Development of polymer electrostatic comb-drive actuator using hot embossing and ultraprecision cutting technology

Abstract

We report the fabrication and evaluation of a PMMA electrostatic comb-drive microactuator using hot embossing and ultra-precision cutting technology. First, a two-step silicon mold is fabricated by bulk micromachining technology. Next, comb-drive microactuator structures are formed on a PMMA plate by hot embossing. Both finger width and gap between fingers are 5 m, and finger thickness is larger than 70 m. Then, the PMMA layer that remained after hot embossing is removed by ultra-precision cutting to release the movable parts. Last, the device is coated with a gold layer for the electrode. The PMMA combdrive microactuator has been tested successfully.

Development of polymer MEMS process technology as an approach to a sustainable production system

“…Polymer materials have several advantages over silicon material, such as much lower stiffness, transparency, higher coefficient of thermal expansion, better biocompatibility and the fact that they are environmentally friendly [1], lower material cost, and easier fabrication by mass-replication technologies, e.g. injection molding, hot embossing [2]. The transparency of PMMA is important for optical devices, such as lenses, waveguides, etc [3], and optical-based biomedical or microfluidic devices.…”

“…However, heat generation during the O 2 plasma strongly affected the surface of the device. In our group, recently in [2], ultra-precision cutting was used to remove the thin PMMA layer remaining after the hot embossing process. However, ultra-precision machining has low productivity and high cost.…”

Novel fabrication process for a monolithic PMMA torsion mirror and vertical comb actuator

“…Furthermore, the main materials of the polymer-MEMS are polymers, which are more advantageous than silicon in terms of low cost, unique properties, substrate size flexibility, and ease of processing [1]. PMMA (polymethylmethacrylate) is one of the most frequently used polymers in MEMS because it is compatible with many mass-replication techniques, such as injection molding [2], hot embossing [3,4] and x-ray lithography [5][6][7]. Moreover, PMMA has excellent transparency in the visible light range, low stiffness, high coefficient of thermal expansion (CTE), good biocompatibility and environmental friendliness [8][9][10][11][12].…”

“…The transparent property of PMMA is important for optical devices, such as lens, waveguide [13][14][15][16][17], and optical-based biomedical or microfluidic devices [3,18,19]. Small Young's modulus and high thermal expansion of PMMA are advantages for electrostatic [4,20] and thermal actuators [21,22], respectively, because they require less power than their silicon counterparts to produce the same displacement.…”

“…Because the O 2 plasma was used to remove a PMMA layer undesirably remaining after the hot embossing process, the surface quality and microstructures might be affected by the heat generated during the O 2 plasma process. In our recent report, by using elliptical vibration cutting, we could avoid using the RIE process to remove this PMMA layer, and therefore, overcome this problem and successfully develop the lateral PMMA actuator [4]. Basically, our proposed method can be applied for a variety of polymers, and the development of monolithic polymer-MEMS devices is straightforward.…”