Abstract
An electrothermal microgripper is an important actuator in microelectromechanical and micro-operating systems, and its temperature field analysis is the core problem in research and design. Because of the small size of an electrothermal microgripper, its microscale heat transfer characteristics are different from those of the macrostate. At present, only a few studies on the heat transfer scale effect in electrothermal microgrippers have been conducted, and the heat transfer analysis method under the macrostate is often used directly. The temperature field analysed and simulated is different from the actual situation. In the present study, the heat transfer mechanism of an electrothermal microgripper in the microscale was analysed. The temperature field of a series of microscale heating devices was measured using microthermal imaging equipment, and the heat transfer parameters of the microscale were fitted. Results show that the natural convective heat transfer coefficient of air on the microscale can reach 60–300 times that on the macroscale, which is an important heat transfer mode affecting the temperature field distribution of the electrothermal microgripper. Combined with the finite element simulation software, the temperature field of the electrothermal microgripper could be accurately simulated using the experimental microscale heat transfer parameters measured. This study provides an important theoretical basis and data support for the optimal design of the temperature controller of the electrothermal microgripper.
Highlights
As a typical actuator of a microelectromechanical system (MEMS), a microgripper is mainly used to perform operations such as gripping, moving and assembling several small objects, and it plays a vital role in the implementation of the micro-operation process [1,2,3,4,5]
These formulas indicate an exponential relationship between the convective heat transfer coefficient and the range of the feature size scale, which has a significant influence on the heat transfer characteristics of the electrothermal microgripper
Heat transfer parameters measured in the heat experiment match the actual heat transfer law of the electrothermal microgripper, the measured heat transfer parameters and the heat transfer macroparameters are substituted into the electrothermal parallel-beam microgripper, and the temperature distribution obtained is compared with the measured temperature field
Summary
As a typical actuator of a microelectromechanical system (MEMS), a microgripper is mainly used to perform operations such as gripping, moving and assembling several small objects, and it plays a vital role in the implementation of the micro-operation process [1,2,3,4,5]. Microgrippers are mainly classified as piezoelectric, electromagnetic, pneumatic, electrostatic and electrothermal according to the drive mode. Among these types, the electrothermal microgripper has attracted considerable attention owing to its advantages such as simple structure, small volume, fast response, positive driving force, strong antiinterference capability and easy control [6,7]. Only a few studies on the heat transfer scale effect in electrothermal microgrippers have been conducted. Nath and Chopra [13] determined that, from 6000 Å to 400 Å, the heat conductivity of copper decreases by five times These studies propose that the heat transfer characteristics do have a scale effect and no consensus has been reached on the heat transfer parameters. The matching degree between the heat transfer parameters and the actual heat transfer characteristics of the electrothermal microgripper was verified by experimental comparison
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