Large-area stretchable electronics are critical for progress in wearable computing, soft robotics and inflatable structures. Recent efforts have focused on engineering electronics from soft materials-elastomers, polyelectrolyte gels and liquid metal. While these materials enable elastic compliance and deformability, they are vulnerable to tearing, puncture and other mechanical damage modes that cause electrical failure. Here, we introduce a material architecture for soft and highly deformable circuit interconnects that are electromechanically stable under typical loading conditions, while exhibiting uncompromising resilience to mechanical damage. The material is composed of liquid metal droplets suspended in a soft elastomer; when damaged, the droplets rupture to form new connections with neighbours and re-route electrical signals without interruption. Since self-healing occurs spontaneously, these materials do not require manual repair or external heat. We demonstrate this unprecedented electronic robustness in a self-repairing digital counter and self-healing soft robotic quadruped that continue to function after significant damage.

Stimuli-responsive nanomaterials are increasingly important in a variety of applications such as biosensing, molecular imaging, drug delivery and tissue engineering. For cancer detection, a paramount challenge still exists in search of methods that can illuminate tumors universally regardless of their genotypes and phenotypes. Here we capitalized on the acidic, angiogenic tumor microenvironment to achieve broad detection of tumor tissues in a wide variety of mouse cancer models. This was accomplished using ultra-pH sensitive fluorescent nanoprobes that have tunable, exponential fluorescence activation upon encountering subtle, physiologically relevant pH transitions. These nanoprobes were silent in the circulation, then dramatically activated (>300 fold) in response to neovasculature or to the low extracellular pH in tumors. Thus, we have established non-toxic, fluorescent nanoreporters that can non-linearly amplify tumor microenvironmental signals, permitting identification of tumor tissue independently of histological type or driver mutation, and detection of acute treatment responses much more rapidly than conventional imaging approaches.

Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (E). This thermal−mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (Young's modulus < 100 kPa), and the capability to undergo extreme deformations (>600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 W·m ) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 W·m) when strained. This exceptional combination of thermal and mechanical properties is enabled by a unique thermal−mechanical coupling that exploits the deformability of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power LED lamp and a swimming soft robot.liquid metal | thermal conductivity | soft materials | soft robotics | stretchable electronics

Switch it up: Tunable, pH‐responsive nanoparticles can be selectively activated in different endocytic compartments. At high pH values, micelle formation (see picture, left) quenches fluorescence by Förster resonance energy transfer. The micelles disassemble at low pH values, leading to fluorescence emission. This nonlinear on/off nanoplatform offers many exciting opportunities in diagnostic imaging and drug‐delivery applications.

No abstract