Nonlinear deflection of a fixed–fixed hyperelastic beam under extreme stretch

We present a model that describes the deflection of a prestretched elastic beam under planar loading conditions. The kinematics is represented with a Cosserat directed curve with an extensible arc length. The strain within the cross-section of the rod is composed of bending strain and stretch of the centerline. Given that bending strains are relatively small, an effective flexural rigidity is defined based on the spatial cross-section and the slope of the hyperelastic stress–strain curve evaluated for the stretch along the neutral axis. Initially, no additional strain is assumed as the beam is deflected, and small deflections allow for the application of the small angle approximation. The solution is reduced to a fourth-order ODE that resembles an Euler–Bernoulli beam equation with a correction term accounting for axial loading. The model is further examined for the case of a stretched fixed–fixed beam under a point load applied at the center. An iterative approach is taken to accommodate further stretching as the load is applied. Experimental results are then compared to the theory. Silicone rubber beams are fixed to rigid blocks capable of shifting longitudinally to induce desired prestretches. Under various stretched conditions, the beams are then deflected vertically with a wedge while recording data on position and force. Although the Neo-Hookean constitutive model overestimates deflection at higher prestrains, a four-parameter Ogden model captures the behavior well and is in good agreement with experimental measurements for prestrains of up to 200%. The results of this analysis have applications in the area of soft robotics and electronics, where devices such as elastic microelectromechanical switches will be expected to function regardless of stretch

METHOD FOR FABRICATION OF A SOFT-MATTER PRINTED CIRCUIT BOARD

A fabrication process for soft - matter printed circuit boards is disclosed in which traces of liquid - phase Ga - In eutectic ( eGaIn ) are patterned with UV laser micromachining ( UVLM ) . The terminals of the elastomer - sealed LM circuit connect to the surface mounted chips through vertically aligned columns of eGaIn - coated ferromagnetic micro spheres that are embedded within an interfacial elastomer layer

SOFT , MULTILAYERED ELECTRONICS FOR WEARABLE DEVICES AND METHODS TO PRODUCE THE SAME

Disclosed herein is an efficient fabrication approach to create highly customizable wearable electronics through rapid laser machining and adhesion - controlled soft materials assembly . Well - aligned , multi - layered materials can be created from 2D and 3D elements that stretch and bend while seamlessly integrating with rigid components such as micro chip integrated circuits ( IC ) , discrete electrical components , and interconnects . These techniques are applied using commercially available materials . These materials and methods enable custom wearable electronics while offering versatility in design and functionality for a variety of bio - monitor ing applications

Modeling of curved cantilever dielectric elastomer actuator using universal solution in finite bending

This study presents a model of a curved cantilever dielectric elastomer actuator (DEA) containing liquid-phase metal electrodes utilizing universal solutions from finite nonlinear elasticity. The DEA comprises a compliant capacitor which has been prestrained some prescribed amount, affixed to a substrate, and bonded to a secondary layer of unstrained bulk elastomer. Upon release of the cured layers, internal stresses cause a bending moment and force the final configuration into a beam with some initial curvature. Application of a voltage across the electrodes creates an electrostatic pressure, inducing compressive Maxwell stresses across the dielectric layer. This relieves some of the internal moment and forces actuation of the device in the form of beam straightening. We assume incompressibility and isotropic, neo-Hookean behavior of our bulk elastomeric material. Employing simplifying assumptions such as constant curvature across the length of the beam (i.e., a perfectly circular arc) and plane strain in the plane of actuation, we utilize the Universal Solution in finite bending to represent the kinematics and implement Maxwell’s equations to describe beam deflection as a function of applied voltage. We use the principal of minimum potential energy to solve for beam deflection (represented by curvature of the device) as a function of electric potential across the electrodes after considering energy contributions due to elasticity, electrostatics and expended electric work. This model is then compared to experimental data obtained from testing multiple fabricated devices. The emerging fields of soft robotics and wearable computing require new classes of soft and elastically deformable electronics, which unlike traditional electronic components, must be flexible and/or stretchable. Thus it is important to develop predictive and comprehensive models describing their behavior

Soft-matter damage detection systems for electronics and structures

Soft-matter technologies are essential for emerging applications in wearable computing, human-machine interaction, and soft robotics. However, as these technologies gain adoption in society and interact with unstructured environments, material and structure damage becomes inevitable. Here, we present a robotic material that mimics soft tissues found in biological systems to identify, compute, and respond to damage. This system is composed of liquid metal droplets dispersed in soft elastomers that rupture when damaged, creating electrically conductive pathways that are identified with a soft active-matrix grid. This presents new opportunities to autonomously identify damage, calculate severity, and respond to prevent failure within robotic systems

Safe Supervisory Control of Soft Robot Actuators

Although soft robots show safer interactions with their environment than traditional robots, soft mechanisms and actuators still have significant potential for damage or degradation particularly during unmodeled contact. This article introduces a feedback strategy for safe soft actuator operation during control of a soft robot. To do so, a supervisory controller monitors actuator state and dynamically saturates control inputs to avoid conditions that could lead to physical damage. We prove that, under certain conditions, the supervisory controller is stable and verifiably safe. We then demonstrate completely onboard operation of the supervisory controller using a soft thermally-actuated robot limb with embedded shape memory alloy (SMA) actuators and sensing. Tests performed with the supervisor verify its theoretical properties and show stabilization of the robot limb's pose in free space. Finally, experiments show that our approach prevents overheating during contact (including environmental constraints and human contact) or when infeasible motions are commanded. This supervisory controller, and its ability to be executed with completely onboard sensing, has the potential to make soft robot actuators reliable enough for practical use

All the Feels: A dexterous hand with large area sensing

High cost and lack of reliability has precluded the widespread adoption of dexterous hands in robotics. Furthermore, the lack of a viable tactile sensor capable of sensing over the entire area of the hand impedes the rich, low-level feedback that would improve learning of dexterous manipulation skills. This paper introduces an inexpensive, modular, robust, and scalable platform - the DManus- aimed at resolving these challenges while satisfying the large-scale data collection capabilities demanded by deep robot learning paradigms. Studies on human manipulation point to the criticality of low-level tactile feedback in performing everyday dexterous tasks. The DManus comes with ReSkin sensing on the entire surface of the palm as well as the fingertips. We demonstrate effectiveness of the fully integrated system in a tactile aware task - bin picking and sorting. Code, documentation, design files, detailed assembly instructions, trained models, task videos, and all supplementary materials required to recreate the setup can be found on http://roboticsbenchmarks.org/platforms/dmanusComment: 6 pages + references and appendix, 7 figures. Submitted to ICRA 202

Influence of cross-sectional geometry on the sensitivity and hysteresis of liquidphase electronic pressure sensors

Differential reflectance modulation sensing with diffractive microstructures Appl. Phys. Lett. 101, 191103 (2012) Silicon nanowire based Pirani sensor for vacuum measurements Appl. Phys. Lett. 101, 183506 (2012) Note: Position self-sensing for piezoelectric actuators in the presence of creep and rate-dependent hysteresis Rev. Sci. Instrum. 83, 116101 (2012) Dynamic photoacoustic spectroscopy for trace gas detectio