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

Winterstein, Thomas and Staab, Matthias and Nakic, Christian and Feige, Hans-Jürgen and Vogel, Jürgen and Schlaak, Helmut F. (2014):
SU-8 Electrothermal Actuators: Optimization of Fabrication and Excitation for Long-Term Use.
In: Micromachines, Special Issue Microactuators, MDPI, pp. 1310-1322, ISSN 2072-666X, [Online-Edition: http://www.mdpi.com/2072-666X/5/4/1310],
[Article]

Abstract

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.

Item Type: Article
Erschienen: 2014
Creators: Winterstein, Thomas and Staab, Matthias and Nakic, Christian and Feige, Hans-Jürgen and Vogel, Jürgen and Schlaak, Helmut F.
Title: SU-8 Electrothermal Actuators: Optimization of Fabrication and Excitation for Long-Term Use
Language: English
Abstract:

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.

Journal or Publication Title: Micromachines, Special Issue Microactuators
Publisher: MDPI
Uncontrolled Keywords: electrothermal actuator; SU-8; long-term stability; pseudo-bimorph; glass transition temperature
Divisions: 18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design
18 Department of Electrical Engineering and Information Technology > Institute for Electromechanical Design > Microtechnology and Electromechanical Systems
18 Department of Electrical Engineering and Information Technology
Date Deposited: 19 Dec 2014 16:16
Official URL: http://www.mdpi.com/2072-666X/5/4/1310
Identification Number: doi:10.3390/mi5041310
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