3D-printable Sustainable Gelatin/Ethaline (GelEth) Ionic Eutectogels for Soft Wearables

The push for sustainability in soft robotics has exposed the field's reliance on non-biodegradable materials like thermosetting elastomers, driving the need for eco-friendly alternatives such as biopolymers and deep eutectic solvents (DES). When combined with biopolymers like gelatin, DES form stable, ionically conductive eutectogels, which are well-suited for capacitance- and resistance-based soft sensors. However, the lack of 3D-printing methods for these eutectogels has limited their design flexibility and application in soft robotics. In this work, we present a method and platform for 3D-printing of gelatin/ethaline (GelEth) eutectogels. Our platform, featuring a heated print head and coolable stage, was designed based on material properties and thermal simulations. We successfully 3D-printed GelEth into complex shapes. Moreover, we 3D-printed GelEth mesh structures on kinesiology tape to create on-body strain sensors for joint motion monitoring in the elbow and cervicothoracic junction, which demonstrated consistently excellent strain detection performance. The simplicity and low cost of both the developed 3D-printing platform and the fully sustainable GelEth material offer opportunities for personalized, on-demand use in disposable or reusable modes. We propose that 3D-printed GelEth has significant potential for applications in medical and rehabilitation devices, haptics, and AR/VR systems.