Abstract
In order to realize a fluidic soft microactuator with a built-in control valve, this paper presents a cantilever type flexible electro-rheological microvalve (FERV) with a hybrid flow channel structure made from polydimethylsiloxane (PDMS) and SU-8. The hybrid structure provides high flexibility with the PDMS structure while only slight expansion occurred under high pressure with the SU-8 structure. In addition, its flexible electrodes are realized by UV-curable PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) that is a flexible conductive polymer and can be fabricated by simple and fast fabrication process without high-cost equipment. The proposed FERV can control the flow rate of the electro-rheological fluid (ERF) through the flow channel by changing its apparent viscosity with an applied electric field. FEM simulations were conducted to demonstrate the flexural rigidity of the designed FERV and compare it with the previous FERVs. Developing micro-electro-mechanical systems (MEMS) processes using the photolithography technique, the FERV was successfully fabricated and its characteristics were experimentally clarified. The results showed the feasibility of the proposed FERV in the soft microactuator application.
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Appendix: FEM simulations of FERVs
Appendix: FEM simulations of FERVs
The FEM simulations were conducted for investigating the SU-8 FERV, the DE-FERV, and the C + PDMS FERV. The dimensions of the simulated FERVs were shown in Fig. 13. All of the FERV flow channel dimensions were fixed at 400 μm in width, 70 μm in height and 5 mm in length. The thickness of electrodes of the SU-8 FERV and the C + PDMS FERV were 0.2 μm, while that of the thick and thin parts of electrodes of the DE-FERV were 15 μm and 10 μm, respectively, according to the previous study (Yoshida et al. 2015). The wall thickness of the DE-FERV made from PDMS were 50 μm that was equal to the wall thickness of the proposed FERV. The SU-8 wall thickness was 30 μm that was equal to the thickness of SU-8 strengthening plate of the proposed FERV. The wall thickness of the C + PDMS FERV was 200 μm in order to obtain the same flexural rigidity as that of the proposed FERV.
Dimensions used in the simulations of a SU-8 FERV, b DE-FERV, c C + PDMS FERV
The materials’ properties utilized in the simulations were shown in Tables 1 and 4. The bending simulations were conducted by fixing one end as a cantilever and a force of 50 μN was applied perpendicularly to the free end of the FERVs. Then, the FERVs’ flexural rigidity was calculated by using Eq. (3). The flow channel expansion simulations were conducted in 2D FEM by applying 100 kPa pressure to the flow channel inside. The bending and flow channel expansion simulation results were demonstrated in Figs. 14 and 15, respectively.
Bending simulation results of a SU-8 FERV, b DE-FERV, c C + PDMS FERV, d hybrid structure FERV
Flow channel expansion simulation results of a SU-8 FERV, b DE-FERV, c C + PDMS FERV, d hybrid structure FERV
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Sudhawiyangkul, T., Yoshida, K., Eom, S.I. et al. A study on a hybrid structure flexible electro-rheological microvalve for soft microactuators. Microsyst Technol 26, 309–321 (2020). https://doi.org/10.1007/s00542-019-04492-2
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DOI: https://doi.org/10.1007/s00542-019-04492-2