SU-8 Electrothermal Actuators: Optimization of Fabrication and Excitation for Long-Term Use

Micromachines

Thomas Winterstein¹  Matthias Staab¹  Christian Nakic¹  Hans-Jürgen Feige²  Jürgen Vogel²  Helmut F. Schlaak¹ 

[1] Microtechnology and Electromechanical Systems Laboratory, Institute of Electromechanical Design, Technische Universität Darmstadt, Merckstr. 25, 64283 Darmstadt, Germany; E-Mails:;Laboratory of Experimental Solid and Micro Mechanics, Faculty of Automotive Engineering, Westsächsische Hochschule Zwickau, Dr.-Friedrichs-Ring 2A, 08056 Zwickau, Germany; E-Mails:

关键词: electrothermal actuator;    SU-8;    long-term stability;    pseudo-bimorph;    glass transition temperature;   

DOI  :  10.3390/mi5041310

来源: mdpi

【 摘 要 】

In this paper we examine the suitability of SU-8 2000 as a construction material for electrothermal actuators and the actuator stability for long-term operation. The fabrication of SU-8 was optimized for mechanical and thermal stability. Samples with different softbake duration, exposure dose and postbake temperature were evaluated using Fourier-Transform IR-spectroscopy and dynamic-mechanical analysis. The exposure dose and postbake temperature proved to have a strong influence on the cross-linking and the glass transition temperature. A final hardbake levels the effects of the process history. A high degree of crosslinking, a low drop of the dynamic modulus over temperature (30%) up to the glass transition temperature 100–140 °C were achieved for SU-8 with an exposure dose of 1500 mJ/cm², a postbake temperature of 95 °C and hardbake of 240 °C. Electrothermal actuators proved to be stable until the end of the experiment after 2400 duty cycles. Actuator deflections up to 55 μm were measured (actuator length: 4 mm) for input powers up to 160 mW and a maximum operating temperature of 120 °C. Higher temperatures led to permanent deformations and failure. An offset drift of up to 20% occurs during actuation, but converges after a burn-in phase of about two hours.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.