Design and Fabrication of Polymer Electrostatic Comb-Drive Actuators for Micro Conveyer Systems

Abstract

We report a design, simulation and preliminary fabrication of Micro Conveyer System (MCS) based on polymer electrostatic comb-drive actuators using polymethylmethacrylate (PMMA). This MCS consists of linear comb actuators, rotational comb actuators, micro containers, rollers and a ratchet mechanism. Micro containers, used for carrying micro and nano samples such as protein, cells, are moved by comb-actuators through the ratchet mechanism. They can move straight, turn left or right. Each module of MCS, which has dimension of 1x1cm 2 , can be assembled to create more complex conveyance systems for different applications (Fig. 1).To prove the working principle of the ratchet mechanism and the MCS, silicon MCS with the same design was fabricated first, (Fig. 2). Movement of the micro container has been tested with driving voltage (Vpp) of 100V, and driving frequency ranges from 1Hz to 50Hz.To fabricate a PMMA comb-drive actuator, a silicon mold has to be fabricated first by using silicon wafer and ICP-RIE process, and then hot embossing will be applied to fabricate the MCS, (Fig. 3). A PMMA substrate is hot embossed by using the silicon mold and embossing jig. Embossing temperature, molding force and embossing time are 180°C, 4500N and 10 minutes, respectively. De-molding is performed at 80°C with de-molding rate is 1µm/min.Second method to fabricate PMMA MCS is using X-ray lithography. This method will feature very high aspect ratio and very smooth surface.Salient advantages of PMMA comb-drive actuators and MCS are low cost, high throughput and consuming less energy compared with the counterpart using silicon because PMMA has a lower Young's modulus. The simulation results show that the driving voltage in PMMA actuator is almost hundred times smaller than that of silicon actuator with the same dimension. MemberWe propose the design, simulation and preliminary fabrication of Micro Conveyer Systems (MCS) based on polymer electrostatic comb-drive actuators using polymethylmethacrylate (PMMA). This MCS consists of linear comb actuators, rotational comb actuators, micro containers, and a ratchet mechanism. Micro containers, used for carrying micro and nano samples such as protein, cells, are moved by comb-actuators through the ratchet mechanism. The silicon MCS was fabricated and checked to confirm characteristics and working principles. Each PMMA MCS, which has dimension of 1x1cm 2 , will be fabricated by using hot embossing technique or X-ray lithography. A silicon mold has to be fabricated first by using silicon wafer and ICP-RIE process. Salient advantages of PMMA comb-drive actuators are low cost, high throughput and consuming less energy compared with the counterpart using silicon because PMMA has a lower Young's modulus.

Fabrication and Characterization of Smooth Si Mold for Hot Embossing Process

“…The minimum feature size was 2µm and the thickness of structure was 30µm, which makes the aspect ratio of 15. Figure 10 shows PMMA comb-drive actuators and ratchet mechanism, which will be used in Micro Conveyer System (9) .…”