Transient implantable medical bionics offer great promise in the field of smart controlled release and tissue regeneration. On-board energy storage is the ideal power system to drive them. In this work, a critical component of such a device, a biodegradable polymer electrolyte (silk fibroin-choline nitrate) has been developed. The efficiency of this electrolyte is demonstrated when deployed in a biodegradable thin-film magnesium battery. The battery, encapsulated in silk, offers a specific capacity of 0.06 mAh cm-2. The enzymatic degradation of the whole device occurs over 45 days in the buffered protease XIV solution. A programmed battery lifetime can be achieved using silk protection layers. This battery system provides a new avenue for an on-board biodegradable power source for next-generation transient medical bionics.

Wearable devices have emerged as powerful tools for personalized healthcare in spite of some challenges that limit their widespread applicability as continuous monitors of physiological information. Here, a materials-based strategy to add utility to traditional dielectric sensors by developing a conformal radiofrequency (RF) construct composed of an active layer encapsulated between two reverse-facing split ring resonators is applied. These small (down to 2 mm × 2 mm) passive dielectric sensors possess enhanced sensitivity and can be further augmented by functionalization of this interlayer material. Demonstrator devices are shown where the interlayer is: (i) a porous silk film, and (ii) a modified PNIPAM hydrogel that swells with pH or temperature. In vivo use is demonstrated by adhesion of the device on tooth enamel to detect foods during human ingestion. Such sensors can be easily multiplexed and yield data-rich temporal information during the diffusion of analytes within the trilayer structure. This format could be extended to a suite of interlayer materials for sensing devices of added use and specificity.

In natural systems, directed self-assembly of structural proteins produces complex, hierarchical materials that exhibit a unique combination of mechanical, chemical and transport properties. This controlled process covers dimensions ranging from the nano- to the macroscale. Such materials are desirable to synthesize integrated and adaptive materials and systems. We describe a bio-inspired process to generate hierarchically defined structures with multiscale morphology by using regenerated silk fibroin. The combination of protein self-assembly and microscale mechanical constraints is used to form oriented, porous nanofibrillar networks within predesigned macroscopic structures. This approach allows us to predefine the mechanical and physical properties of these materials, achieved by the definition of gradients in nano- to macroscale order. We fabricate centimetre-scale material geometries including anchors, cables, lattices and webs, as well as functional materials with structure-dependent strength and anisotropic thermal transport. Finally, multiple three-dimensional geometries and doped nanofibrillar constructs are presented to illustrate the facile integration of synthetic and natural additives to form functional, interactive, hierarchical networks.

The increased need for wearable and implantable medical devices has driven the demand for electronics that interface with living systems. Current bioelectronic systems have not fully resolved mismatches between engineered circuits and biological systems, including the resulting pain and damage to biological tissues. Here, salt/poly(ethylene glycol) (PEG) aqueous two-phase systems are utilized to generate programmable hydrogel ionic circuits. High-conductivity salt-solution patterns are stably encapsulated within PEG hydrogel matrices using salt/PEG phase separation, which route ionic current with high resolution and enable localized delivery of electrical stimulation. This strategy allows designer electronics that match biological systems, including transparency, stretchability, complete aqueous-based connective interface, distribution of ionic electrical signals between engineered and biological systems, and avoidance of tissue damage from electrical stimulation. The potential of such systems is demonstrated by generating light-emitting diode (LED)-based displays, skin-mounted electronics, and stimulators that deliver localized current to in vitro neuron cultures and muscles in vivo with reduced adverse effects. Such electronic platforms may form the basis of future biointegrated electronic systems.

The interaction between light and matter has been long explored, leading to insights based on the modulation and control of electrons and/or photons within a material. An opportunity exists in optomechanics, where the conversion of radiation into material strain and actuation is currently induced at the molecular level in liquid crystal systems, or at the microelectromechanical systems (MEMS) device scale, producing limited potential strain energy (or force) in light-driven systems. We present here flexible material composites that, when illuminated, are capable of macroscale motion, through the interplay of optically absorptive elements and low Curie temperature magnetic materials. These composites can be formed into films, sponges, monoliths, and hydrogels, and can be actuated with light at desired locations. Light-actuated elastomeric composites for gripping and releasing, heliotactic motion, light-driven propulsion, and rotation are demonstrated as examples of the versatility of this approach.