(14c) Liquid Infused-Elastomers As a Multi-Functional Material in Implantable Bioelectronics

Implantable electronics are a class of medical devices of unrealized potential for monitoring, diagnosis, and treatment of health and disease. Although some devices have been commercialized and are issued as the standard-of-care (e.g. pacemakers, cochlear implants), others like those for neuroprosthetics cannot make clinical impact until issues regarding life-time efficacy are addressed. Diminishing efficacy that occurs in long-term implantations is thought to be due to several factors including significant surgical trauma, an aggressive foreign body response, and poor material compatibility with the biological milieu (e.g. metal corrosion, biofouling, dielectric degradation). Here, we investigated if liquid-infused elastomers incorporated into bioelectronic devices can address these challenges. Such materials consist of an elastomer network (silicone) swollen and infused with water-immiscible liquids (oil). The elastomer hosts an oil layer yielding a slippery, hydrophobic surface out of phase from a surrounding aqueous environment.

After subcutaneous implantation in mice and histological analysis of tissue, oil-infused elastomers appear to be just as biocompatible as elastomer-only, a material widely used in countless medical devices. Extracted implants were analyzed for biofouling and revealed that oil-coated samples led to a substantial reduction in the number of adhered cells. When applied as coatings to electrophysiology microwires, oil-infused elastomers reduced friction and reduced insertion forces when pierced into agarose hydrogels. To examine the impact of this friction-reducing coating on surgical trauma, coated wires were inserted into explanted mouse brains. Elastomer-only coatings resulted in tissue tearing on the insertion edge, blood vessel shearing and extravascular blood cells, while tissue pierced with oil-infused elastomers did not show signs of each of these. In summary, we demonstrate oil-infused elastomers are biocompatible, reduce biofouling and reduce insertion trauma. These results warrant future studies to examine their potential for improving chronic implantation of bioelectronics.