Autonomic perspiration in 3Dprinted hydrogel actuators In both biological and engineered systems, functioning at peak power output for prolonged periods of time requires thermoregulation. Here, we report a soft hydrogelbased actuator that can maintain stable body temperatures via autonomic perspiration. Using multimaterial stereolithography, we threedimensionally print fingerlike fluidic elastomer actuators having a polyNisopropylacrylamide (PNIPAm) body capped with a microporous (200 micrometers) polyacrylamide (PAAm) dorsal layer. The chemomechanical response of these hydrogel materials is such that, at low temperatures ( 30xc2xb0C), the pores dilate to enable localized perspiration in the hydraulic actuator. Such sweating actuators exhibit a 600% enhancement in cooling rate (i.e., 39.1xc2xb0C minutexe2x88x921) over similar nonsweating devices. Combining multiple finger actuators into a single device yields soft robotic grippers capable of both mechanically and thermally manipulating various heated objects. The measured thermoregulatory performance of these sweating actuators (107 watts kilogramxe2x88x921) greatly exceeds the evaporative cooling capacity found in the best animal systems (35 watts kilogramxe2x88x921) at the cost of a temporary decrease in actuation efficiency.

Actuation and stiffening in fluiddriven soft robots using lowmeltingpoint material Soft material robots offer a number of advantages over traditional rigid robots in applications including humanrobot interaction, rehabilitation and surgery. These robots can navigate around obstacles, elongate, squeeze through narrow openings or be squeezed  and they are considered to be inherently safe. The ability to stiffen compliant soft actuators has been achieved by embedding various mechanisms that are generally decoupled from the actuation principle. Miniaturisation becomes challenging due to space limitations which can in turn result in diminution of stiffening effects. Here, we propose to hydraulically actuate soft manipulators with lowmeltingpoint material and, at the same time, be able to switch between a soft and stiff state. Instead of allocating an additional stiffening chamber within the soft robot, one chamber only is used for actuation and stiffening. Low Melting Point Alloy is integrated into the actuation chamber of a singlecompartment soft robotic manipulator and the interfaced robotic syringe pump. Temperature change is enabled through embedded nichrome wires. Our experimental results show higher stiffness factors, from 9xe2x80x9312 opposing the motion of curvature, than those previously found for jamming mechanisms incorporated in separate additional chambers, in the range of 2xe2x80x938 for the same motion.