Room temperature 3D printing of super-soft and solvent-free elastomers

Abstract

Super-soft elastomers derived from bottlebrush polymers show promise as advanced materials for biomimetic tissue and device applications, but current processing strategies are restricted to simple molding. Here, we introduce a design concept that enables the three-dimensional (3D) printing of super-soft and solvent-free bottlebrush elastomers at room temperature. The key advance is a class of inks comprising statistical bottlebrush polymers that self-assemble into well-ordered body-centered cubic sphere phases. These soft solids undergo sharp and reversible yielding at 20°C in response to shear with a yield stress that can be tuned by manipulating the length scale of microphase separation. The addition of a soluble photocrosslinker allows complete ultraviolet curing after extrusion to form super-soft elastomers with near-perfect recoverable elasticity well beyond the yield strain. These structure–property design rules create exciting opportunities to tailor the performance of 3D-printed elastomers in ways that are not possible with current materials and processes.

Printing Reconfigurable Bundles of Dielectric Elastomer Fibers

“…Significant improvements could be realized by increasing the dielectric constant and breakdown field of the matrix [65] and additives used. [66,67] For example, block copolymers [68,69] and microgels [70] can be used as printable shear-thinning materials with lower shear moduli (µ) to increase the actuation strains. This analytical model also reveals that solid-core, coaxial DEFs are not susceptible to electromechanical instability that typically leads to failure of hollow-core DEFs [47] and planar DEAs [60][61][62] (Figure 3e).…”

Bottlebrush polymer gels: architectural control over swelling and osmotic bulk modulus

“…Progress in chemical synthesis allowed for a wide variety polymers and copolymers with elaborately controlled branched architectures [12][13][14][15] that can, in turn, serve as precursors for more complex constructs, e.g., swelling networks with branched strands that could mimic elements of natural systems. 16 Covalent cross-linking of comb-shaped polymers or molecular brushes gives rise to solvent-free elastomeric networks 17,18 or polymer gels with novel unusual mechanical properties that can be tuned by proper variation in the architectural codon of the constituent strands (polymerization degrees of the main chains, i.e., cross-linking density, and side chains as well as grafting density). Such materials exhibit very unusual mechanical properties, and allow for independent tuning of elastic moduli in a wide deformation range.…”

Challenges and Opportunities in 3D Printing of Biodegradable Medical Devices by Emerging Photopolymerization Techniques

“…[82,83] More polymeric topologies (i.e., bottlebrush and hyperbranched polymers) that are rarely reported for photopolymerization 3D printing but exhibit potentially low intrinsic viscosity could also be investigated. [84,85] Random and block copolymerizations can provide various opportunities for further tuning the mechanical properties of the crosslinked networks. In addition to rational chemical design, machine learning and data mining [86,87] are useful tools.…”