Research Areas

New origami patterns

The project is actively developing new origami patterns that are suitable for a universal electromagnetic surface.  These patterns consist of tiles that can carry active electronics, and have the ability to morph into a range of shapes.   Robert Lang has designed a new origami pattern by modifying the well-known "waterbomb" pattern.  This new pattern is characterized by tiles, and can readily morph into multiple shapes including flat, cylindrical about two axes and hemispherical.  The tiles can be designed to be active EM surfaces, and the pattern can be scaled to accommodate nxn tiles for any odd number n. 

Computational origami

We have developed computational techniques to simulate the shape transformation of origami-based mechanisms with multiple degrees of freedom and bifurcation paths. A specific problem that we have tackled is the morphing of origami mechanisms from one known configuration to another known configuration. This problem has multiple solutions, and finding the motion path that leads to the desired configuration involves a choice between the options available at each incremental step. Unilateral constraints are activated in the case of contact between different elements.  This simulation provides full kinematic information on the motion path, such as the variation of the fold angles and distances between joints, from which actuation strategies to control the shape of the origami mechanism can be developed. The geometric configurations provided by this kinematic simulation can be used for electromagnetic simulations of a active antennas built on the origami structure.

We are using this technique to conduct a full kinematic study of the new origami pattern.

Electronic origami

Electromagnetic origami is expected to be enabled by the collective response of the unit EM tiles capable of reconfiguring the field pattern along with the origamic surface actuation. Each of these unit tiles can be the size of multiple individual radiating elements and the array response in such a case is ultimately limited by the individual antenna patterns. The ultimate programmable surface is one which can synthesized on the fly at deep sub-wavelength scales. We have been able to demonstrate for the first time a new architecture that allows us to achieve this field programmability as well as frequency re-configurability at the same time. In fact, we have shown that this approach allows us to not only achieve field programmability but it break the trade-offs in classical array based designs. By dissociating a radiating surface into multiple ports for EM field synthesis and sensing, we have shown a single chip-scale programmable architecture capable of operating over 65% fractional bandwidth (35-75 GHz) with the ability to shape the beam on the fly, send multiple information across multiple directions, process multiple information from multiple directions, as well as enable spatial diversity and establish links when the main channel path is blocked. The chips are fabricated in 65 nm CMOS process and achieves close to an universal EM tile which can be tiled together for the universally programmable EM origami surface.

Bistable actuators for origami shape reconfiguration

We envision that the origami will be reconfigured into different shapes using thermally-responsive materials like shape memory alloy (SMA) and liquid crystal elastomer (LCE).  We have begun exploring ways to exploit mechanical bistability in order to maintain stable origami configurations without having to provide continuous electrical power to the actuators.  We are currently completing experimental and analytic studies on a novel bistable actuator composed of SMA wire embedded in a flexible frame that supports a stretched elastic membrane.  Electrical pulses delivered to the SMA cause the so-called "elastic minimum energy structure" to reversibly transition between stable configurations.

Objective origami

We have given a nearly complete description of all origami structures, including algorithms for constructing them, for the helical groups.  We have also made progress developing algorithms for both nondiscrete groups and the conformal groups.  We discovered a method of morphing structures by borrowing some ideas from phase transformations.  Conditions of compatibility that we have developed in our studies of phase transformations are proving to be extremely useful.  We have begun to develop algorithms that systematically can find foldable structures within a certain topological class, from a non foldable initial state.  This is a systematic method of "discovering origami".

Electronic skin with liquid metal wiring

We are developing stretchable circuits that provide electrical connectivity between origami tiles.  Because the LM circuits are highly stretchable, they can accommodate the origami's large shape changes.  This work includes novel methods to interface LM traces with rigid electronics as well as characterization of LM-embedded elastomer composites (LMEEs) in which rubber is embedded with a suspension of LM microdroplets.  When the LMEE is damaged, these droplets can rupture to form new internal conductive pathways and restore electrical functionality.  These can be tailored to display one amongst a range of electrical conductivity vs. mechanical stretch behaviors.  We have also developed a theoretical and computational model, and this shows that this electrical conductivity vs. mechanical stretch behavior depends sensitively on the microstructure explain the range of observations. 

Liquid crystal elastomers

Liquid crystal elastomers dramatically change their shape in response to actuation by heat, light or electric field.  We continue to develop a fundamental understanding of these materials.  First, in collaboration with the Tim White group in AFRL (Wright Patterson), we have proposed a general and systematic framework for the design of complex three dimensional shapes through the actuation heterogeneously patterned nematic elastomer sheets.  These sheets are composed of nonisometric origami building blocks which, when appropriately linked together, can actuate into a diverse array of three dimensional origami shapes.  Specifically, we have demonsrated that: 1) the nonisometric origami building blocks actuate in the predicted manner, 2) the integration of multiple building blocks leads to complex multi-stable, yet predictable, shapes, 3) we can bias the actuation experimentally to obtain a desired complex shape amongst the multi-stable shapes.   Second, we have proposed a model for the electrical actuation of smectic elastomer sheets in flat and curved geometries.  Finally, we are developing a detailed continuum mechanical model of the time-dependent properties of liquid crystal elastomers.