Multimaterial Digital Light Processing 3D Printing of Self-Sensing and Thermoresponsive Soft Actuators

The potential of soft actuators for tasks in complex environments remains constrained by their lack of real-time proprioceptive capabilities. Here, this challenge is addressed through a multimaterial digital light processing (DLP) 3D printing strategy for constructing bilayer actuators integrating thermoresponsive actuation with strain-sensing functions. Two photocurable functional inks were developed and integrated into a single heterogeneous bilayer system via multimaterial DLP 3D printing. The passive layer consists of a dual-network ionoelastomer based on a polymerizable deep eutectic solvent (PDES) and carboxymethyl cellulose (CMC), with favorable mechanical properties (tensile strength ∼0.5 MPa) and sensitive strain-sensing performance (gauge factor = 2.11). The active layer is composed of a functionalized poly(N-isopropylacrylamide) hydrogel; the incorporation of a DES synergistically enhanced its mechanical performance (compressive strength ∼1.05 MPa) while enabling effective regulation of the lower critical solution temperature (LCST: 32-46 °C). Seamless integration and robust interfacial bonding between these heterogeneous materials were achieved by systematically optimizing the printing process. The resulting bilayer actuators demonstrated efficient and tunable thermoresponsive actuation, with programmable complex deformations realized through the structural design of the active layer. Furthermore, the integrated sensing capabilities enabled self-perception, allowing the actuator to monitor its own deformation states during actuation. This multimaterial DLP 3D printing strategy established a material and processing foundation for the construction of intelligent soft systems with proprioceptive capabilities.