Abstract
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. SilDNs simultaneously possess low elastic modulus (E100% < 700kPa) as well as large ultimate strains (dL/L0 up to ~ 400 %), toughnesses (U ~ 1.4 MJ·m−3), and strengths (σ ~ 1 MPa). Importantly, the latent condensation reaction permits cohesive bonding of printed objects to dissimilar substrates with modulus gradients that span more than seven orders of magnitude. We demonstrate soft devices relevant to a broad range of disciplines: models that simulate the geometries and mechanical properties of soft tissue systems and multimaterial assemblies for next generation wearable devices and robotics.
Highlights
1234567890():,; There are inherent advantages to devices constructed, even partially, from soft matter
The combination of low moduli and large extensibility permit versatile devices that can reversibly exhibit a wide, continuous range of deformation states[2]. In these synthetic systems, crosslinked poly(dimethylsiloxanes), commonly referred to as silicone rubbers, are ideal building materials due to their excellent mechanical properties, thermal resistance, and chemical inertness. This phenomenal performance originates from the highly flexible siloxane (Si-O-Si) backbone that imparts a high degree of molecular mobility and glass transition temperatures among the lowest found in common polymers (Tg < −100 °C)[2]
Nascent technologies based on kinetically trapping commercial resins as embedded ink within a viscous matrix offer the potential to print designs of greater complexity[8,9]
Summary
1234567890():,; There are inherent advantages to devices constructed, even partially, from soft matter. The combination of low moduli and large extensibility permit versatile devices that can reversibly exhibit a wide, continuous range of deformation states[2] In these synthetic systems, crosslinked poly(dimethylsiloxanes), commonly referred to as silicone rubbers, are ideal building materials due to their excellent mechanical properties, thermal resistance, and chemical inertness. We propose a family of silicone DNs (SilDNs) composed of a weak, but 3D-printable silicone network that ensnares the precursors to a commercially available mechanically robust RTV silicone (Fig. 1a) This materials platform can simultaneously possess low elastic moduli (100 kPa < E100% < 670 kPa) and a high elongation (dL/L0 ~ 400%), toughness (U > 1 MJ m−3), and strength (σ ~ 1 MPa) previously inaccessible in SLA elastomers. Printed objects from this family can bond to other suitable substrates (thermoplastics, thermosets, ceramics, and metals) across seven orders of magnitude in Young’s modulus (104 ⪅ E ⪅ 1011 Pa) regardless of the manufacturing process to form functional multimaterial assemblies
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