Human skin is a self-healing mechanosensory system that detects various mechanical contact forces efficiently through three-dimensional innervations. Here, we propose a biomimetic artificially innervated foam by embedding three-dimensional electrodes within a new low-modulus self-healing foam material. The foam material is synthesized from a one-step self-foaming process. By tuning the concentration of conductive metal particles in the foam at near-percolation, we demonstrate that it can operate as a piezo-impedance sensor in both piezoresistive and piezocapacitive sensing modes without the need for an encapsulation layer. The sensor is sensitive to an object’s contact force directions as well as to human proximity. Moreover, the foam material self-heals autonomously with immediate function restoration despite mechanical damage. It further recovers from mechanical bifurcations with gentle heating (70 °C). We anticipate that this material will be useful as damage robust human-machine interfaces.

self-repair in order to survive and thrive. Soft to hard tissues can self-regenerate when injured, including the skin and bones. [6] Some of the living tissues, such as nails and bones, can even continuously remodeling themselves, removing the damaged tissues unintentionally and replaced by newly grown tissues. However, unlike regenerative and remodeling capabilities in nature, robots are made from nonliving synthetic materials such as polymers and metals. Hence, as we develop robots to have greater autonomy and capabilities, having the ability to self-heal or self-repair is becoming more critical, if not, essential, especially from an environmental sustainability point of view. [2,[7][8][9][10][11] The term self-healing materials, also often referred to as self-mending or selfrepairing materials, are materials that can regain some or most of its original material properties when damaged. In synthetic materials, the self-healing materials repair their damage without regenerative origins. As these selfhealing materials undergo self-repair, they regain their original intended functions through the recovery of the desired material properties, without an increase in original mass.As the number of self-healing materials is growing at a rapid clip, we first establish a brief history in this review to help the reader gain a broader perspective on self-healing materials. We emphasize on self-healing materials that recover their mechanical properties, because mechanical properties often dictate the possible applications. Figure 1 highlights the various selfhealing materials from high modulus to low modulus materials that can be used for robotic applications.There are two broad classifications for self-healing materials: a) autonomic versus nonautonomic self-healing materials; b) intrinsic versus extrinsic self-healing. [8] These self-healing materials can recover their properties either autonomously, i.e., without significant external intervention, much like human tissues; or they can also heal with external intervention, such as when some external environment changes cause temperature increment or via various triggers such as mechanical stimuli. Intrinsic self-healing materials do not need external healing agents, while extrinsic self-healing materials contain external healing agents for the healing of the matrix materials. In addition to those classifications, we will provide new insights on classifying these materials further into this review.In Section 2, we discuss various types of smart biomimetic robots where self-healing materials can be beneficial. Section 3 Robots are increasingly assisting humans in performing various tasks. Like special agents with elite skills, they can venture to distant locations and adverse environments, such as the deep sea and outer space. Micro/nanobots can also act as intrabody agents for healthcare applications. Self-healing materials that can autonomously perform repair functions are useful to address the unpredictability of the environment and the increasing drive toward the autonom...

Power sources with good mechanical compliance are essential for various flexible and stretchable electronics. However, most of the current energy storage devices comprise of hazardous materials that may cause environmental pollution when improperly disposed. We show the first example of a stretchable, yet fully degradable battery made from nontoxic and environmentally friendly materials such as fruit‐based gel electrolytes and cellulose paper electrodes. The battery exhibits an areal capacity of 2.9 μAh cm−2 at 40 μA cm−2, corresponding to a maximum energy density around 4.0 μW h cm−2 at 56 μW cm−2 power density. The biomaterials constituted battery shows good mechanical tolerance to twisting, bending, and stretching while powering various electronic devices when combined with kirigami. Importantly, the entire battery disintegrates readily in phosphate buffered saline/cellulase solution. We integrate the “green” battery with various sensors in wearable healthcare devices for pulsation sensing and low‐noise surface electromyography applications.