We report a transparent, bilayer-nanomesh microelectrode array for concurrent electrophysiology recording and two-photon imaging.

Nanomeshed forms of metal have emerged as a promising biocompatible electrode material for future soft bioelectronics. However, metal/electrolyte interfaces are intrinsically capacitive, severely limiting their electrochemical performance, especially for scaled electrodes, which are essential for highresolution brain mapping. Here, an innovative bilayer nanomesh approach is demonstrated to address this limitation while preserving the nanomesh advantage. Electroplating low-impedance coatings on a gold nanomesh template achieves an impedance < 30 kΩ at 1 kHz and a charge injection limit of 1 mC cm −2 for 80 × 80 µm 2 microelectrodes, a 4.3× and 12.8× improvement over uncoated electrodes, respectively, while maintaining a transparency of ≈70% at 550 nm. Systematic characterization of transmittance, impedance, charge injection limits, cyclic charge injection, and light-induced artifacts reveal an encouraging performance of the bilayer nanomesh microelectrodes. The bilayer nanomesh approach presented here is expected to enable next-generation large-scale transparent bioelectronics with broad utility in biology.

This paper presents a wirelessly powered, fully integrated system-on-a-chip (SoC) supporting 160-channel stimulation, 16-channel recording, and 48-channel bio-impedance characterization to enable partial motor function recovery through epidural spinal cord electrical stimulation. A wireless transceiver is designed to support quasi full-duplex data telemetry at a data rate of 2 Mb/s. Furthermore, a unique in situ bio-impedance characterization scheme based on time-domain analysis is implemented to derive the Randles cell electrode model of the electrode-electrolyte interface. The SoC supports concurrent stimulation and recording while the high-density stimulator array meets an output compliance voltage of up to ±10 V with versatile stimulus programmability. The SoC consumes 18 mW and occupies a chip area of 5.7 mm × 4.4 mm using 0.18 μm high-voltage CMOS process. In our in vivo rodent experiment, the SoC is used to perform wireless recording of EMG responses while stimulation is applied to enable the standing and stepping of a paralyzed rat. To facilitate the system integration, a novel thin film polymer packaging technique is developed to provide a heterogeneous integration of the SoC, coils, discrete components, and high-density flexible electrode array, resulting in a miniaturized prototype implant with a weight and form factor of 0.7 g and 0.5 cm3, respectively.

Background: Knowledge on optimal electrical stimulation (ES) modalities and regionspecific functional effects of colonic neuromodulation is lacking. We aimed to map the regional colonic motility in response to ES of (a) the colonic tissue and (b) celiac branch of the abdominal vagus nerve (CBVN) in an anesthetized porcine model. Methods: In male Yucatan pigs, direct ES (10 Hz, 2 ms, 15 mA) of proximal (pC), transverse (tC), or distal (dC) colon was done using planar flexible multi-electrode array panels and CBVN ES (2 Hz, 0.3-4 ms, 5 mA) using pulse train (PT), continuous (10 min), or square-wave (SW) modalities, with or without afferent nerve block (200 Hz, 0.1 ms, 2 mA). The regional luminal manometric changes were quantified as area under the curve of contractions (AUC) and luminal pressure maps generated. Contractions frequency power spectral analysis was performed. Contraction propagation was assessed using video animation of motility changes. Key Results: Direct colon ES caused visible local circular (pC, tC) or longitudinal (dC) muscle contractions and increased luminal pressure AUC in pC, tC, and dC (143.0 ± 40.7%, 135.8 ± 59.7%, and 142.0 ± 62%, respectively). The colon displayed prominent phasic pressure frequencies ranging from 1 to 12 cpm. Direct pC and tC ES increased the dominant contraction frequency band (1-6 cpm) power locally. Pulse train CBVN ES (2 Hz, 4 ms, 5 mA) triggered pancolonic contractions, reduced by

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