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

TL;DR

This paper introduces a novel phase change composite bimorph (PCBM) that exhibits a non-linear, step-function curvature change with temperature, enabling abrupt motion control in various applications.

Contribution

The paper presents the design, fabrication, and performance analysis of a new bilayer structure with phase change inclusions that produce non-linear curvature behavior.

Findings

The PCBM shows a reversible step change in curvature at the phase change temperature.

The experimental results match theoretical predictions.

The structure enables abrupt motion control in thermal applications.

Abstract

Bimorph films curl in response to temperature. The degree of curvature typically varies linearly with temperature and in proportion to the difference in thermal expansion of the individual layers. In many applications, such as controlling a thermostat, this gentle linear behavior is acceptable. In other cases, such as opening or closing a valve or latching a deployable column into place, an abrupt motion at a fixed temperature is preferred. To achieve this non-linear motion, we describe the fabrication and performance of a new bilayer structure we call 'Phase Change Composite Bimorph (PCBM)'. In a PCBM, one layer in the bimorph is a composite containing small inclusions of phase change materials. When the inclusions melt, their large (generally positive and >1%) expansion coefficient induces a strong, reversible step function jump in bimorph curvature. The measured jump amplitude and thermal response is consistent with theory.