Significance: Soft devices offer many useful characteristics, including safe operation in close proximity to humans, the ability to adapt to their surroundings, ease of sterilization, simplicity, low cost, and light weight. Current soft devices, however, are still actuated by hard valves and electronic controls, and reliance on these components limits the use of soft devices in applications where hard structures or electronics are not compatible. This work demonstrates completely soft digital logic gates that can be integrated into soft devices and that allow computation and control within these devices, without hard valves or electronics. We demonstrate data storage, signal processing, digital-to-analog conversion, environmental sensing, and collaborative interaction between humans and soft devices.

An elastomeric device converts a constant input pressure into multiple oscillating, temporally offset output pressures.

In soft devices, complex actuation sequences and precise force control typically require hard electronic valves and microcontrollers. Existing designs for entirely soft pneumatic control systems are capable of either digital or analog operation, but not both, and are limited by speed of actuation, range of pressure, time required for fabrication, or loss of power through pull-down resistors. Using the nonlinear mechanics intrinsic to structures composed of soft materials—in this case, by leveraging membrane inversion and tube kinking—two modular soft components are developed: a piston actuator and a bistable pneumatic switch. These two components combine to create valves capable of analog pressure regulation, simplified digital logic, controlled oscillation, nonvolatile memory storage, linear actuation, and interfacing with human users in both digital and analog formats. Three demonstrations showcase the capabilities of systems constructed from these valves: 1) a wearable glove capable of analog control of a soft artificial robotic hand based on input from a human user’s fingers, 2) a human-controlled cushion matrix designed for use in medical care, and 3) an untethered robot which travels a distance dynamically programmed at the time of operation to retrieve an object. This work illustrates pathways for complementary digital and analog control of soft robots using a unified valve design.

Strong cohesive forces in protic ionic liquids (PILs) can induce a liquid nanostructure consisting of segregated polar and apolar domains. Small-angle X-ray scattering has shown that these forces can also induce medium chain length n-alkanols to self-assemble into micelle- and microemulsion-like structures in ethylammonium (EA⁺) and propylammonium (PA⁺) PILs, in contrast to their immiscibility with both water and ethanolammonium (EtA⁺) PILs. These binary mixtures are structured on two distinct length scales: one associated with the self-assembled n-alkanol aggregates and the other with the underlying liquid nanostructure. This suggests that EA⁺ and PA⁺ enable n-alkanol aggregation by acting as cosurfactants, which EtA⁺ cannot do because its terminating hydroxyl renders the cation nonamphiphilic. The primary determining factor for miscibility and self-assembly is the ratio of alkyl chain lengths of the alkanol and PIL cation, modulated by the anion type. These results show how ILs can support the self-assembly of nontraditional amphiphiles and enable the creation of new forms of soft matter.