Staff member

One of the most exploited properties of synthetic materials-and a limiting factor for the broader use of bio-based materials-is their durability and water stability, achieved through strong intermolecular interactions. However, this molecular stability also makes them persistent disruptors of ecological cycles, in contrast with biological structures, which undergo continuous molecular reconfigurations and use their environments to achieve both excellent mechanical properties and biodegradability. This study takes inspiration from chitinous cuticles to produce a biological material that uses water to gain strength and become waterproof. The process involves the vitrification of chitosan with small traces of nickel to create a dynamic network of intermolecular bonds using environmental water, resulting in a biomaterial that increases its strength when wet, an uncommon property previously observed in a few biological structures and never achieved artificially. The approach preserves the biomolecule's original chemistry and biodegradability while avoiding the strong organic solvents typically associated with bio-derived materials. The study describes the principle and demonstrates its application by manufacturing fully biodegradable and aquatically robust consumables and large objects made from Earth's second most abundant renewable molecule.

JTD

Flexible and biocompatible strain sensors are becoming increasingly important in fields such as health monitoring, wearable electronics, and environmental sensing because they offer significant advantages over conventional rigid systems. However, they lack the versatility and ecological and physiological biocompatibility necessary for broader integration within biological systems. Here, we describe the development of an inexpensive water-based plasticized chitosan-carbon black composite ink that can be used to produce conductive and biocompatible strain sensors. The ink can be applied to various surfaces, including skin, internal organs, and other biological tissues, using numerous methods, such as painting, dipping, and stamping. Furthermore, this unprecedented ability to attach and conform to biological surfaces allows the exploration of secondary sensing innovations, such as exploiting skin wrinkles to improve sensitivity. This study demonstrates that the ink exhibits a reliable change in electrical resistance in response to a wide range of motions, from subtle vibrations during speech and heartbeats to extensive articulations, like finger and elbow movements. This exceptional sensitivity range, biocompatibility, and the ink's low cost, biodegradability, and ease of removal enhance its applicability in sustainable, temporary, and customizable sensing solutions, highlighting its potential for versatile applications in human health monitoring, motion detection, and environmental sensing.

JTD Keywords: Blac, Chitin, Composites, Performance strain sensors