Rotational multimaterial printing of filaments with subvoxel control.

Helical structures are ubiquitous in nature and impart unique mechanical properties and multifunctionality. So far, synthetic architectures that mimic these natural systems have been fabricated by winding, twisting and braiding of individual filaments, microfluidics, self-shaping and printing methods. However, those fabrication methods are unable to simultaneously create and pattern multimaterial, helically architected filaments with subvoxel control in arbitrary two-dimensional (2D) and three-dimensional (3D) motifs from a broad range of materials.

Optically addressable dielectric elastomer actuator arrays using embedded percolative networks of zinc oxide nanowires.

Dielectric elastomer actuators (DEAs) are electrically driven soft actuators that generate fast and reversible deformations, enabling lightweight actuation of many novel soft robots and haptic devices. However, the high-voltage operation of DEAs combined with the paucity of soft, small high-voltage microelectronics has limited the number of discrete DEAs that can be incorporated into soft robots. This has hindered the versatility as well as complexity of the tasks that they can perform which, in practice, depends on the number of independently addressable actuating elements.

Programmed shape-morphing into complex target shapes using architected dielectric elastomer actuators.

Dielectric elastomer actuators (DEAs) are among the fastest and most energy-efficient, shape-morphing materials. To date, their shapes have been controlled using patterned electrodes or stiffening elements. While their actuated shapes can be analyzed for prescribed configurations of electrodes or stiffening elements (the forward problem), the design of DEAs that morph into target shapes (the inverse problem) has not been fully addressed.

A Wearable Textile-Embedded Dielectric Elastomer Actuator Haptic Display.

With advances in mobile computing and virtual/augmented reality technologies, communicating through touch using wearable haptic devices is poised to enrich and augment current information delivery channels that typically rely on sight and hearing. To realize a wearable haptic device capable of effective data communication, both ergonomics and haptic performance (i.e.

Voltage-tunable elastomer composites that use shape instabilities for rapid structural color changes.

Structurally colored materials can switch colors in response to external stimuli, which makes them potentially useful as colorimetric sensors, dynamic displays, and camouflage. However, their applications are limited by the angular dependence, slow response, and absence of synchronous control in time and space. In addition, out-of-plane deformation from shape instability easily occurs in photonic films, leading to inhomogeneous colors in photonic-crystal materials.

Photoswitchable Covalent Adaptive Networks Based on Thiol-Ene Elastomers.

Covalent adaptive networks combine the advantages of cross-linked elastomers and dynamic bonding in a single system. In this work, we demonstrate a simple one-pot method to prepare thiol-ene elastomers that exhibit reversible photoinduced switching from an elastomeric gel to fluid state. This behavior can be generalized to thiol-ene cross-linked elastomers composed of different backbone chemistries (e.

A Wearable Soft Haptic Communicator Based on Dielectric Elastomer Actuators.

Dielectric elastomer actuators exhibit an unusual combination of large displacements, moderate bandwidth, low power consumption, and mechanical impedance comparable with human skin, making them attractive for haptic devices. In this article, we propose a wearable haptic communication device based on a two-by-two array of dielectric elastomer linear actuators. We briefly describe the architecture of the actuators and their mechanical and electrical integration into a wearable armband.

Controlled flight of a microrobot powered by soft artificial muscles.

Flying insects capable of navigating in highly cluttered natural environments can withstand in-flight collisions because of the combination of their low inertia and the resilience of their wings, exoskeletons and muscles. Current insect-scale (less than ten centimetres long and weighing less than five grams) aerial robots use rigid microscale actuators, which are typically fragile under external impact. Biomimetic artificial muscles that are capable of large deformation offer a promising alternative for actuation because they can endure the stresses caused by such impacts.

Ten Years of Data Verification: The Society of Thoracic Surgeons Congenital Heart Surgery Database Audits.

Background: The completeness and accuracy of data contained within clinical databases and registries is critical to the reliability of reports emanating from these platforms. Therefore, vigorous data verification processes are a core competency of any mature database or registry. The Society of Thoracic Surgeons Congenital Heart Surgery Database (STS CHSD) has conducted audits of participant data for just over ten years.

Realizing the potential of dielectric elastomer artificial muscles.

Soft robotics represents a new set of technologies aimed at operating in natural environments and near the human body. To interact with their environment, soft robots require artificial muscles to actuate movement. These artificial muscles need to be as strong, fast, and robust as their natural counterparts.

Reconfigurable shape-morphing dielectric elastomers using spatially varying electric fields.

Exceptionally large strains can be produced in soft elastomers by the application of an electric field and the strains can be exploited for a variety of novel actuators, such as tunable lenses and tactile actuators. However, shape morphing with dielectric elastomers has not been possible since no generalizable method for changing their Gaussian curvature has been devised. Here it is shown that this fundamental limitation can be lifted by introducing internal, spatially varying electric fields through a layer-by-layer fabrication method incorporating shaped, carbon-nanotubes-based electrodes between thin elastomer sheets.

Adaptive metalenses with simultaneous electrical control of focal length, astigmatism, and shift.

Focal adjustment and zooming are universal features of cameras and advanced optical systems. Such tuning is usually performed longitudinally along the optical axis by mechanical or electrical control of focal length. However, the recent advent of ultrathin planar lenses based on metasurfaces (metalenses), which opens the door to future drastic miniaturization of mobile devices such as cell phones and wearable displays, mandates fundamentally different forms of tuning based on lateral motion rather than longitudinal motion.

Large area metalenses: design, characterization, and mass manufacturing.

Optical components, such as lenses, have traditionally been made in the bulk form by shaping glass or other transparent materials. Recent advances in metasurfaces provide a new basis for recasting optical components into thin, planar elements, having similar or better performance using arrays of subwavelength-spaced optical phase-shifters. The technology required to mass produce them dates back to the mid-1990s, when the feature sizes of semiconductor manufacturing became considerably denser than the wavelength of light, advancing in stride with Moore's law.

Multilayer Dielectric Elastomers for Fast, Programmable Actuation without Prestretch.

A novel method for the fabrication of dielectric elastomer actuators (DEAs) combines acrylic polymers and single wall carbon nanotube network electrodes. DEAs made using this technique do not require prestretching, have extremely thin electrodes, and can be actuated at low voltage. The method is applied to create a multimorph device with nine actuation modes based on just four inputs.

Pattern formation in plastic liquid films on elastomers by ratcheting.

Plastic liquids, also known as Bingham liquids, retain their shape when loads are small, but flow when loads exceed a threshold. We discovered that plastic liquid films coated on elastomers develop wavy patterns under cyclic loads. As the number of cycles increases, the wavelength of the patterns remains unchanged, but the amplitude of the patterns increases and then saturates.

Electrically tunable window device.

A device for controlling the transmittance of light over large areas, such as windows, is described. It is based on electrostatically induced surface deformation of soft dielectric elastomer sheets produced when a voltage is applied between two networks of electrically conducting nanowires on either side of the elastomer. Variations in the surface curvature are produced by the applied voltage refract light, decreasing the optical transmittance at all wavelengths.

Electrically-tunable surface deformation of a soft elastomer.

The flat surface of a thin elastomer on a conducting substrate can be deformed by applying an electric field to a percolating network of metallic nanowires randomly dispersed over the surface. The magnitude of the field-induced surface undulations increases with the applied field and can locally be several times the diameter of the nanowires. Optical imaging indicates that the effect is reversible and the surface flatness is recovered when the electric field is removed.

Dielectric Elastomer Based "Grippers" for Soft Robotics.

The use of few stiff fibers to control the deformation of dielectric elastomer actuators, in particular to break the symmetry of equi-biaxial lateral strain in the absence of prestretch, is demonstrated. Actuators with patterned fibers are shown to evolve into unique shapes upon electrical actuation, enabling novel designs of gripping actuators for soft robotics.

Optimizing the electrical energy conversion cycle of dielectric elastomer generators.

A strategy to control the electrical charge is developed to achieve high energy density of soft dielectric elastomer generators for energy harvesting. The strategy is analytically shown and experimentally demonstrated to produce the highest energy density ever reported for a soft generator.

Effect of silane coupling agent chemistry on electrical breakdown across hybrid organic-inorganic insulating films.

Dielectric breakdown measurements were conducted on self-assembled monolayer (SAM)/native silicon oxide hybrid dielectrics using conductive atomic force microscopy (C-AFM). By depositing silane coupling agents (SCAs) through a diffusional barrier layer, SAM roughness was decoupled from chemistry to compare the chemical effects of exposed R-group functionality on dielectric breakdown. Using Weibull and current-voltage (I-V) analysis, the breakdown strength was observed to be independent of SCA R-group length, and the addition of a SAM was seen to improve the breakdown strength relative to native silicon oxide by up to 158%.

Structural transition from helices to hemihelices.

Helices are amongst the most common structures in nature and in some cases, such as tethered plant tendrils, a more complex but related shape, the hemihelix forms. In its simplest form it consists of two helices of opposite chirality joined by a perversion. A recent, simple experiment using elastomer strips reveals that hemihelices with multiple reversals of chirality can also occur, a richness not anticipated by existing analyses.

Complex ordered patterns in mechanical instability induced geometrically frustrated triangular cellular structures.

Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures.

Report from the Society of Thoracic Surgeons National Database Workforce: clarifying the definition of operative mortality.

Several distinct definitions of postoperative death have been used in various quality reporting programs. Some have defined postoperative mortality as the occurrence of death after a surgical procedure when the patient dies while still in the hospital, while others have considered all deaths occurring within a predetermined, standardized time interval after surgery to be postoperative mortality. While mortality data are still collected and reported using both these individual definitions, the Society of Thoracic Surgeons (STS) believes that either approach alone may be inadequate.

Tunable lenses using transparent dielectric elastomer actuators.

Focus tunable, adaptive lenses provide several advantages over traditional lens assemblies in terms of compactness, cost, efficiency, and flexibility. To further improve the simplicity and compact nature of adaptive lenses, we present an elastomer-liquid lens system which makes use of an inline, transparent electroactive polymer actuator. The lens requires only a minimal number of components: a frame, a passive membrane, a dielectric elastomer actuator membrane, and a clear liquid.