Jinxiong Zhou's blog

The synergic combination of smart soft composites with kirigami/origami principles leads to self-deployable systems. To date, the development of soft deployable structures has largely been an empirical process. Focusing on the recently developed shape memory alloy (SMA)-based soft deployable structures, this paper describes an analytical model and a finite element (FE) numerical scheme to investigate deformation and deployment performance of this system.

We combine experiment and finite element simulation and come up with a design of a mechanical metamaterial which demonstrates snap-back induced hysteresis and energy dissipation. The resultant is an elastic system that can be used reversibly for many times. The underlying mechanism of existence of hysteresis and the physics of snap-back induced elastic instability is unveiled. Our results open an avenue for design and implementation of recoverable energy dissipation devices by harnessing mechanical instability.

A majority of dielectric elastomers (DE) developed so far have more or less viscoelastic properties. Understanding the dynamic behaviors of DE is crucial for devices where inertial effects can not be neglected. Through construction of a dissipation function, we applied the Lagrange’s method and theory of non-equilibrium thermodynamics of DE and formulated a physics-based approach for dynamics of viscoelastic DE. We revisited the nonlinear oscillation of DE balloons and proposed a combined shooting and arc-length continuation method to solve the highly nonlinear equations.

Imitating origami principles in active or programmable materials opens the door for development
of origami-inspired self-folding structures for not only aesthetic but also functional purposes. A
variety of programmable materials enabled self-folding structures have been demonstrated across
various fields and scales. These folding structures have finite thickness and the mechanical
properties of the active materials dictate the folding process. Yet formalizing the use of origami
rules for use in computer modeling has been challenging, owing to the zero-thickness theory and

A cantilever beam with elastic hinge pulled antagonistically by two dielectric elastomer (DE) membranes in tension forms a foldable actuator if one DE membrane is subject to a voltage and releases part of tension. Simply placing parallel rigid bars on the prestressed DE membranes results in enhanced actuators working in pure shear state. We report design, analysis, fabrication and experiment of soft mobile robots that are moved by such foldable DE actuators.

Combining
soft active hydrogels with hard passive polymers gives rise to all-polymer
composites. The hydrogel is sensitive to external stimuli while the passive
polymer is inert. Utilizing the different behaviors of two materials subject to
environmental variation, for example temperature, results in self-folding soft
machines. We report our efforts to model the programmable deformation of
self-folding structures with temperature-sensitive hydrogels. The self-folding
structures are realized either by constructing a bilayer structure or by
incorporating hydrogels as hinges. The methodology and the results may aid the

When an electric voltage is applied across the thickness of a thin layer of an dielectric elastomer, the layer reduces its thickness and expands its area. This electrically induced deformation can be rapid and large, and is potentially useful as soft actuators in diverse technologies. Recent experimental and theoretical studies have shown that, when the voltage exceeds some critical value, the homogenous deformation of the layer becomes unstable, and the layer deforms into a mixture of thin and thick regions.

A subdomain collocation method based on Voronoi diagrams and reproducing kernel approximation is presented. The unkonwn field variables are approximated via reproducing kernel approximation. The body integration arising from the numerical evaluation of Galerkin weak form is converted into much cheaper contour integration along the boundary of each Voronoi cell. The Voronoi cells also provide an natural structure to perform h-adaptivity.