Three-dimensional blueprinting of molecular patterns in liquid crystalline polymers.

Exploiting the interplay of anisotropic diamagnetic susceptibility of liquid crystalline monomers and site selective photopolymerization enables the fabrication of 3D freeforms with highly refined microstructures. Utilizing chain transfer agents in the mesogenic inks presents a pathway for broadly tuning the mechanical properties of liquid crystalline polymers and their response to stimuli. In particular, the combination of 1,4-benzenedimethanethiol and tetrabromomethane is shown to enable voxelated blueprinting of molecular order, while allowing for a modulation of the crosslink density and the mechanical properties. The formulation of these monomers allows for the resolution of the voxels to approach the limits set by the coherence lengths defined by the anchoring from surfaces. These compositions demonstrate the expected thermotropic responses while allowing for their functionalization with photochromic switches to elicit photomechanical responses. Actuation strains are shown to outstrip that accomplished with prior systems that did not access chain transfer agents to modulate the structure of the macromolecular network. Test cases of this system are shown to create freeform actuators that exploit the refined director patterns during high-resolution printing. These include topological defects, hierarchically-structured light responsive grippers, and biomimetic flyers whose flight dynamics can be actively modulated via irradiation with light.

Thermomechanically active electrodes power work-dense soft actuators.

The effect of chain extender structure and composition on the thermomechanical properties of liquid crystal elastomers (LCE) synthesized using thiol-acrylate Michael addition is presented. The intrinsic molecular stiffness of the thiol chain extender and its relative molar ratio to acrylate-based host mesogens determine the magnitudes of the thermomechanical strains, temperatures at which they are realized and the mechanical work-content. A non-linear structure-property relationship emerges, wherein higher concentrations of flexible extenders first magnify the thermomechanical sensitivity, but a continued increase leads to weaker actuation. Understanding this interplay leads to a composite material platform, enabling a peak specific work production of ∼2 J kg-1 using ∼115 mW of electrical power supplied at 2 V. Composites of LCE with eGaIn liquid metal (LM) are prepared, which act as heaters, while being capable of actuation themselves. The thermomechanically active electrodes convert the electrical power into Joule heat, which they efficiently couple with the neat LCE to which they are bound. This system harnesses the nascent responsiveness of the LCE using electrodes that work with them, instead of fighting against them (or passively standing in the way). Specific work generated increases when subjected to increasing levels of load, reaching a peak at loads ∼260× the actuator weight. These ideas are extended to tri-layered actuators, where LCE films with orthogonal molecular orientations sandwich LCE-LM composite heaters. Torsional actuation modes are harnessed to twist under load.

Voxelated Molecular Patterning in Three-Dimensional Freeforms.

The ability to pattern material response, voxel by voxel, to direct actuation and manipulation in macroscopic structures can enable devices that utilize ambient stimuli to produce functional responses at length scales ranging from the micro- to the macroscopic. Fabricating liquid crystalline polymers (LCPs), where the molecular director is indexably defined in three-dimensional (3D) freeforms, can be a key enabler. Here, the combination of anisotropic magnetic susceptibility of the liquid crystalline monomers in a reorientable magnetic field and spatially selective photopolymerization using a digital micromirror device to independently define molecular orientation in light and/or heat-responsive multimaterial elements, which are additively incorporated into 3D freeforms, is exploited. This is shown to enable structural complexity across length scales in nontrivial geometries, including re-entrant shapes, which are responsive to either heat or light. A range of monomer compositions are optimized to include photoinitiators, light absorbers, and polymerization inhibitors to modulate the polymerization characteristics while simultaneously retaining the tailorability of the nematic alignment. The versatility of this framework is illustrated in an array of examples, including (i) thermomechanical generation of Gaussian-curved structures from flat geometries, (ii) light-responsive freeform topographies, and (iii) multiresponsive manipulators, which can be powered along independent axes using heat and/or light. The ability to integrate responses to multiple stimuli, where the principal directions of the mechanical output are arbitrarily tailored in a 3D freeform, enables new design spaces in soft robotics, micromechanical/fluidic systems, and optomechanical systems.

Synchronous adrenocortical neoplasms, paragangliomas, and pheochromocytomas: syndromic considerations regarding an unusual constellation of endocrine tumors.

The most common clinical syndromes presenting with paragangliomas and/or pheochromocytomas as their endocrine components are multiple endocrine neoplasia type 2, neurofibromatosis, Von Hippel-Lindau syndrome, Carney-Stratakis syndrome, Carney triad, and the recently described hereditary paraganglioma syndrome. Only Carney triad is known to also present with adrenocortical adenomas, currently representing the only described syndrome in which all 3 of the aforementioned tumors are found together. In most cases, prototypical lesions of the triad such as gastrointestinal stromal tumor and pulmonary chondromas are also seen. We present a case of a young woman with synchronous paragangliomas, adrenal/extra-adrenal cortical neoplasms, and pheochromocytoma without genetic mutations for multiple endocrine neoplasia 2, Von Hippel-Lindau syndrome, neurofibromatosis, and succinate dehydrogenase. We speculate that this represents a previously undescribed presentation of Carney triad and, at the very least, indicates the need for monitoring for the development of other tumors of the triad.