A variable stiffening device that includes a flexible envelope having a fluid chamber, a dielectric fluid housed within the fluid chamber, and an electrode stack that includes a plurality of electrodes and one or more abrasive strips. The electrode stack is housed within the fluid chamber and is configured to receive voltage. In addition, the one or more abrasive strips are each positioned between adjacent electrodes, such that when voltage is applied to the electrode stack thereby electrostatically drawing adjacent electrodes together, the one or more abrasive strips generate frictional engagement between adjacent electrodes to actuate the variable stiffening device from a relaxed state to a rigid state.

A capacitive transducer comprising a top electrode and a bottom electrode, and a sidewall between the top electrode and the bottom electrode. The sidewall is configured to separate the top electrode and the bottom electrode by a gap. There is a high contact resistance part on one or both of a bottom side of the top electrode or a top side of the bottom electrode.

An example device includes a nanovoided polymer element, which may be located at least in part between the electrodes. In some examples, the nanovoided polymer element may include anisotropic voids, including a gas, and separated from each other by polymer walls. The device may be an electroactive device, such as an actuator having a response time for a transition between actuation states. The gas may have a characteristic diffusion time (e.g., to diffuse half the mean wall thickness through the polymer walls) that is less than the response time. The nanovoids may be sufficiently small (e.g., below 1 micron in diameter or an analogous dimension), and/or the polymer walls may be sufficiently thin, such that the gas interchange between gas in the voids and gas absorbed by the polymer walls may occur faster than the response time, and in some examples, effectively instantaneously.

Actuators having electroactive valves are described herein. The actuators can move from a first position to a second position and lock in the second position using an electroactive valve. The device can include an actuator having a fluid-impermeable membrane. The fluid-impermeable membrane can define a compartment, the compartment having a central region, an edge region extending from and fluidly connected with the central region, an electroactive valve between the central region and the edge region, and a dielectric fluid. When actuated, the actuators can force fluid through the electroactive valves and into the edge region. Once in the edge region, the electroactive valves can prevent return flow until receiving an actuation signal.

Example methods include depositing a precursor layer onto a substrate where the precursor layer includes droplets comprising a polymerizable material, inducing a phase inversion in the precursor layer to obtain a modified precursor layer including droplets of a non-polymerizable liquid within a polymerizable liquid mixture, and polymerizing the polymerizable liquid mixture to obtain a nanovoided polymer element. Examples include devices fabricated using nanovoided polymer elements fabricated using such methods, including electroactive devices such as actuators and sensors.

An optical element includes a nanovoided polymer layer having a first refractive index in an unactuated state and a second refractive index different than the first refractive index in an actuated state. Compression or expansion of the nanovoided polymer layer, for instance, can be used to reversibly control the size and shape of the nanovoids within the polymer layer and hence tune its refractive index over a range of values, e.g., during operation of the optical element. Various other apparatuses, systems, materials, and methods are also disclosed.

An example system including an electrostatic machine including a rotor plate comprising a plurality of rotor electrodes, and rotatably fixed to a shaft configured to rotate about an axis; a stator plate comprising a plurality of stator electrodes, and rotatably fixed to a housing defining the rotor plate, the stator plate, and at least a portion of the shaft; an excitation circuit electrically; a controller, comprising: a rotor feedback circuit structured to interpret a voltage response value; a rotor position characterizing circuit structured to determine a voltage injection value; and a rotor position circuit structured to determine a calibrated rotor position value in response to the rotor position value; and wherein the excitation circuit is responsive to the voltage injection value to inject a voltage on at least one of the plurality of rotor electrodes or stator electrodes.

A force feedback actuator includes a pair of electrodes and a dielectric member. The pair of electrodes are spaced apart from one another to form a gap. The dielectric member is disposed at least partially within the gap. The dielectric member includes a first portion having a first permittivity and a second portion having a second permittivity that is different from the first permittivity. The dielectric member and the pair of electrodes are configured for movement relative to each other.

An electrostatic zipping actuator includes a primary electrode, a secondary electrode overlying the primary electrode, a dielectric layer located between and abutting at least a portion of the primary electrode and the secondary electrode, and a dielectric fluid disposed at least at a junction between the dielectric layer and one of the electrodes, where an average total thickness of the dielectric layer is less than approximately 10 micrometers.

A device, such as an electroactive device, may include primary electrode and a secondary electrode overlapping at least a portion of the primary electrode. An electroactive polymer element may include a composite polymer material and is disposed between and abuts each of the primary electrode and the secondary electrode. A phase change or other deformable medium such as a liquid, a gas, or a liquid-gas mixture may be disposed as inclusions within the polymer material. The device can be actuated by the application of a voltage between the electrodes and the attendant formation of a Maxwell stress, exposing the deformable medium to a source of radiation, changing a pressure of the deformable medium, or changing a temperature of the deformable medium, e.g., about a phase transformation temperature of the phase change medium.