Advances in soft materials, miniaturized
electronics, sensors,
stimulators, radios, and battery-free power supplies are resulting
in a new generation of fully implantable organ interfaces that leverage
volumetric reduction and soft mechanics by eliminating electrochemical
power storage. This device class offers the ability to provide high-fidelity
readouts of physiological processes, enables stimulation, and allows
control over organs to realize new therapeutic and diagnostic paradigms.
Driven by seamless integration with connected infrastructure, these
devices enable personalized digital medicine. Key to advances are
carefully designed material, electrophysical, electrochemical, and
electromagnetic systems that form implantables with mechanical properties
closely matched to the target organ to deliver functionality that
supports high-fidelity sensors and stimulators. The elimination of
electrochemical power supplies enables control over device operation,
anywhere from acute, to lifetimes matching the target subject with
physical dimensions that supports imperceptible operation. This review
provides a comprehensive overview of the basic building blocks of
battery-free organ interfaces and related topics such as implantation,
delivery, sterilization, and user acceptance. State of the art examples
categorized by organ system and an outlook of interconnection and
advanced strategies for computation leveraging the consistent power
influx to elevate functionality of this device class over current
battery-powered strategies is highlighted.