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

• Published in: Advanced materials (Weinheim) Vol. 35; no. 12; pp. e2210206 - n/a
• Main Authors: Hiendlmeier, Lukas, Zurita, Francisco, Vogel, Jonas, Del Duca, Fulvia, Al Boustani, George, Peng, Hu, Kopic, Inola, Nikić, Marta, F. Teshima, Tetsuhiko, Wolfrum, Bernhard
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2023
• Subjects: 4D printing; cuff electrodes; Electric Conductivity; Electrodes; Electrodes, Implanted; Folding; Hydrogels; Implantation; Materials science; Moisture effects; nerve interfaces; Peripheral nerves; Peripheral Nerves - physiology; Photopolymerization; Polyurethane resins; Printing; Robustness; self‐folding; small nerves; stretchable materials; Substrates; small nerves; self-folding; stretchable materials; 4D printing; cuff electrodes; hydrogels; nerve interfaces
• DOI: 10.1002/adma.202210206
• ISSN: 0935-9648

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. An electric peripheral nerve interface that can fold itself to a cuff around small nerves during the implantation is presented. This actuation property, combined with the use of stretchable materials, makes the device robust and straightforward to use. The stimulation and recording capabilities are shown on small nerves in vivo.