Soft network composite materials with deterministic and bio-inspired designs

Abstract

Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices.

An elastic second skin

“…This loss of elastic recoil is not reversible by existing therapies 8 and consequently remains the universal fate of our largest and most visible organ 9 . Recent progress in materials science and engineering have yielded flexible skin interfacing technologies 10,11,12 that are functionalized in some cases for pharmaceutical delivery 13 , rapid analyte detection 14 , continuous physiological monitoring of medical conditions 15 , and wound healing 16,17,18 . Unfortunately, these advances have not focused on restoring the mechanical and aesthetic properties of the skin to match its original, youthful state.…”

Soft, thin skin-mounted power management systems and their use in wireless thermography

“…Such stretchable characteristics are qualitatively different from those afforded by simple mechanical bendability; the consequences are important because such properties allow for intimate, long-lived interfaces with the human body, such as the skin (5,6), heart (7), and the brain (8), and for development of unusual device designs that derive inspiration from biology (9,10). Many impressive examples of the utility of these concepts have emerged over the last several years, particularly in the area of biomedical devices, where work in skin-mounted technologies is now moving from laboratory demonstrations to devices with proven utility in human clinical studies (11,12) and even to recently launched commercial products (13).…”

Untethered soft robotics

“…1b). Deterministic structures achieve macroscale compliance through the selective patterning of rigid materials (for example, in meshed, coiled or truss-like architectures) into shapes that are deformable in response to certain prescribed loading directions 9,13,14 (Fig. 1bi,ii).…”