Nanomesh microelectrode Arrays on 10μm-Thick PDMS for Ultrasoft Neuroelectronics

Ultrasoft neuroelectronics are highly interesting because they enable conformal and compliant interfacing with the soft, curvilinear surface of the neural tissue. However, current ultrasoft neural interfaces are usually limited by their electrode performance and scalability for neuroelectronic applications. Here, we present multi-functional nanomesh as an approach to achieve ultrasoft microelectrode arrays (MEAs) with excellent scalability. By stacking mechanical supporting polymer, metal, and low impedance coating, here we demonstrate an Au/PEDOT:PSS bilayer-nanomesh-based MEAs on ultrathin Polydimethylsiloxane (PDMS) substrate. We have successfully fabricated 32-channel, bilayer-nanomesh-based MEAs on PDMS with total device thickness down to only 10µm. The 32-channel bilayer-nanomesh arrays have demonstrated over 90% yield on average. We also achieved low impedance of 60 kilohms at 1 kHz with site area down to 400 µm², comparable to the size of a single neuron. The performance of this bilayer-nanomesh MEAs has been characterized through bench testing. This MEA achieves excellent and stable electrochemical performance and also demonstrates good optical transparency over a broad wavelength spectrum. Other achievements of this research are hydrophilic surface modification on the MEA surface along its stability and great sterilization compatibility with ethylene oxide (EtO) sterilization which highlights the practical utilization of this novel device for advanced neural interfacing. This multi-functional bilayer-nanomesh approach provides a promising pathway toward ultrasoft neural interfaces with excellent electrochemical performance and large throughput for applications ranging from neuroscience to biomedical devices.