Flexible and transparent silver nanowire structures for multifunctional electrical and optical biointerfacing

Abstract

Transparent microelectrodes have recently emerged as a promising approach to combine electrophysiology with optophysiology for multifunctional biointerfacing. High-performance flexible platforms that allow seamless integration with soft tissue systems for such applications are urgently needed. Here, silver nanowires (Ag NWs)-based transparent microelectrodes and interconnects are designed to meet this demand. The Ag NWs percolating networks are patterned on flexible polymer substrates using an innovative photolithography-based solution-processing technique. The resulting nanowire networks exhibit a high average optical transparency of 76.1-90.0% over the visible spectrum, low normalized electrochemical impedance of 3.4-15 Ω cm2 at 1 kHz which is even better than those of opaque solid Ag films, superior sheet resistance of 11-25 Ω sq−1, excellent mechanical stability up to 10,000 bending cycles, good biocompatibility and chemical stability. Studies on Langendorff-perfused mouse and rat hearts demonstrate that the Ag NWs microelectrodes enable high-fidelity real-time monitoring of heart rhythm during co-localized optogenetic pacing and optical mapping with negligible light-induced electrical artifacts. This proof-of-concept work illustrates that the solution-processed, transparent, and flexible Ag NWs networks are a promising candidate for the next-generation of large-area multifunctional biointerfaces for interrogating complex biological systems in basic and translational research.

Advances in Flexible Metallic Transparent Electrodes

“…[ 167 ] Chen et al were able to prove that metal grids can constitute efficient microelectrodes that allow high‐fidelity colocalized monitoring of heart rhythms during optogenetic pacing and optical mapping. [ 469 ] These examples illustrate that these mapping methods can be useful for future studies of metallic based TEs, specifically if they are used in combination with numerical simulations since they can shed the light on the influence of key parameters of their physical properties, or on their potential degradation when submitted to electrical or thermal stress.…”

Flexible Electro‐Optical Arrays for Simultaneous Multi‐Site Colocalized Spatiotemporal Cardiac Mapping and Modulation

“…The normalized impedance of the Au grid microelectrodes is comparable to previously reported flexible transparent microelectrodes at similar transmittance values, such as graphene, carbon nanotube, metal nanomesh, etc. [ 32–38 ] The dimensions of each microelectrodes in the electro‐optical array device can be reduced to 50 × 50 µm 2 (Figure S5, Supporting Information), comparable to individual cardiomyocytes (≈20 × 100 µm 2 ), [ 39,40 ] while still exhibit a moderate impedance value of 269 ± 10.2 kΩ (Figure S6, Supporting Information). This will allow tissue level cardiac electrical mapping using the MEA with cellular resolution or placing multiple microelectrodes with reduced spacing on the same m‐LED site if needed.…”

Advances in Implantable Optogenetic Technology for Cardiovascular Research and Medicine

“…During the spin coating, the concentration of Ag NWs can be changed to create different levels of transparency. Chen et al (2020) reports that the average transmittance from concentrations ranging from 20 to 10, 8.5, and 5.0 mg/mLs were: 57.7% to 76.1%, 81.3%, and 90.0% (Figure 2b). Their fabrication strategy can reach high resolutions of approximately 15 µm through photolithography, which is of the highest reported for Ag NWs.…”

“…Transparent interfaces for cardiac research have been developed as a promising tool in optical electrophysiology research (Chen et al, 2020). One-dimensional silver nanowires (Ag NWs) and gold (Au) nanomesh can be tuned in devices to be variably transparent with outstanding electrical conductivity and mechanical flexibility (Figure 2) (Lee et al, 2015 andSeo et al, 2017).…”