (SWNTs) have shown promise for use in organic electronic applications including thin film transistors, conducting electrodes, and biosensors. There is a current need to rapidly process SWNTs from solution phase to substrates in order to produce device structures. In terms of SWNT film deposition, previous studies were able to adsorb SWNTs by drop casting, airbrush spray coating, spin coating, vacuum filtration, electrophoretic deposition, and Langmuir-Blodgett deposition. Furthermore, researchers have found that surfaces covalently functionalized with primary amines have been shown to selectively adsorb semiconducting SWNT. However, this and similar techniques are dependent upon environmentally sensitive surface modification techniques. Hence, we explored the potential of substrates modified with physisorbed polymers, poly(L-lysine) (PLL), as a possible alternative methodology. In this work, we detail a number of methods for depositing SWNTs onto various substrate materials using amine-rich PLL and other methods of covalently functionalizing the surface with primary amines. Furthermore, devices were constructed using these methods to observe if cell movement on the surface would elicit changes in the device performance. SWNT adsorption and alignment were characterized by atomic force microscopy (AFM). SWNT surface density was strongly dependent upon the adsorbed concentration of PLL on the surface, spin coating speed, and SWNT solution concentration. Another benefit for using PLL as an adhesion layer was for its biocompatibility with cells. Results from examining mitochondrial hydrogenase activity and Live/Dead fluorescence assay suggest that the PLL SWNTs spin-coat devices exhibited higher biocompatibility with NIH-3T3 fibroblast cells than the drop cast SWNTs devices possibly due to differences of substrate surface roughness. To further elucidate the effect of SWNT roughness on biocompatibility, cell morphology was observed on substrate surfaces of varying SWNT network density using a spray coating method. Additionally, to observe if cell contractile forces on the device surfaces would elicit a change in electrical performance, 2-terminal resistance measurements were taken at different stages of cell adhesion onto the surface. We envision these conducting biocompatible SWNT networks could potentially be used as biosensors to investigate cell adhesion mechanics or tissue-device interfaces for neural prosthetics.