Highly Responsive Self‐Healing and Degradable Piezoelectric Soft Machines

Piezoelectric materials that are simultaneously healable, stretchable, and degradable have remained an unmet challenge, limiting advancements in wearable and implantable electronics, where devices face multidimensional mechanical deformation, causing a risk of damage. To address this critical gap, a biocompatible piezoelectric material is developed for ultrahigh piezoelectric effects with DL-alanine amino acid crystals, which is stretchable, healable, and degradable. The in situ grown DL-alanine piezoelectric crystals within an ionically cross-linked gelatin hydrogel matrix strengthen the piezoelectric properties with an ultrahigh voltage coefficient of 1.6 Vm N^-1. The combination of the piezo-ionic property and crystal alignment results in a record-breaking energy harvesting figure-of-merit value at 57.6 pm² N^-1 to deliver outstanding mili-watt level power outputs in proof-of-concept devices which can power up even several electric light bulbs. An elastically stretchable, damage resistant strain sensor is further optimized for real-time healthcare monitoring and biomechanical motion tracking. By integrating machine learning algorithms, the sensing system intelligently classifies biomechanical activities with high accuracy, enabling advanced applications in healthcare, rehabilitation, and sports monitoring.