A Facile Fabrication Process for Handmade Fully Polymeric Neural Interfaces.

Conventional neural interfaces are typically manufactured by photolithographic micromachining using thermoplastic insulators and noble-metal conductors. Although effective, these approaches require costly, time-intensive infrastructure, restrict material selection, and often produce devices with substantial mechanical and interfacial mismatch relative to soft neural tissue, limiting long-term performance. Here, we introduce CASPER (CAsted and Screen-Printed polymeric ElectRodes), a cleanroom-free and low-cost benchtop strategy for the fully manual fabrication of implantable neural interfaces from biocompatible polymeric materials. By combining polymer casting with manual screen printing and reusable molds, CASPER enables rapid electrode fabrication without specialized microfabrication equipment. As a proof of concept, we developed CASPER-cuff, a fully polymeric cuff electrode tailored to the swine cervical vagus nerve, integrating PDMS insulation with metal-free PEDOT:PSS conductive hydrogel active sites. CASPER-cuff exhibited tissue-compliant mechanical properties (E < 1 MPa), together with competitive electrochemical performance (|Z|@1 kHz = 3.58 ± 1.78 kΩ; cCSC = 74.98 ± 20.27 mC cm-2), demonstrating that marked simplification of manufacturing does not compromise device function. In vivo implantation further showed stable nerve coupling and reliable stimulation and recording of evoked compound action potentials, consistent with vagal B-fiber recruitment. CASPER establishes an accessible route toward customizable, fully polymeric soft neural interfaces for bioelectronic medicine.