In some embodiments, a polymer film includes a base composition of poly(ethylene-vinyl acetate) and a surface composition comprising hydroxy groups. In some embodiments, a polymer film includes a base layer of a first composition of poly(ethylene-vinyl acetate), a surface layer at a surface of the base layer, and a coating layer of a second composition of a copolymer of glycerol and sebacic acid. The surface layer includes surface hydroxy groups converted from acetate groups of the poly(ethylene-vinyl acetate). The second composition is attached to the surface layer by ester bonds between carboxyl groups of the copolymer and the hydroxy groups. A single-use bioreactor bag includes a polymer film including a base composition of poly(ethylene-vinyl acetate) and a surface composition comprising hydroxy groups. A method of modifying a poly(ethylene-vinyl acetate) film includes converting acetate groups at a first surface of the poly(ethylene-vinyl acetate) film to hydroxy groups.

Embodiments of the disclosure are generally directed to systems and methods for switchable electroactive devices for head-mounted displays (HMDs). In particular, a method may include (1) applying an electric field to an electroactive element of an electroactive device via electrodes of the electroactive device that are electrically coupled to the electroactive element to compress the electroactive element, which comprises a polymer material defining nanovoids, such that an average size of the nanovoids is decreased and a density of the nanovoids is increased in the electroactive element, wherein the electroactive device is positioned at a distance from a user's eye, and (2) emitting image light from an emissive device positioned such that at least a portion of the image light is incident on a surface of the electroactive device facing the user's eye.

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.

The elastomeric electrode includes: a stretchable substrate 10 having wrinkles formed on one surface thereof, the peaks C and valleys T of the wrinkles being repeated; a wrinkled metal nanoparticle layer 20 including metal nanoparticles 21 and formed by deposition of the metal nanoparticles along the wrinkles of the substrate 10; and a wrinkled monomolecular layer 30 including a monomolecular material having one or more amine groups (—NH.sub.2) and formed by deposition of the monomolecular material onto the metal nanoparticle layer 20. Also disclosed is a method for preparing the elastomeric electrode.

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.

A display device includes a scanned projector for projecting a beam of light, and a diffraction grating for dispersing the light at a plurality of angles into a waveguide, wherein at least a portion of the diffraction grating includes a nanovoided polymer. Manipulation of the nanovoid topology, such as through capacitive actuation, can be used to reversibly control the effective refractive index of the nanovoided polymer and hence the grating efficiency. The switchable grating can be used to control the amount of diffraction of an incident beam of light through the grating thereby decreasing optical loss. Various other methods, systems, apparatuses, and materials are also disclosed.

In some examples, a device includes a nanovoided polymer element, a planarization layer disposed on a surface of the nanovoided polymer element, a first electrode disposed on the planarization layer, and a second electrode. The nanovoided polymer element may be located at least in part between the first electrode and the second electrode. The planarization layer may be located between the nanovoided polymer element and the first electrode.

A composition that is easily applied, clear, well-bonded, and superhydrophobic is disclosed. In one aspect, the composition includes a hydrophobic fluorinated solvent, a binder comprising a hydrophobic fluorinated polymer, and hydrophobic fumed silica nanoparticles. Also disclosed is a structure including a substrate coated with the composition, as well as a method for making the composition and a method of coating a substrate with the composition.

A composition that is easily applied, clear, well-bonded, and superhydrophobic is disclosed. In one aspect, the composition includes a hydrophobic fluorinated solvent, a binder comprising a hydrophobic fluorinated polymer, and hydrophobic fumed silica nanoparticles. Also disclosed is a structure including a substrate coated with the composition, as well as a method for making the composition and a method of coating a substrate with the composition.