Thermally Conductive and Compliant PIB-hBN Nanocomposite Encapsulation for Soft Neural Interfaces

Soft neural interfaces require encapsulation materials that simultaneously provide mechanical compliance, thermal safety, and long-term barrier reliability, yet conventional polymers suffer from poor thermal transport, while inorganic coatings compromise flexibility. Here, we present a polyisobutylene-based nanocomposite encapsulation incorporating hexagonal boron nitride (PIB-hBN) that enhances thermal conductivity while preserving the low modulus and elastic stretchability required for soft neural implants. The PIB-hBN nanocomposite exhibits increased in-plane and through-plane thermal conductivities compared to pristine PIB, resulting in improved heat dissipation during electrically driven operation. Thermal cycling measurements using surface temperatures constrained to 37 °C show that maintaining the PIB-hBN surface allows higher heat source temperatures while remaining within safety limits during dynamic operation. Mechanical durability and moisture barrier performance are systematically evaluated, demonstrating reliability comparable to established soft encapsulation materials while offering superior thermal transport. Conformal integration with a peripheral nerve mock-up further demonstrates compatibility with implantable device architectures.