Friction test and characterization of deformation of stifness-tunable wheels

Flexible materials are essential in bionic felds such as soft robots. However, the lack of stifness limits the mechanical performance of soft robots and makes them difcult to develop in many extreme working conditions, such as lifting and excavation operations.To address this issue, we prepared a stifness-tunable composite by dispersing low-melting-point alloy into thermosetting epoxy resin.A dramatic and rapid change in stifness was achieved by changing the state of matter at lower temperatures, and accurate control of the composite modulus was achieved by controlling the temperature.When the alloy content is at 30vol%, the tensile modulus changes 41.6 times, while the compressive modulus changes 58.9 times.By applying the composite to a fexible actuator, the initial stifness of the actuator was improved by 124 times, reaching332 mN/mm.In addition, the use of stifness-tunable materials in the wheel allowed for timely changes in the grounding area to improve friction.These fexible materials with manageable mechanical properties have wide applicability in felds including bionics, robotics, and sensing.Our fndings provide a new approach to designing and developing fexible materials with improved stifness and controllability.