Power-integrated, wireless neural recording systems on the cranium using a direct printing method for deep-brain analysis.

Conventional power-integrated wireless neural recording devices suffer from bulky, rigid batteries in head-mounted configurations, hindering the precise interpretation of the subject's natural behaviors. These power sources also pose risks of material leakage and overheating. We present the direct printing of a power-integrated wireless neural recording system that seamlessly conforms to the cranium. A quasi-solid-state Zn-ion microbattery was 3D-printed as a built-in power source geometrically synchronized to the shape of a mouse skull. Soft deep-brain neural probes, interconnections, and auxiliary electronics were also printed using liquid metals on the cranium with high resolutions. In vivo studies using mice demonstrated the reliability and biocompatibility of this wireless neural recording system, enabling the monitoring of neural activities across extensive brain regions without notable heat generation. This all-printed neural interface system revolutionizes brain research, providing bio-conformable, customizable configurations for improved data quality and naturalistic experimentation.

Transparent and Multi-Foldable Nanocellulose Paper Microsupercapacitors.

Despite the ever-increasing demand for transparent power sources in wireless optoelectronics, most of them have still relied on synthetic chemicals, thus limiting their versatile applications. Here, a class of transparent nanocellulose paper microsupercapacitors (TNP-MSCs) as a beyond-synthetic-material strategy is demonstrated. Onto semi-interpenetrating polymer network-structured, thiol-modified transparent nanocellulose paper, a thin layer of silver nanowire and a conducting polymer (chosen as a pseudocapacitive electrode material) are consecutively introduced through microscale-patterned masks (which are fabricated by electrohydrodynamic jet printing) to produce a transparent conductive electrode (TNP-TCE) with planar interdigitated structure. This TNP-TCE, in combination with solid-state gel electrolytes, enables on-demand (in-series/in-parallel) cell configurations in a single body of TNP-MSC. Driven by this structural uniqueness and scalable microfabrication, the TNP-MSC exhibits improvements in optical transparency (T = 85%), areal capacitance (0.24 mF cm-2 ), controllable voltage (7.2 V per cell), and mechanical flexibility (origami airplane), which exceed those of previously reported transparent MSCs based on synthetic chemicals.

Ultrahigh areal number density solid-state on-chip microsupercapacitors via electrohydrodynamic jet printing.

Microsupercapacitors (MSCs) have garnered considerable attention as a promising power source for microelectronics and miniaturized portable/wearable devices. However, their practical application has been hindered by the manufacturing complexity and dimensional limits. Here, we develop a new class of ultrahigh areal number density solid-state MSCs (UHD SS-MSCs) on a chip via electrohydrodynamic (EHD) jet printing. This is, to the best of our knowledge, the first study to exploit EHD jet printing in the MSCs. The activated carbon-based electrode inks are EHD jet-printed, creating interdigitated electrodes with fine feature sizes. Subsequently, a drying-free, ultraviolet-cured solid-state gel electrolyte is introduced to ensure electrochemical isolation between the SS-MSCs, enabling dense SS-MSC integration with on-demand (in-series/in-parallel) cell connection on a chip. The resulting on-chip UHD SS-MSCs exhibit exceptional areal number density [36 unit cells integrated on a chip (area = 8.0 mm × 8.2 mm), 54.9 cells cm-2] and areal operating voltage (65.9 V cm-2).