High Energy Density Nastic Structures Using Biological Transport Mechanisms
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Published: 2007
Total Pages: 33
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DOWNLOAD EBOOKA new mechanical actuation concept is demonstrated based on the controlled transport of fluid across semi-permeable membranes. This concept is based on the pressurization of cells similar to the process that plants use to maintain homeostasis and regulate cell function. In all plant systems, the transport of ions and fluid produce localized pressure changes (called turgor pressure) that perform many cell functions, such as maintaining cell integrity and controlling plant growth. In this article, we demonstrate that the concept of fluid transport caused by protein transporters can be used to control the actuation properties of a mesoscale device. The device considered in this work consists of two chambers separated by a semi-permeable membrane substrate that contains protein transporters suspended in a lipid bilayer. The protein transporters convert biochemical energy in the form of ATP into a protein gradient across the semipermeable membrane. The proton gradient, in turn, induces a flow of fluid across the porous substrate and pressurizes a closed volume. The experimental demonstration uses a directly applied gradient. The pressurization of the closed volume produces a deformation in the cover plate of the chamber, thus transforming the chemical energy of the ATP into a measurable motion in the actuator. Experiments on the device demonstrate that micron-scale displacements can be induced in a millimeter-scale actuator. The time constant of the response is on the order of tens of seconds, and results demonstrate that the pH gradient (or) amount of ATP and ATPase control the actuation properties of the device. To our knowledge, this is the first demonstration of using natural protein transporters as the active component of a mechanical actuator.
