Soft Implantable Bioelectronics

Contemporary implantable bioelectronic devices are typically made of high-quality metals and inorganic materials. However, their rigid and flat nature, especially in their bulk state, pose critical challenges for long-term signal monitoring and feedback stimulation in vivo because of the following issues: (i) nonconformal contact with the tissue surface, (ii) mechanical modulus mismatch at the biotic-abiotic interface, and (iii) chronic immune response and potential inflammatory reactions. Therefore, to develop implantable bioelectronics with long-term stability in vivo, the mechanical properties of the devices should be extremely soft and similar to those of the tissues. Such features have been achieved by adopting ultrathin and stretchable device structures and strain-dissipative materials. More recently, multifunctional materials that feature softness, biocompatibility, biodegradability, and self-healing capabilities have been applied to various electronic implants. Herein, we provide a brief review of soft implantable bioelectronic devices, particularly those that form a conformal and robust interface with target tissues, such as the brain, heart, and peripheral nerves. Strategies for soft materials, deformable device designs, and other methods for long-term implantation are discussed.