Available on-demand - S.EL05.02.03
Polymer Blend Lithography—Bioinspired Scalable Fabrication of Disordered Photonic Nanostructures for Biosensing
Radwanul Siddique1,2,Vinayak Narasimhan1,Shailabh Kumar1,Hyuck Choo1,2
California Institute of Technology1,Samsung Advanced Institute of Technology2
Millions of years of evolution in the biological world has developed a plethora of micro- and nanoscopic photonic structures that are frequently superior to synthetic analogs. These biophotonic materials show interesting novel and tunable unforeseen properties with deliberately introduced disorder in their respective geometries and compositions1. Over the last decade, photonic materials with tailored -i.e. with deliberately introduced- structural disorder have also attracted considerable interest in various optical applications due to their extended spectral and angular range of effectiveness2. Most bio-inspired nanostructured devices or optical metamaterials designed to date have been demonstrated at small-scales using expensive top-down techniques. However, biological structure formation in nature utilizes several bottom-up self-assembly approaches for manufacturing hierarchical mesoscopic nanostructures (100 – 550 nm) with immense diversity. Despite recent efforts aimed at increasing top-down fabrication writing speed, alternative routes based on self-assemblies still possess major advantages for industrial implementation of disordered structures as they allow rapid processing over large areas (>>cm2).
In this communication, we show that up-scalable polymer blend lithography technique can be used as a versatile platform for fabricating 2D planar, disordered nanostructures that can be exploited in both top-down and bottom-up strategies. Polymer blend lithography utilizes the polymer-phase separation process following nature’s way of forming nanostructures. The tailored disorder is achieved here by adjusting the process parameters (polymer blend composition and deposition conditions), enabling us to tune the morphology and the spatial distribution of the nanostructures produced, and in turn their light management properties.
First, we use our approach to pattern a resist etching mask, employed for transferring disordered nanopillars by dry etching (top-down route) onto a Fabry-Perot-resonator-based intraocular pressure (IOP) sensor for glaucoma management3. The nanostructure integration onto the IOP sensor led to a 2.5-fold improvement in readout angle allowing easy handheld monitoring and in a one-month in vivo study conducted in rabbits, showed a 3-fold reduction in IOP error and 12-fold reduction in tissue encapsulation and inflammation, compared to an IOP sensor without nanostructures. Second, we demonstrate that similar structures can serve as a template in a bottom-up configuration, whereby aluminum thin film is directly deposited into the disordered nanoholes to form scalable plasmonic metasurfaces4. These metasurfaces generate hybrid multipolar lossless plasmonic modes resulting in a broadband fluorescence-enhancement factor above 1000 for visible wavelengths with respect to glass chips commonly used in bioassays. Using the metasurface and a multiplexing technique involving three visible wavelengths, we successfully detected three biomarkers, insulin, vascular endothelial growth factor, and thrombin relevant to diabetes, ocular and cardiovascular diseases, respectively, in a single 10-μL droplet containing only 1 femtomole of each biomarker.
1. Kolle, M. and Lee, S., Progress and opportunities in soft photonics and biologically inspired optics. Advanced Materials 30(2), 2018.
2. Wiersma, D.S., Disordered photonics. Nature Photonics 7(3), 2013.
3. Narasimhan, V., Siddique, R.H., Lee, J.O., Kumar, S., Ndjamen, B., Du, J., Hong, N., Sretavan, D. and Choo, H., Multifunctional biophotonic nanostructures inspired by the longtail glasswing butterfly for medical devices. Nature Nanotechnology 13(6), 2018.
4. Siddique, R.H., Kumar, S., Narasimhan, V., Kwon, H., and Choo, H., Aluminum Metasurface With Hybrid Multipolar Plasmons for 1000-Fold Broadband Visible Fluorescence Enhancement and Multiplexed Biosensing. ACS Nano, 2019.