Fig. 2: Printing of liquid metal circuits on cranial surface.

a Photograph showing the printing of liquid metals on the cranial surface of a mouse. Scale bar, 1 cm. Inset: schematic illustration showing the setup of conformal printing. b Optical stereomicrograph of liquid-metal patterns printed on the cranial surface of a mouse. Scale bar, 1 mm. c Magnified view of optical stereomicrograph of liquid-metal patterns printed on the cranial surface of a mouse. Scale bar, 1 mm. d SEM of wireless cranial circuit including NFC chip, liquid-metal interconnection, and a chip antenna. Scale bar, 500 µm. e Optical stereomicrograph of the wireless cranial circuit. Scale bar, 500 µm. f Block diagram of a cranial circuit for NFC-based wireless neural recording. g Photographs of the NFC-based wireless neural recording in mouse brain through smartphone. Scale bar, 4 cm. h Representative LFP trace recorded and wirelessly transferred by NFC-based neural recording system with a cranial circuit. i Schematic illustration of a long-range wi-fi neural recording system in the mouse brain. Inset: photograph of the mouse with this wi-fi neural recording system. Scale bar, 2 cm. j Single-unit traces recorded using this integration of a wi-fi recording unit and cranial circuits for the as-implanted case (top) and the 2 weeks post-implantation (bottom).