Inkjet-printed 3D micro-ring-electrode arrays for amperometric nanoparticle detection.

Chip-based impact electrochemistry can provide means to measure nanoparticles in solution by sensing their stochastic collisions on appropriately-polarized microelectrodes. However, a planar microelectrode array design still restricts the particle detection to the chip surface and does not allow detection in 3D environments. In this work, we report a fast fabrication process for 3D microelectrode arrays by combining ink-jet printing with laser-patterning. To this end, we printed 3D pillars from polyacrylate ink as a scaffold. Then, the metal structures are manufactured via sputtering and laser-ablation. Finally, the chip is passivated with a parylene-C layer and the electrode tips are created via laser-ablation in a vertical alignment. As a proof of principle, we employ our 3D micro-ring-electrode arrays for single impact recordings from silver nanoparticles.

4D-Printed Soft and Stretchable Self-Folding Cuff Electrodes for Small-Nerve Interfacing.

Peripheral nerve interfacing (PNI) has a high clinical potential for treating various diseases, such as obesity or diabetes. However, currently existing electrodes present challenges to the interfacing procedure, which limit their clinical application, in particular, when targeting small peripheral nerves (<200 µm). To improve the electrode handling and implantation, a nerve interface that can fold itself to a cuff around a small nerve, triggered by the body moisture during insertion, is fabricated. This folding is achieved by printing a bilayer of a flexible polyurethane printing resin and a highly swelling sodium acrylate hydrogel using photopolymerization. When immersed in an aqueous liquid, the hydrogel swells and folds the electrode softly around the nerve. Furthermore, the electrodes are robust, can be stretched (>20%), and bent to facilitate the implantation due to the use of soft and stretchable printing resins as substrates and a microcracked gold film as conductive layer. The straightforward implantation and extraction of the electrode as well as stimulation and recording capabilities on a small peripheral nerve in vivo are demonstrated. It is believed that such simple and robust to use self-folding electrodes will pave the way for bringing PNI to a broader clinical application.