Soft robots actuated by pressurization and inflation of a pneumatic network (a "pneunet") of small channels in elastomeric materials are appealing for their ability to produce sophisticated motions with simple controls. Although current designs of pneu-nets achieve motion with large amplitudes, they do so relatively slowly (that is, over seconds). This paper describes a new design for pneu-nets that reduces the amount of gas that must be transported for inflation of the pneu-net, and thus increases its speed of actuation. A simple actuator can bend from a linear shape to a quasi-circular shape in 50 milliseconds when pressurized at ΔP = 345 kPa. At high rates of pressurization and inflation, the path along which the actuator bends depends on this rate. When inflated fully, the channels and chambers of this new pneu-net design experience only one-tenth the change in volume of that required for a motion of equal amplitude using the previous design. This small change in volume requires comparably low levels of strain in the material at maximum amplitudes of actuation, and commensurately low rates of fatigue and failure. This actuator can operate over a million cycles without significant degradation of performance. This design for soft robotic actuators combines high rates of actuation with high reliability of the actuator, and opens new areas of application for them.

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). The ordered phase is generally identified based on the existence of superlattice ordering peaks in powder X-ray diffraction (PXRD). However, after employing a widely used postsynthesis annealing treatment, we have found that claims of “ordered” catalysts were possibly/likely mixed phases of ordered intermetallics and disordered solid solutions. Here, we employed in situ heating, synchrotron-based, X-ray diffraction to quantitatively investigate the impact of a variety of annealing conditions on the degree of ordering of large ensembles of Pt3Co nanoparticles. Monte Carlo simulations suggest that Pt3Co nanoparticles have a lower order–disorder phase transition (ODPT) temperature relative to the bulk counterpart. Furthermore, we employed microscopic-level in situ heating electron microscopy to directly visualize the morphological changes and the formation of both fully and partially ordered nanoparticles at the atomic scale. In general, a higher degree of ordering leads to more active and durable electrocatalysts. The annealed Pt3Co/C with an optimal degree of ordering exhibited significantly enhanced durability, relative to the disordered counterpart, in practical membrane electrode assembly (MEA) measurements. The results highlight the importance of understanding the annealing process to maximize the degree of ordering in intermetallics to optimize electrocatalytic activity.

One strategy for actuating soft machines (e.g., tentacles, grippers, and simple walkers) uses pneumatic inflation of networks of small channels in an elastomeric material. Although the management of a few pneumatic inputs and valves to control pressurized gas is straightforward, the fabrication and operation of manifolds containing many (>50) independent valves is an unsolved problem. Complex pneumatic manifolds—often built for a single purpose—are not easily reconfigured to accommodate the specific inputs (i.e., multiplexing of many fluids, ranges of pressures, and changes in flow rates) required by pneumatic systems. This paper describes a pneumatic manifold comprising a computer-controlled braille display and a micropneumatic device. The braille display provides a compact array of 64 piezoelectric actuators that actively close and open elastomeric valves of a micropneumatic device to route pressurized gas within the manifold. The positioning and geometries of the valves and channels in the micropneumatic device dictate the functionality of the pneumatic manifold, and the use of multi-layer soft lithography permits the fabrication of networks in a wide range of configurations with many possible functions. Simply exchanging micropneumatic devices of different designs enables rapid reconfiguration of the pneumatic manifold. As a proof of principle, a pneumatic manifold controlled a soft machine containing 32 independent actuators to move a ball above a flat surface.

Using Molecular Dynamics simulations to explicitly model fluid molecules, we study the effect of solvent wetting on the behavior of polyhedral nanoparticles at a fluid-fluid interface. First, we quantify the positional and orientational free energy characteristics of an isolated nanoparticle. Our results suggest that the thickness of the interface can introduce non-trivial effects on the preferential particle orientations. A continuum model is proposed to account for the finite interfacial mixing region, and a qualitative comparison between the two approaches is presented. We examine the effect on the free energy of the system of changes in the particle's solvation preference towards one fluid, and the degree of miscibility between the two fluids. By tuning these interaction parameters, we can potentially access and favor different orientations for the particle shapes examined. Further, we extend the insights gained from single particle analyses to the attachment of two particles. Our results reveal conditions that can drive the assembly of Cuboctahedra into either 2D Puckered Honeycomb lattices or linear rod-like structures.iii BIOGRAPHICAL SKETCH

Four separate soft robotic fingers progressively curl to play notes on a keyboard. The finger‐like actuators are made of a silicone elastomer molded from 3D printed parts by G. M. Whitesides and co‐workers. On page 2163, these soft fingers are shown to be capable of bending fully in less than 50 ms, actuating over 1 million cycles, and bending along different paths based on their rate of pressurization.