Nanoenabled Direct Contact Interfacing of Syringe-Injectable Mesh Electronics

• Published in: Nano letters Vol. 19; no. 8; pp. 5818 - 5826
• Main Authors: Lee, Jung Min, Hong, Guosong, Lin, Dingchang, Schuhmann, Thomas G, Sullivan, Andrew T, Viveros, Robert D, Park, Hong-Gyu, Lieber, Charles M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14-08-2019
• Subjects: Animals; Electrodes, Implanted; Electronics, Medical - instrumentation; Equipment Design; Injections; Mice; Pliability; Syringes; Double-sided metal input/output; flexible electronics; flexible input/output; multiplexed electrophysiology; biocompatible neural probes; chronic neural interface
• ISSN: 1530-6984; 1530-6992; 1530-6992
• DOI: 10.1021/acs.nanolett.9b03019

Polymer-based electronics with low bending stiffnesses and high flexibility, including recently reported macroporous syringe-injectable mesh electronics, have shown substantial promise for chronic studies of neural circuitry in the brains of live animals. A central challenge for exploiting these highly flexible materials for in vivo studies has centered on the development of efficient input/output (I/O) connections to an external interface with high yield, low bonding resistance, and long-term stability. Here we report a new paradigm applied to the challenging case of injectable mesh electronics that exploits the high flexibility of nanoscale thickness two-sided metal I/O pads that can deform and contact standard interface cables in high yield with long-term electrical stability. First, we describe the design and facile fabrication of two-sided metal I/O pads that allow for contact without regard to probe orientation. Second, systematic studies of the contact resistance as a function of I/O pad design and mechanical properties demonstrate the key role of the I/O pad bending stiffness in achieving low-resistance stable contacts. Additionally, computational studies provide design rules for achieving high-yield multiplexed contact interfacing in the case of angular misalignment such that adjacent channels are not shorted. Third, the in vitro measurement of 32-channel mesh electronics probes bonded to interface cables using the direct contact method shows a reproducibly high yield of electrical connectivity. Finally, in vivo experiments with 32-channel mesh electronics probes implanted in live mice demonstrate the chronic stability of the direct contact interface, enabling consistent tracking of single-unit neural activity over at least 2 months without a loss of channel recording. The direct contact interfacing methodology paves the way for scalable long-term connections of multiplexed mesh electronics neural probes for neural recording and modulation and moreover could be used to facilitate a scalable interconnection of other flexible electronics in biological studies and therapeutic applications.