Wetting and tribological behavior of micro, nano & hierarchical patterned Poly-Methyl-Metha-Acrylic (PMMA) surfaces

Title
Wetting and tribological behavior of micro, nano & hierarchical patterned Poly-Methyl-Metha-Acrylic (PMMA) surfaces
Authors
Shuxue PiaoNagaraj Chelliah MachavallavanIl-Joo Cho장경영윤의성
Keywords
Water contact angle; Tribology; PMMA; PTFE; PMMA and PTFE surfaces
Issue Date
2013-09
Publisher
World Tribology Congress 2014
Abstract
The present study concerns with wetting, and tribological behavior of different length scales of pillar patterned PMMA surfaces. The different length scales of pillar patterned PMMA surfaces are classified as micro (M), nano (N) and hierarchical surfaces (H). All pillar patterned PMMA surfaces are fabricated on silicon substrates using capillary force lithographic technique. Wetting behavior is characterized by using Water Contact Angle (WCA) measurement, and Tribological behavior is characterized by using multimode Nanoscope IIIa Scanning Probe Microscopy (Digital Instruments) with an aid of Borosilicate Spherical probe cantilever (Novascan) with particle diameter of 20 μm and spring constant of 0.60 N/m. We observed three contradictory cases from our experimental observation which are (i) For hierarchical patterned surfaces, contact angle decreases with liquid-air fraction which disobeys Cassie- Baxter model. (ii)For micro patterned PMMA surfaces; it exhibits high WCA and high friction values. (iii) PMMA is hydrophilic in nature with young contact angle of 66.7, but it shows hydrophobic behavior with WCA > 90 even with moderate roughness factor (1.5 to 3.5). All the above cases are explained based on roughness factor and liquid-air fraction, fL-A. First case indicates us that when fL-A is very high, stability of Cassie-Baxter regime is questionable and transition to meta-stable Cassie-Baxter exists in case of nano patterned surfaces and Wenzel state in case of hierarchical patterned PMMA surfaces. It is worth to note that fL-A is in the range of 0.55 for micro-patterned PMMA surfaces, 0.80 for nano patterned PMMA surfaces, and 0.94 for hierarchical patterned PMMA surfaces. This is confirmed with an experimental fact that increase of WCA with increased roughness factor in case of hierarchical patterned PMMA surfaces. Second case tells us that more the stability of Cassie-Baxter regime, more the fric
URI
http://pubs.kist.re.kr/handle/201004/47276
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KIST Publication > Conference Paper
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