Year: 2026
Type: preprint
Abstract: Polymers used as substrate and encapsulation for implants are typically deposited layer-by-layer, leaving polymer–polymer interfaces that adhere poorly and become a critical failure point. Thermoplastic polyurethane (TPU) elastomers combine four properties not found together in any other candidate: decades of clinical use in long-term implants and availability in medical grade, a stiffness well below that of polyimide and parylene C, compatibility with microfabrication, and thermoplastic self-fusion, which removes the polymer–polymer interface entirely. This work introduces TPU as a base material for soft, high-density neural interfaces and demon-strates one route to realizing them. Gold is patterned on a sacrificial copper sheet by maskless lithography and transferred into TPU by vacuum lamination, giving conformally coated tracks down to 15 µm at 30 µm pitch within a single, merged polymer body. An additional electroplating step produces a nanostructured “pinecone” gold surface that increases the electrode electrochemically active area, approximately doubling the charge injection capacity. Daisy-chain silicon chips were also embedded within the soft polymer body. The films transmit up to 88% at 470 nm, a wavelength commonly used for optogenetics. TPU showed no cytotoxicity towards differentiated SH-SY5Y cells and only a mild tissue response after 9.5 months of subcutaneous rat implantation.
Authors: Anna Pak, Andrada Iulia Velea, Tim Hosman, Joshua Wilson, Raphael Panskus, Manuel Seckel, Pablo de Anta Dardagan, Ralf Schmidt, Domonkos Horváth, Kinga Tóth, Domokos Meszéna, Astrid Gollhardt, Nasim Bakhshaee Babaroud, Barbara Pahl, Eleni Zingkou, Asimina Kolianou, Georgia Sotiropoulou, Sandeep Negi, Florian Solzbacher, Christine Kallmayer, István Ulbert, Vasiliki Giagka
Language: English
Subfield: Cellular and Molecular Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7221702368