Search for: All records

Abstract Transversely curved composite shells of liquid crystal elastomer and polyethylene terephthalate with innervated electrodes present millisecond‐scale actuation with ≈200 mW electrical power inputs at low voltages (≈1 V). The molecular orientation is aligned to direct the thermomechanical work‐content to evert the native curvature. When powered, the curved structure initially remains latent and builds up strain energy. Thereafter, the work content is released in an ms‐scale impulse. The thin‐film actuators are powered against opposing loads to perform up to 10⁻⁵J of work. High speed imaging reveals tip velocities of several 100 mm s⁻¹with powers approaching 10⁻⁴ J s⁻¹. The design eschews bistability. After snap‐through, when the power is off, the actuator spontaneously resets to its native state. The actuation profiles are functions of the geometry and the electrical pulse patterns. The latency of actuation is reduced by powering the actuators with pulses that trigger snap‐through, allow its reset to the native state, but prevent its cooling to the ambient before subsequent actuation cycles. The actuation is harnessed in sub‐gram scale robots, including water‐strider mimicking configurations and steerable robots that can navigate on compliant (sand) and hard (slippery) surfaces. A viable template for impulsive actuation using frugal electrical power emerges. 

Exploiting the interplay of anisotropic diamagnetic susceptibility of liquid crystalline monomers and site selective photopolymerization enables the fabrication of 3D freeforms with highly refined microstructures. 

Abstract Liquid crystal elastomers (LCEs) undergo a large uniaxial contraction upon thermal or optical stimulation. LCE sheets are often fabricated with a spatially patterned direction of contraction, which can sculpt the sheet into a Gauss-curved surface. Here, we instead consider LCE sheets subject to patterned stimulation intensity, leading to a control of contraction strength. We show such patterns may also sculpt a complex surface, but with the advantage that arbitrarily many surfaces may be achieved sequentially in the same sample, thus breaking the link between microstructure and shape. We first consider a monodomain LCE in which some regions are actuated and others are not. We discuss how to join actuated and unactuated regions compatibly, and use this design rule to generate patterns for cones, anti-cones, arrays of cones and a rolling bi-strip. We validate the patterns numerically via elastic shell simulations and demonstrate them experimentally via patterned photo-chemical actuation. Secondly, we consider an LCE disk with an azimuthal director profile actuated by a radially varying stimulus. We show, theoretically and numerically, how to design a stimulation profile to sculpt any surface of revolution. Such re-configurable actuation offers enticing possibilities for haptics, robotics and locomotion.