3D-printed ultra-sensitive strain sensors using biogels prepared from fish gelatin and gellan gum

The long-term sustainable development of flexible electronic devices is limited by a reliance on synthetic polymers that pose dangers for humans and potentially severe ecological problems, as well as a reliance on conventional processing methods. This work aims to exploit 3D printing to develop natural biogels composed of fish gelatin and high acyl gellan gum for use as flexible sensors. The electrical conductivity and mechanical strength were remarkably enhanced through the environmentally friendly enzyme (transglutaminase) cross-linking and non-toxic ethanol modification treatment, which allows the development of 3D printed sensors for temperature, strain, and stress sensors. The hydrogel exhibits excellent mechanical and electrical properties as strain sensors, with Young's modulus and tensile strength of 20.7 ± 1.38 kPa and 0.14 ± 0.01 MPa, respectively, and an ultimate strain of 270.54 ± 16.23 %, which is conducive to a comfortable wearing experience. Moreover, the obtained sensors exhibited ultra-low latency (6.1 ± 1.47 ms), good durability (withstanding 1000 cyclic stretching) and high monitor sensitivity (GF = 2.37 ± 0.14) to human body movements; furthermore, the biogel fabricated using this method exhibits complete biodegradation within approximately 20 days, offering innovative prospects for the advancement of eco-friendly materials.