Fabrication and characterization of the nano- and micro-particles applied dry adhesives

나노 또는 마이크로 입자의 전사를 이용한 건식 접착제의 제조 및 특성 분석

Abstract

In this study, the micro- and nano-particles were used and their shapes were transferred into the polydimethylsiloxane (PDMS) film to fabricate the dry adhesives and their properties were investigated. The Cu nanoparticles of the sizes of 20 nm, 40 nm and 70 nm and the polymethylmethacrylate (PMMA) beads of the size of $5{\mu}m$ were used to transfer their images and the resultant properties of the dry adhesives were compared. The effects of particle size and materials on the mechanical property, tensile adhesion strength, light transmittance, surface morphology, water contact angle were studied. The dry adhesives obtained from the transfer process of Cu nanoparticles with the size of 20 nm resulted in the enhancement of tensile adhesion strength more than 300% compared to that of the bare PDMS. The formation of nanostructure of large surface area on the surface of the PDMS film by the Cu nanoparticles may responsible for the improvement. This study suggests that the use of nanoparticles during the fabrication of PDMS dry adhesives is easy and effective and could be applied to the fabrication of the medical patch.

본 연구에서는 마이크로 또는 나노 입자 형상을 폴리디메틸실록산 (PDMS)에 전사시켜 건식접착제를 제조하고 특성에 대하여 고찰하였다. 20 nm, 40 nm, 70 nm의 직경을 가지는 구리 나노 입자형상과 $5{\mu}m$의 직경을 가지는 폴리메틸메타아크릴레이트 (PMMA) 마이크로 입자 형상을 전사시켜 PDMS 건식 접착제를 제조하였다. 입자의 종류 및 크기가 변화함에 따라 건식 접착제의 기계적 특성, 인장 접착강도, 표면 형상, 접촉각, 광학적 성질에 미치는 영향을 조사하였다. 20 nm 직경을 가지는 구리 나노 입자를 전사시켜 얻은 건식 접착제는 bare PDMS 필름에 비하여 300% 이상 향상된 인장 접착강도를 가졌다. 나노 입자를 전사시켜 얻은 큰 표면적 건식 접착제 구조가 높은 인장 접착강도를 부여하는 원인으로 추정된다. 본 연구결과는 나노 입자를 전사시키는 방법이 PDMS 건식 접착제의 제조에 있어 쉽고 효과적임을 시사한다.

Figure 1. Structure of PDMS.

Figure 4. Stress-strain curves of the bare PDMS, Cu nanoparticle and PMMA bead transferred PDMS film.

Figure 5. Laser microscope surface images of transferred PDMS dry adhesives (a) Cu NPs of 20 nm, (b) Cu NPs of 40 nm, (c) Cu NPs of 70 nm, and (d) PMMA beads of 5 μm diameter.

Figure 6. Tensile adhesion strength of the bare PDMS and various sizes of Cu nanoparticle transferred PDMS films.

Figure 7. Light transmittance as a function of the particle sizes of Cu nanoparticles.

Figure 8. Water contact angle of (a) bare PDMS (b) Cu NPs of 20 nm, (c) PMMA beads of 5 µm transferred PDMS dry adhesives.

Figure 2. Schematic steps to prepare a micro- and nano-structured PDMS film.

Figure 3. (a) High precision texture analyzer, (b) Magnified view of the probe and sample.