jamSheets – Thin Interfaces with Tunable Stiffness

Research @ MIT Media Lab | 2013-2015

 

This works introduces layer jamming as an enabling technology for designing deformable, stiffness-tunable, thin sheet interfaces. Interfaces that exhibit tunable stiffness properties can yield dynamic haptic feedback and shape deformation capabilities. In comparison to the particle jamming, layer jamming allows for constructing thin and lightweight form factors of an interface. We propose five layer structure designs and an approach which composites multiple materials to control the deformability of the interfaces. We also present methods to embed different types of sensing and pneumatic actuation layers on the layer-jamming unit. Through three application prototypes we demonstrate the benefits of using layer jamming in interface design. Finally, we provide a survey of materials that have proven successful for layer jamming.

Publication | TEI2014 | jamSheets: Thin Interfaces with Tunable Stiffness Enabled by Layer Jamming | Ou, J., Yao, L., Tauber, D., Steimle, J., Niiyama, R., Ishii, H.

Mechanism | Layer-jamming systems can be composed of an airtight envelope with multiple thin layers of “flaps” (e.g., paper) inside. As with particle jamming, the system utilizes negative air pressure to vacuum-pack the thin layers of material to amplify the friction between each layer. The maximum resisting tensile force (F) can be calculated as follows: F = µnPS, where S, P, n and µ represent the overlapped surface area, the pressure applied on the surface, the number of layers present, and friction coefficient of the thin layers respectively.

Stiffness-changing Display | In this application, we introduce tunable stiffness as a physical parameter in displaying digital contents. The first scenario demonstrates that the display can simulate stiffness of different projected material textures. We sequentially project three material textures (wood, foam and leather) on a layer-jamming unit, which is shaped like a tablet. When the visually projected texture changes, the layer-jamming control system provides negative or positive air pressure to adjust the display’s stiffness; the wood is the stiffest material and leather is the most flexible one.

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Deformable Furniture | We design a portable chair that resembles a flat, flexible carpet in its unjammed state, such that it can be folded and carried easily. When users transform the flat sheet into the shape of a chair by creating two folds where the sensors are embedded, the system will automatically start the jamming process after three seconds. Once jammed, the carpet will become stiff enough to maintain the chair shape and support up to a load of up to 55 kilograms. The carpet can be formed into other 3D shapes as well, such as a table board, or a free-formed lounge.

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Pneumatic Control System | In a layer-jamming control system, air can be either vacuumed out of or pumped into the jamming envelope. A layer-jamming control circuit can be composed of two 3-port solenoid valves and one air pump for a single jamming envelope. For most of our tests and applications, we built a portable control system composed of an Arduino mini Pro, mini Arduino FET shield, SMC s070c-sdg-32 solenoid valves and AIRPO mini D2028 air pump. There are three modes to control the airflow in and out of the layer-jamming envelope: exhaust, supply, and close. The exhaust/supply is the mode to deflate/inflate an air bag, respectively. The close mode stops the airflow to maintain the system at a certain air pressure and therefore a degree of stiffness.

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Material Test | Based on the aforementioned calculation of layer jamming’s maximum resistance to tensile loads, stacking layer materials with high friction coefficients can achieve a higher stiffness while the system is jammed. However, some materials, which have high friction coefficients, cannot achieve a considerable stiffness when jammed due to their own softness. Therefore the material selection is not trivial anymore. For this paper, we have surveyed 32 types of thin sheet materials that are that are relatively inexpensive, commercially available materials, and conducted bending torque comparison tests between normal and jammed states to quantify a material’s stiffness change. The purpose of this test is to provide designers and researchers with an overview of what materials are suitable for layer jamming and to compare and extrapolate relevant and desirable properties (thickness and weight) for different applications.

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