A polymer strand that contracts when exposed to light and expands when the light source is removed
The U.S. Navy seeks to commercialize U.S. Patents 6,669,442 and 6,776,971 (both titled “Visible light pH change for activating polymers and other pH dependent reactants”).
A number of natural and synthetic fibers and gels expand and contract when exposed to an environmental change, such as a change in solvent composition, temperature, pH, electric field or photo irradiation. As a commercially exploitable technology, the fibers and gels have applications in many fields, such as use in sensors, switches, motors, pumps, and non-metallic operations, as well as use in the medical and robotic fields where it is envisioned that these materials will be able to carry out the function of human muscle tissue. With current technology, contraction times are extremely short (10 nanoseconds), the light used is UV and causes damage to the solution, and heat buildup is discharged too slowly for a quick return of the compound to its natural resting state. SSC Pacific has created a technology that overcomes these deficiencies.
With a bit of light and a simple solution of polymers, SSC Pacific has created a new and novel way to induce mechanical motion in the form of contraction and expansion, and has patents on the apparatus for doing so. When exposed to visible light, the solution’s pH balance changes and the polymer reacts by contracting. The polymer can maintain the contraction indefinitely, discharging heat from the light so that once the light is removed, the solution can return to its original state in milliseconds. Thus an expandable and contractible polymer solution can be made to respond rapidly to a change in pH while the heat-release mechanism of the invention allows the polymer to return to its initial configuration in milliseconds.
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- SD 691, April 2007. SSC Pacific, San Diego, CA 92152–5001. Approved for public release; distribution is unlimited.