Acoustophoretic Liquefaction for 3D Printing Ultrahigh-Viscosity Nanoparticle Suspensions.

An acoustic liquefaction approach to enhance the flow of yield stress fluids during Digital Light Processing (DLP)-based 3D printing is reported. This enhanced flow enables processing of ultrahigh-viscosity resins (μ  > 3700 Pa s at shear rates  = 0.01 s ) based on silica particles in a silicone photopolymer.

Making bioinspired 3D-printed autonomic perspiring hydrogel actuators.

To mitigate the adverse effects of elevated temperatures, conventional rigid devices use bulky radiators, heat sinks and fans to dissipate heat from sensitive components. Unfortunately, these thermoregulation strategies are incompatible with soft robots, a growing field of technology that, like biology, builds compliant and highly deformable bodies from soft materials to enable functional adaptability. Here, we design fluidic elastomer actuators that autonomically perspire at elevated temperatures.

Autonomic perspiration in 3D-printed hydrogel actuators.

In both biological and engineered systems, functioning at peak power output for prolonged periods of time requires thermoregulation. Here, we report a soft hydrogel-based actuator that can maintain stable body temperatures via autonomic perspiration. Using multimaterial stereolithography, we three-dimensionally print finger-like fluidic elastomer actuators having a poly--isopropylacrylamide (PNIPAm) body capped with a microporous (~200 micrometers) polyacrylamide (PAAm) dorsal layer.

3D printable tough silicone double networks.

Additive manufacturing permits innovative soft device architectures with micron resolution. The processing requirements, however, restrict the available materials, and joining chemically dissimilar components remains a challenge. Here we report silicone double networks (SilDNs) that participate in orthogonal crosslinking mechanisms-photocurable thiol-ene reactions and condensation reactions-to exercise independent control over both the shape forming process (3D printing) and final mechanical properties.

3D Printing of Viscoelastic Suspensions via Digital Light Synthesis for Tough Nanoparticle-Elastomer Composites.

The rheological parameters required to print viscoelastic nanoparticle suspensions toward tough elastomers via Digital Light Synthesis (DLS) (an inverted projection stereolithography system) are reported. With a model material of functionalized silica nanoparticles suspended in a poly(dimethylsiloxane) matrix, the rheological-parameters-guided DLS can print structures seven times tougher than those formed from the neat polymers. The large yield stress and high viscosity associated with these high concentration nanoparticle suspensions, however, may prevent pressure-driven flow, a mechanism essential to stereolithography-based printing.