ItemMolecularly-Engineered, 4D-Printed Liquid Crystal Elastomer Actuators(WILEY-VCH Verlag GmbH, 2018-11-27) Saed, Mohand O.; Ambulo, Cedric P.; Kim, Hyun; De, Rohit; Raval, Vyom; Searles, Kyle; Siddiqui, Danyal A.; Cue, John Michael O.; Stefan, Mihaela C.; Shankar, M. Ravi; Ware, Taylor H.; 0000-0001-5154-6378 (Saed MO); 0000-0001-7996-7393 (Ware, TH); Saed, Mohand O.; Ambulo, Cedric P.; Kim, Hyun; De, Rohit; Raval, Vyom; Searles, Kyle; Siddiqui, Danyal A.; Cue, John Michael O.; Stefan, Mihaela C.; Ware, Taylor H.Three-dimensional structures that undergo reversible shape changes in response to mild stimuli enable a wide range of smart devices, such as soft robots or implantable medical devices. Herein, a dual thiol-ene reaction scheme is used to synthesize a class of liquid crystal (LC) elastomers that can be 3D printed into complex shapes and subsequently undergo controlled shape change. Through controlling the phase transition temperature of polymerizable LC inks, morphing 3D structures with tunable actuation temperature (28 ± 2 to 105 ± 1 °C) are fabricated. Finally, multiple LC inks are 3D printed into single structures to allow for the production of untethered, thermo-responsive structures that sequentially and reversibly undergo multiple shape changes. ItemMolecularly-ordered Hydrogels with Controllable, Anisotropic Stimulus Response(Royal Society of Chemistry, 2019-05-03) Boothby, Jennifer M.; Samuel, Jeremy; Ware, Taylor H.; 0000-0001-7996-7393 (Ware, TH); 0000-0003-3095-0640 (Boothby, JM); Boothby, Jennifer M.; Samuel, Jeremy; Ware, Taylor H.Hydrogels which morph between programmed shapes in response to aqueous stimuli are of significant interest for biosensors and artificial muscles, among other applications. However, programming hydrogel shape change at small size scales is a significant challenge. Here we use the inherent ordering capabilities of liquid crystals to create a mechanically anisotropic hydrogel; when coupled with responsive comonomers, the mechanical anisotropy in the network guides shape change in response to the desired aqueous condition. Our synthetic strategy hinges on the use of a methacrylic chromonic liquid crystal monomer which can be combined with a non-polymerizable chromonic of similar structure to vary the magnitude of shape change while retaining liquid crystalline order. This shape change is directional due to the mechanical anisotropy of the gel, which is up to 50% stiffer along the chromonic stack direction than perpendicular. Additionally, we show that the type of stimulus to which these anisotropic gels respond can be switched by incorporating responsive, hydrophilic comonomers without destroying the nematic phase or alignment. The utility of these properties is demonstrated in polymerized microstructures which exhibit Gaussian curvature in response to high pH due to emergent ordering in a micron-sized capillary. © 2019 The Royal Society of Chemistry. ItemResponsive, 3d Electronics Enabled by Liquid Crystal Elastomer Substrates(American Chemical Society, 2019-05-09) Kim, Hyun; Gibson, J.; Maeng, Jimin; Saed, Mohand O.; Pimentel, K.; Rihani, Rashed T.; Pancrazio, Joseph J.; Georgakopoulos, S. V.; Ware, Taylor H.; 0000-0001-7996-7393 (Ware, TH); Kim, Hyun; Maeng, Jimin; Saed, Mohand O.; Rihani, Rashed T.; Pancrazio, Joseph J.; Ware, Taylor H.Traditional electronic devices are rigid, planar, and mechanically static. The combination of traditional electronic materials and responsive polymer substrates is of significant interest to provide opportunities to replace conventional electronic devices with stretchable, 3D, and responsive electronics. Liquid crystal elastomers (LCEs) are well suited to function as such dynamic substrates because of their large strain, reversible stimulus response that can be controlled through directed self-assembly of molecular order. Here, we discuss using LCEs as substrates for electronic devices that are flat during processing but then morph into controlled 3D structures. We design and demonstrate processes for a variety of electronic devices on LCEs including deformation-tolerant conducting traces and capacitors and cold temperature-responsive antennas. For example, patterning twisted nematic orientation within the substrate can be used to create helical electronic devices that stretch up to 100% with less than 2% change in resistance or capacitance. Moreover, we discuss self-morphing LCE antennas which can dynamically change the operating frequency from 2.7 GHz (room temperature) to 3.3 GHz (-65 °C). We envision applications for these 3D, responsive devices in wearable or implantable electronics and in cold-chain monitoring radio frequency identification sensors. ©2019 American Chemical Society. ItemEngineering Liquid Crystalline Polymers for Biological Applications(Society for Biomaterials, 2019-04) Boothby, Jennifer M.; Ambulo, Cedric P.; Saed, M.; Ware, Taylor H.; Boothby, Jennifer M.; Ambulo, Cedric P.; Ware, Taylor H.Statement of Purpose: Large, bulky, power-hungry traditional mechanical actuators are poorly suited for small, biological applications such as medical devices. Shape changing polymers are an emerging class of actuators which can utilize environmental conditions to undergo large, complex shape changes. Liquid crystalline self-assembly is one promising strategy to program structural orientation and resulting actuation in polymeric materials. This molecular ordering can be spatially patterned, resulting in monolithic materials that undergo complex shape change. However, liquid crystal polymer networks are typically hydrophobic and only respond to stimuli that would be incompatible with biological environments, such as high temperatures and organic solvents. We have used two strategies to overcome these limitations: 1) engineering liquid crystal elastomers chemistry to respond near body temperature and 2) building gels from water-soluble, chromonic liquid crystals to respond to aqueous stimuli. ItemStereolithography of SiOC Polymer-Derived Ceramics Filled with SiC Micronwhiskers(WILEY-VCH Verlag) Brinckmann, S. A.; Patra, N.; Yao, J.; Ware, Taylor H.; Frick, C. P.; Fertig, R. S.,III; Ware, Taylor H.Due to complicated manufacturing methods and lack of machinability, the use of engineering ceramics is limited by the manufacturing processes used to fabricate parts with intricate geometries. The 3D printing of polymers that can be pyrolyzed into functional ceramics has recently been used to significantly expand the range of geometries that can be manufactured, but large shrinkage during pyrolysis has the potential to lead to cracking. In this work, a method to additively manufacture particle-reinforced ceramic matrix composites is described. Specifically, stereolithography is used to crosslink a resin comprised of acrylate and vinyl-functionalized siloxane oligomers with dispersed SiC whiskers. After crosslinking, the part is pyrolyzed to amorphous SiOC while the SiC whiskers remain unaffected. Composite ceramics shrink 37% while unreinforced parts shrink 42%; this significant reduction in shrinkage improves part stability. Importantly, these ceramic matrix composites contain no visible porosity nor cracking on the microstructural level. With the introduction of SiC, hardness increases from 10.8 to 12.1 GPa and density decreases from 2.99 to 2.86 g cm−3. Finally, printed ceramic porous structures, gears, and components for turbine blades are demonstrated. Applying stereolithographic techniques to ceramic matrix composites, this work may improve processing and properties of ceramics for applications that require complex geometries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ItemLocalized Soft Elasticity in Liquid Crystal Elastomers(Nature Pub. Group) Ware, Taylor H.; Biggins, John S.; Shick, Andreas F.; Warner, Mark; White, Timothy J.; Ware, Taylor H.Synthetic approaches to prepare designer materials that localize deformation, by combining rigidity and compliance in a single material, have been widely sought. Bottom-up approaches, such as the self-organization of liquid crystals, offer potential advantages over top-down patterning methods such as photolithographic control of crosslink density, relating to the ease of preparation and fidelity of resolution. Here, we report on the directed self-assembly of materials with spatial and hierarchical variation in mechanical anisotropy. The highly nonlinear mechanical properties of the liquid crystalline elastomers examined here enables strain to be locally reduced >15-fold without introducing compositional variation or other heterogeneities. Each domain (≥ 0.01 mm²) exhibits anisotropic nonlinear response to load based on the alignment of the molecular orientation with the loading axis. Accordingly, we design monoliths that localize deformation in uniaxial and biaxial tension, shear, bending and crack propagation, and subsequently demonstrate substrates for globally deformable yet locally stiff electronics.; ItemTopology Optimization for the Design of Folding Liquid Crystal Elastomer Actuators(Royal Society of Chemistry) Fuchi, K.; Ware, Taylor H.; Buskohl, P. R.; Reich, G. W.; Vaia, R. A.; White, T. J.; Joo, J. J.; Ware, Taylor H.Aligned liquid crystal elastomers (LCEs) are capable of undergoing large reversible shape change in response to thermal stimuli and may act as actuators for many potential applications such as self-assembly and deployment of micro devices. Recent advances in LCE patterning tools have demonstrated sub-millimetre control of director orientation, enabling the preparation of materials with arbitrarily complex director fields. However, without design tools to connect the 2D director pattern with the activated 3D shape, LCE design relies on intuition and trial and error. Here we present a design methodology to generate reliable folding in monolithic LCEs designed with topology optimization. The distributions of order/disorder and director orientations are optimized so that the remotely actuated deformation closely matches a target deformation for origami folding. The optimal design exhibits a strategy to counteract the mechanical frustration that may lead to an undesirable deformation, such as anti-clastic bending. Multi-hinge networks were developed using insights from the optimal hinge designs and were demonstrated through the fabrication and reversible actuation of a self-folding box. Topology optimization provides an important step towards leveraging the opportunities afforded by LCE patterning into functional designs.