Thermo-Mechanical Fluid–Structure Interaction Numerical Modelling and Experimental Validation of MEMS Electrothermal Actuators for Aqueous Biomedical Applications

Abstract

Recent developments in MEMS technologies have made such devices attractive for use in applications that involve precision engineering and scalability. In the biomedical industry, MEMS devices have gained popularity in recent years for use as single-cell manipulation and characterisation tools. A niche application is the mechanical characterisation of single human red blood cells, which may exhibit certain pathological conditions that impart biomarkers of quantifiable magnitude that are potentially detectable via MEMS devices. Such applications come with stringent thermal and structural specifications wherein the potential device candidates must be able to function with no exceptions. This work presents a state-of-the-art numerical modelling methodology that is capable of accurately predicting MEMS device performance in various media, including aqueous ones. The method is strongly coupled in nature, whereby thermal as well as structural degrees of freedom are transferred to and from finite element and finite volume solvers at every iteration. This method therefore provides MEMS design engineers with a reliable tool that can be used in design and development stages and helps to avoid total reliability on experimental testing. The proposed numerical model is validated via a series of physical experiments. Four MEMS electrothermal actuators with cascaded V-shaped drivers are presented. With the use of the newly proposed numerical model as well as the experimental testing, the MEMS devices’ suitability for biomedical applications is confirmed.

Actuation for flexible and stretchable microdevices

“…SOIMUMPs™ was used to fabricate bent-beam actuators. 42,103 Moreover, SOIMUMPs™ allows for making multiple devices on a single silicon wafer. Thermal expansion-based actuators and phase change actuators, such as SMA-based thin film microactuators, can be fabricated by micromachining processes such as low-pressure chemical vapour deposition, sputtering, wet etching, and reactive ion etching that involve photolithography in these subsequent steps.…”

“…For instance, Dai et al 101 chose 1 0 inclination angles for the designed bent-beam actuator and achieved 80.75 μm in-plane displacement with a 4 V input voltage. The configurations of bent-beam actuators include beam-array, 102 cascaded bent-beam, 103 Z-shape beam, 100 and out-of-plane bent-beam. 104 Moreover, bent-beam type actuators can be improved by carefully selecting the number of beams to provide higher displacements while improving the mechanical performance.…”

“…104 Moreover, bent-beam type actuators can be improved by carefully selecting the number of beams to provide higher displacements while improving the mechanical performance. 103 The main reason for the improved performance is the close arrangement of beams that isolate the actuator from its surroundings, resulting in a higher operating temperature. The bent-beam actuator configuration is more robust than other electro-thermal actuators.…”