Qinai Zhao1,Ekaterina Gribkova2,Yiyang Shen1,Jilai Cui2,Noel Naughton2,Liangshu Liu1,Jaemin Seo1,Mattia Gazzola2,John Rogers3,Rhanor Gillette2,Hangbo Zhao1
University of Southern California1,University of Illinois at Urbana-Champaign2,Northwestern University3
Qinai Zhao1,Ekaterina Gribkova2,Yiyang Shen1,Jilai Cui2,Noel Naughton2,Liangshu Liu1,Jaemin Seo1,Mattia Gazzola2,John Rogers3,Rhanor Gillette2,Hangbo Zhao1
University of Southern California1,University of Illinois at Urbana-Champaign2,Northwestern University3
Three-dimensional (3D) penetrating microelectrode arrays (MEAs) serve as important interfaces with biological tissues in various fields, including neuroscience, tissue engineering, and wearable bioelectronics. These 3D MEAs can penetrate surface layers of tissues, thereby facilitating electrophysiological sensing and electrical stimulation of interior tissues in a minimally invasive manner. Stretchable penetrating MEAs are highly desirable as they can adapt to the deformations of dynamically moving tissues or organs. This adaptability enables stable bioelectronic interfacing, enhances recording signal quality, and reduces tissue damage. However, fabricating stretchable 3D MEAs with high electrode modulus required for penetration and customized geometries presents significant challenges in materials integration and patterning. In this study, we present the design, fabrication, and applications of highly stretchable microneedle electrode arrays (SMNEAs) for sensing localized intramuscular electromyography (iEMG) signals in vitro. We have developed a hybrid fabrication scheme utilizing molding, microfabrication, and transfer printing, which enables scalable fabrication of SMNEAs with high electrode modulus (E = 6.6 GPa) and device stretchability (80%). Our SMNEAs also offer controllable electrode dimensions and recording areas, and low electrode impedance. We demonstrate the use of these SMNEAs in recording iEMG signals from the buccal mass of Aplysia. By inserting a multichannel SMNEA with varying electrode lengths into individual muscle groups of the buccal mass, we achieved high-fidelity, localized iEMG recording during muscle contractions and relaxations. The iEMG signals captured by the SMNEA exhibit distinctive spatiotemporal muscle activation patterns within individual muscle groups of the buccal mass, a level of detail unachievable with surface electromyography (sEMG) using a planar MEA. The high electrode modulus and device stretchability, as well as customized electrode geometries make our SMNEAs potentially useful for local sensing and stimulation of dynamic 3D tissues such as cardiac and neuromuscular tissues.