Engineering bio-based eutectogels from casein via 3D printing

Abstract

Eutectogels as an emerging class of soft-ionic materials are gaining attention in bioelectronic applications. Nevertheless, the examples of sustainable eutectogels that can be processed by 3D printing have been limited. Herein, we report the preparation of bio-based eutectogels based on casein and their processing by 3D printing. The eutectogel formulations were based on modified casein (methacrylated casein), poly(ethylene glycol) diacrylate (PEGDA), water, and two natural deep eutectic solvents (DESs) composed of betaine with either glycerol or sucrose. Different PEGDA content and DES types were evaluated to obtain bio-based eutectogels with excellent properties such as high ionic conductivity (up to 1.4 × 10⁻³ S cm⁻¹) and tunable rheological or mechanical properties. The potential of these eutectogels for bioelectronics applications was demonstrated through evaluating their performance as pressure sensors, exhibiting a sensitivity of S = 0.7 kPa⁻¹ and stable responses under repeated loading cycles. Finally, the 3D printability of casein-based eutectogels was evaluated in tomographic volumetric additive manufacturing (VAM) and digital light processing (DLP) printing technologies.