This work defines and examines four classes of magnetorheological elastomers (MREs) based upon permutations of particle alignment-magnetization pairs. Particle alignments may either be unaligned (e.g. random) or aligned. Particle magnetizations may either be soft-magnetic or hard-magnetic. Together, these designations yield four material types: A-S, U-S, A-H, and U-H. Traditional MREs comprise only the A-S and U-S classes. Samples made from 325-mesh iron and 40 μm barium hexaferrite powders cured with or without the presence of a magnetic field served as proxies for the four classes. Cantilever bending actuating tests measuring the magnetically-induced restoring force at the cantilever tip on 50 mm × 20 mm × 5 mm samples yielded ∼350 mN at μ 0 H = 0.09 T for classes A-H, A-S, and U-S while class U-H showed only ∼40 mN. Furthermore, while classes U-S and A-S exerted forces proportional to tip deflection, they exerted no force in the undeformed state whereas class A-H exerted a relatively constant tip force over its entire range of deformation. Beam theory calculations and models with elastic strain energy density coupled with demagnetizing effects in the magnetic energy density were used to ascertain the magnitude of the internal bending moment in the cantilever and to predict material response with good results. This work highlights the ability of the newly developed A-H MRE materials, and only that material class, to operate as remotely powered bidirectional actuators.

Of special interest in the growing field of origami engineering is self-folding, wherein a material is able to fold itself in response to an applied field. In order to simulate the effect of active materials on an origami-inspired design, a dynamic model is needed. Ideally, the model would be an aid in determining how much active material is needed and where it should be placed to actuate the model to the desired position(s). A dynamic model of the origami waterbomb base, a well-known and foundational origami mechanism, is developed using adams 2014, a commercial multibody dynamics software package. Creases are approximated as torsion springs with both stiffness and damping. The stiffness of an origami crease is calculated, and the dynamic model is verified using the waterbomb. An approximation of the torque produced by magneto-active elastomers (MAEs) is calculated and is used to simulate MAE-actuated self-folding of the waterbomb. Experimental validation of the self-folding waterbomb model is performed, verifying that the dynamic model is capable of accurate simulation of the fold angles.

One of the challenges in the emerging field of origami engineering is achieving large deformations to enable significant shape transformations. Bistable compliant mechanisms provide a means to achieve this, and the goal of this research is to investigate the feasibility and design of a compliant bistable mechanism that is actuated by magneto active elastomer material. When exposed to an external field, magneto active elastomer material deforms to align embedded magnetic particles with the field. We investigate a case study using magneto active elastomer actuation through the development of finite element analysis models to predict the magnetic field required to snap the device from its first stable position to its second for various geometries and field strengths. The finite element analysis model also predicts the displacement of the mechanism as it moves from one position to the other to determine whether the device is in fact bistable. These results can be used to understand the relationship between the substrate properties and the bistability of the device. The experimental results validate the finite element analysis models and demonstrate the functionality of active magneto active elastomer materials to be used as actuators for such devices and applications of origami engineering.

The use of origami principles to create 3-dimensional shapes has the potential to revolutionize active material structures and compliant mechanisms. Active origami structures can be applied to a broad range of areas such as reconfigurable aircraft and deployable space structures as well as instruments for minimally invasive surgery. Our current research is focused on dielectric elastomer (DE) and magneto active elastomer (MAE) materials to create multi-field responsive structures. Such multi-field responsive structures will integrate the DE and MAE materials to enable active structures that fold/unfold in different ways in response to electric and/or magnetic field. They can also unfold either as a result of eliminating the applied field or in response to the application of an opposite field. This concept is demonstrated in a folding cube shape and induced locomotion in the MAE material. Two finite element models are developed for both the DE and MAE materials and validated through physical testing of these materials. The models are then integrated to demonstrate multi-field responses of a bi-fold multi-field responsive structure. The bifold model is designed to fold about one axis in an electric field and a perpendicular axis in a magnetic field. Future modeling efforts and research directions are also discussed based on these preliminary results.

Magneto-active elastomers (also called magnetorheological elastomers) are most often used in vibration attenuation application due to their ability to increase in shear modulus under a magnetic field. These shear-stiffening materials are generally comprised of soft-magnetic iron particles embedded in a rubbery elastomer matrix. More recently researchers have begun fabricating MAEs using hard-magnetic particles such as barium ferrite. Under the influence of uniform magnetic fields these hard-magnetic MAEs have shown large deformation bending behaviors resulting from magnetic torques acting on the distributed particles and consequently highlight their ability for use as remotely powered actuators. Using the magnetic-torque-driven hard-magnetic MAE materials and an unfilled silicone elastomer, this work develops novel composite geometries for actuation and locomotion. MAE materials are fabricated using 30% v/v 325 mesh barium ferrite particles in Dow Corning HS II silicone elastomers. MAE materials are cured in a 2T magnetic field to create magnetically aligned (anisotropic) materials as confirmed by vibrating sample magnetometry (VSM). Gelest optical encapsulant is used as the uniflled elastomer material. Mechanical actuation tests of cantilevers in bending and of accordion folding structures highlight the ability of the material to perform work in moderate, uniform fields of μ0H = 150 mT. Computational simulations are developed for comparison. Folding structures are also investigated as a means to produce untethered locomotion across a flat surface when subjected to an alternating field similar to scratch drive actuators; geometries investigated show promising results.