Hydrophobic Polyimide Surfaces Fabricated by Hot Embossing Method

1. Advanced MEMS Device Fabrication Hydrophobic Polyimide Surfaces Fabricated by Hot Embossing Method Adviser: W.L. Li（李旺龍教授） Lecturer : Y.K. Tsao（曹韻國） Date: 2009/06 Lab. Engineered Materials for Biomedical Applications (EMBA) 生物醫學應用實驗室

2. Outline • Introduction • Material and method • Results • Conclusion • Future work

3. Introduction Nanoimprint technology is a new method for micro/nano fabrication. There are many ways in this technology; one of them is the Hot Embossing method The definition of nanoimprint technique is “Use a nanostructure patterned mould to transfer the pattern onto specific materials by some ways, like embossing, UV exposure etc.”

4. In our study, we want to improve the surface morphology of the polyimide (PI) film by Hot Embossing method. Polyimide film often be used in the LCD industry as a alignment layer. However, PI is hydrophilic, and the liquid crystal molecular cannot align well on the PI film. So our experiment will make a hydrophobic, patterned, and liquid crystal molecular easy aligned surface. Fig.1 shows the Hot Embossing method step by step

5. Spin coating polyimide film on substrate substrate substrate Peel off the mould Si mould weight Place the mould on the film Si mould substrate substrate Hot Figure 1. The process of the Hot Embossing technique.

6. Material and method Spinning PI Film Bake the film Dehydration Substrate prepare OTS coating Si Mould prepare Lithography process Hot embossing Contact angle SEM

7. OTS Immersing Use OTS as the anti-stiction Solvent: Toluene (high purity) Solute: OTS (Octadecyltrichorosilane) We formulate this OTS solution as 1 vol.% Then put it for 24 hours

8. Hot embossing process

9. Hot embossing process

10. Material and method PI Polyimide

11. Pretilt Angle of Liquid Crystals and Liquid-Crystal Alignment on Microgrooved Polyimide Surfaces Fabricated by Soft Embossing Method Da-Ren Chiou and Li-Jen Chen* Department of Chemical Engineering, National Taiwan UniVersity, Taipei 10617, Taiwan Chein-Dhau Lee Materials and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31015, Taiwan ReceiVed June 29, 2006. In Final Form: August 23, 2006 In this study, the soft embossing method is proposed to fabricate periodical microgrooved structure on polyimide surfaces. These microgrooved polyimide surfaces are assembled to form liquid-crystal cells. It is found that the director of liquid crystals uniformly aligns along the groove direction even when the groove width is as high as 3 um. The anchoring energy of these microgrooved polyimide surfaces is higher than that of the typical rubbed surfaces. The pretilt angle of liquid crystals is adjusted by tuning the surface polarity of the polyimide alignment layer, which is identified by the advancing contact angle of water. The surface polarity of polyimide alignment layers is manipulated by simply mixing two kinds of polyimide: a more hydrophilic one and a more hydrophobic one. It is found that the pretilt angle of liquid crystals increases along with the advancing contact angle of water on the alignment layer under the condition of a fixed surface topography.

13. Results

14. Results

18. Future work • Buy the liquid crystal to test the pretilt angle • Etching the PI film, to create the second nanostructure on the surface

20. Thanks for attention!