A Geometrically Transient Material for Bioelectronic Implants

Abstract

The outstanding barrier properties of skin make it difficult to obtain reliable physiological information (especially chemical) without the use of implantable bioelectronic sensing devices to directly access the internal biology. The clinical utility of bioelectronic implants however, hinges on a key geometrical optimization problem: devices must scale-down in size to reduce surgical invasiveness while also creating enough space to integrate electronics for wireless power delivery, data exchange, and electrical/electrochemical monitoring. Here, we present a minimally invasive bioelectronic implant with a transient geometry that can be inserted subcutaneously and measures important markers, such as pH, temperature, cardiac and respiratory activity, and levels of lithium, an important element for medical applications. To produce this new class of minimally invasive and foldable implantable sensors, we developed a fabrication method that works with highly flexible substrates to enable multiple-fold miniaturization during implantation. After implantation, the implant autonomously unfolds back to its planar form for continuous wireless operation. We demonstrate the key concepts concerning implantation, operation, and removal through extensive in vitro, ex vivo, and in vivo animal experiments. Our approach allows for robust multiplexed monitoring using quick and suture-free insertion procedures and may provide a unique advantage in the transition towards personalized health profiles.