Flexible high-voltage thin-film transistors (HVTFTs) operating at more than 1 kV are integrated with compliant dielectric elastomer actuators (DEA) to create a flexible array of 16 independent actuators. To allow for high-voltage operation, the HVTFT implements a zinc-tin oxide channel, a thick dielectric stack, and an offset gate. At a source-drain bias of 1 kV, the HVTFT has a 20 µA on-current at a gate voltage bias of 30 V. Their electrical characteristics enable the switching of DEAs which require drive voltages of over 1 kV, making control of an array simpler in comparison to the use of external high-voltage switching. These HVTFTs are integrated in a flexible haptic display consisting of a 4 × 4 matrix of DEAs and HVTFTs. Using a single 1.4 kV supply, each DEA is independently switched by its associated HVTFT, requiring only a 30 V gate voltage for full DEA deflection. The 4 × 4 display operates well even when bent to a 5 mm radius of curvature. By enabling DEA switching at low voltages, flexible metal-oxide HVTFTs enable complex flexible systems with dozens to hundreds of independent DEAs for applications in haptics, Braille displays, and soft robotics.

robotic systems. The ideal reconfigurable surface would change both appearance and mechanical function.We present here a novel concept to fully reshape arrays of hundreds of densely packed flexible shape memory polymer (SMP) actuators by synchronizing local Joule heating with a single pressure supply, enabling individual control of all actuators using low voltage signals. We pattern compliant heaters on thin SMP membranes in order to precisely define regions where the stiffness can be locally changed by over two orders of magnitude. By a timely synchronization of the thermal stimuli and the external pressure, each actuator can be independently, reversibly, and rapidly latched into several positions (Figure 1). This flexible matrix of latching actuators is highly versatile: in the mechanical domain, it can exert high forces, needed for instance for compliant haptic interfaces, arrays of microfluidic valves, or soft robotic grippers. The deformable surface also controls how electromagnetic waves are reflected, leading to applications in camouflage, adaptive optics, and reconfigurable radio-frequency (RF) or millimeterwave surfaces.To illustrate the potential of the active skin, we made a highresolution haptic display because this application is one of the most demanding in terms of force and displacement requirements. Dense arrays of individually addressable actuators for flexible applications are particularly challenging to realize, given the simultaneous requirements on force, displacement, speed, and power consumption for nearly any task where the device must serve a mechanical function. The rapidly growing field of soft robotics generally consists of systems with a very small number of actuators. [8] While this is in part because the compliance of soft systems enables shape adaptation with a limited number of transducers, [9] it also reflects the challenge in devising actuation strategies for scalable large matrices of densely packed soft actuators. For instance, most soft manipulators and grippers based on pneumatic actuation, [10,11] granular jamming, [12] DEAs, [13,14] DEA coupled with electro-adhesion, [15] or shape memory alloys [16] have either only one actuator, or several actuators all driven by the same control signal (e.g., a 3-finger gripper driven by a common pressure supply). [17] To allow for a larger number of independent actuators, pneumatic systems can be multiplexed, as shown by Thorsen et al., [18] but this approach has limitations, and scaling to larger A high-resolution flexible active skin with a matrix of 32 × 24 individually addressable tactile pixels on a 4 mm pitch is reported, based on shape memory polymer (SMP) actuators. The intrinsic multistable nature of SMPs, and their more than 100-fold variation in stiffness over a narrow temperature range, enables dense arrays of actuators exhibiting simultaneously large strokes and high holding forces. The control challenge of addressing a very large number of soft actuators is solved by patterning an array of miniature stretchable heaters on...

Dielectric elastomer actuators (DEAs) are an attractive form of electromechanical transducer, possessing high energy densities, an efficient design, mechanical flexibility, high speed, and noiseless operation. They have been incorporated into a variety of elegant devices, such as microfluidic devices, tunable optics, haptic displays, and minimum-energy grippers. Dielectric elastomer minimum energy structures (DEMESs) take advantage of the prestretch of the DEA to bend a non-stretchable but flexible component to perform mechanical work. The gripper is perhaps the most intuitive type of DEMES, capable of grasping objects but with only small to moderate forces. We present a novel configuration of a DEA using electrodes made of a conductive shape-memory polymer (SMP), incorporated into the design of a gripper. The SMP electrodes allow the DEA to be rigid in the cold state, offering greater holding force than a conventional gripper. Joule heating applied to the SMP electrodes softens them, allowing for electrostatic actuation. Cooling then locks in the actuated position without the need for continued power to be supplied. Additionally, the Joule heating voltage is at least one order of magnitude less than electrostatic actuation voltages, allowing for addressing of multiple actuator elements using commercially available transistors. The shape memory gripper incorporates this addressing into its design, enabling the three segments of each finger to be controlled independently.

We report arrays of latching microfluidic valves based on shape memory polymers (SMPs), and show their applications as reagent mixers and as peristaltic pumps. The valve design takes advantage of the SMP's multiple stable shapes and over a hundred-fold stiffness change with temperature to enable a) permanent zero-power latching in either open or closed positions (>15 h), as well as b) extended cyclic operation (>3000 cycles). The moving element in the valves consists of a tri-layer with a 50 μm thick central SMP layer, 25 μm thick patterned carbon-silicone (CB/PDMS) heaters underneath, and a 38 μm thick styrene ethylene butylene styrene (SEBS) impermeable film on top. Each valve of the array is individually addressable by synchronizing its integrated local Joule heating with a single external pressure supply. This architecture significantly reduces the device footprint and eliminates the need for multiplexing in microfluidic large scale integration (mLSI) systems.

In article number https://doi.org/10.1002/admt.201700102, Herbert Shea and co‐workers report a flexible active skin consisting of a matrix of 32 × 24 individually addressable tactile pixels, based on shape memory polymer (SMP) actuators with integrated stretchable heaters. The wearable sleeve weighs only 55 g, is 2 mm thick and has a 99% actuator yield. Applications in haptic displays and active camouflage are demonstrated.