Flexible and Transparent Metal Nanowire Microelectrode Arrays and Interconnects for Electrophysiology, Optogenetics, and Optical Mapping

Abstract

Transparent microelectrodes have recently emerged as a promising approach for crosstalk‐free multifunctional electrical and optical 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 microelectrode arrays (MEAs) and interconnects are designed to meet this demand. The nanowire networks exhibit a high optical transparency >90.0% at 550 nm, and superior mechanical stability up to 100,000 bending cycles at 5 mm radius. The Ag NWs microelectrodes preserve low normalized electrochemical impedance of 3.4–15 Ω cm2 at 1 kHz, and the interconnects demonstrate excellent sheet resistance (Rsh) of 4.1–25 Ω sq−1. In vivo histological analysis reveals that the Ag NWs structures are biocompatible. Studies on Langendorff‐perfused mouse and rat hearts demonstrate that the Ag NWs MEAs enable high‐fidelity real‐time monitoring of heart rhythm during co‐localized optogenetic pacing and optical mapping. This proof‐of‐concept work illustrates that the solution‐processed, transparent, and flexible Ag NWs structures are a promising candidate for the next‐generation of large‐area multifunctional biointerfaces for interrogating complex biological systems in basic and translational research.

Open thoracic surgical implantation of cardiac pacemakers in rodents

“…Our group has developed and tested a range of bioelectronics that stimulate and monitor cardiac electrophysiology 12,13,[16][17][18][19] . Earlier, we tested a miniature implantable pacemaker using an external jugular approach in mice 20 .…”

“…Successful implantation strongly depends on operator experience. The operators involved in our studies 12,13,[16][17][18][19] were all surgical residents who all had at least 2 years of experience in general surgery. Operators experienced in small animal dissection also achieved success with this procedure even without formal medical-level general surgery training.…”

Transparent, Low‐Impedance Inkjet‐Printed PEDOT:PSS Microelectrodes for Multimodal Neuroscience

“…[8,9] Such devices have been made possible by taking advantage of novel transparent conductive materials such as atomically thin graphene, [10,11,12] indium tin oxide (ITO), [13,14] metal grid bilayers, [15,16] or nanocomposite percolation networks. [17][18][19] However, each of these materials has significant drawbacks. Transparent electrodes based on graphene face challenges in scaling up for commercial production, due to the high cost and low yield inherent in synthesizing and transferring relatively large areas of defect-free graphene to insulating substrates.…”

Effect of Mechanical Properties of Substrates on Flexibility of Ag Nanowire Electrodes under a Large Number of Bending Cycles

“…There have been several reports on the evaluation of the mechanical properties of Ag nanowire electrodes subjected to bending [23][24][25]. For example, Jin et al reported 2 of 8 Ag nanowire transparent electrodes for application in flexible transparent heaters; bending tests were performed to confirm the flexibility of the electrodes under 100 cycles of bending [23].…”

“…There was no significant change in resistance during bending. Chen et al demonstrated Ag nanowire electrodes on a polyethylene terephthalate (PET) substrate, for application as a biosensor [24]. To confirm the mechanical stability, 100,000 bending cycles, under a 5 mm radius, were imposed on the electrodes, which resulted in a negligible change in resistance during bending.…”