Non-linear temperature-dependent curvature of a Phase Change Composite Bimorph beam

摘要

Bimorph films curl in response to temperature. The degree of curvaturetypically varies linearly with temperature and in proportion to the differencein thermal expansion of the individual layers. In many applications, such ascontrolling a thermostat, this gentle linear behavior is acceptable. In othercases, such as opening or closing a valve or latching a deployable column intoplace, an abrupt motion at a fixed temperature is preferred. To achieve thisnon-linear motion, we describe the fabrication and performance of a new bilayerstructure we call 'Phase Change Composite Bimorph (PCBM)'. In a PCBM, one layerin the bimorph is a composite containing small inclusions of phase changematerials. When the inclusions melt, their large (generally positive and >1%)expansion coefficient induces a strong, reversible step function jump inbimorph curvature. The measured jump amplitude and thermal response isconsistent with theory.