Jammed Microgels in Deep Eutectic Solvents as a Green and Low-Cost Ink for 3D Printing of Reliable Auxetic Strain Sensors

Additive manufacturing is a promising technique for offeringnovelfunctionality to various materials by creating three-dimensional (3D)structures. However, the development of sustainable synthesis processesfor 3D printing inks or 3D-printed materials remains a major challenge.In this work, a simple two-step mixing approach is developed to preparea 3D printing ink from green, low-cost, and low-toxicity materials[commercial Carbopol and deep eutectic solvents (DESs)]. A small weightfraction of Carbopol can impart desired rheological properties tothe DES used in the 3D printing ink and also can significantly enhancethe stretchability of eutectogels up to 2500% strain. The 3D-printedauxetic structure shows a negative Poisson's ratio (within100% strain), high stretchability (300%), high sensitivity (gaugefactor of 3.1), good moisture resistance, and sufficient transparency.It can detect human motion with high skin comfort and breathability.The results of this work highlight a green, low-cost, and energy-savingstrategy to fabricate conductive microgel-based inks for 3D printingof wearable devices.

Automated summary

This research developed a simple two-step mixing approach to prepare a 3D printing ink using green, low-cost, and low-toxicity materials. The ink showed desired rheological properties and significantly enhanced the stretchability of eutectogels. The 3D-printed structure exhibited negative Poisson's ratio, high stretchability, high sensitivity, good moisture resistance, and sufficient transparency, making it suitable for detecting human motion.