Bio-inspired surfaces with superamphiphobic properties are well known as effective candidates for antifouling technology. However, the limitation of large-area mastering, patterning and pattern collapsing upon physical contact are the bottleneck for practical utilization in marine and medical applications. In this study, a roll-to-plate nanoimprint lithography (R2P NIL) process using Morphotonics’ automated Portis NIL600 tool was used to replicate high aspect ratio (5.0) micro-structures via reusable intermediate flexible stamps that were fabricated from silicon master molds. Two types of Morphotonics’ in-house UV-curable resins were used to replicate a micro-pillar (PIL) and circular rings with eight stripe supporters (C-RESS) micro-structure onto polycarbonate (PC) and polyethylene terephthalate (PET) foil substrates. The pattern quality and surface wettability was compared to a conventional polydimethylsiloxane (PDMS) soft lithography process. It was found that the heights of the R2P NIL replicated PIL and C-RESS patterns deviated less than 6% and 5% from the pattern design, respectively. Moreover, the surface wettability of the imprinted PIL and C-RESS patterns was found to be superhydro- and oleophobic and hydro- and oleophobic, respectively, with good robustness for the C-RESS micro-structure. Therefore, the R2P NIL process is expected to be a promising method to fabricate robust C-RESS micro-structures for large-scale anti-biofouling application.

A key way to prevent undesirable fouling of any structure in the marine environment, without harming any microorganisms, is to use a polymer film with high hydrophobicity. The polymer film, which was simply prepared from a blend of hydrophobic polydimethylsiloxane elastomer and hydrophilic polyurethane, showed improved properties and economic viability for antifouling film for the marine industry. The field emission scanning electron microscope and energy dispersive X-ray spectrometer (FESEM and EDX) results from the polymer blend suggested a homogenous morphology and good distribution of the polyurethane disperse phase. The PDMS:PU blend (95:5) film gave a water contact angle of 103.4° ± 3.8° and the PDMS film gave a water contact angle of 109.5° ± 4.2°. Moreover, the PDMS:PU blend (95:5) film could also be modified with surface patterning by using soft lithography process to further increase the hydrophobicity. It was found that PDMS:PU blend (95:5) film with micro patterning from soft lithography process increased the contact angle to 128.8° ± 1.6°. The results from a field test in the Gulf of Thailand illustrated that the bonding strength between the barnacles and the PDMS:PU blend (95:5) film (0.07 MPa) were lower than the bonding strength between the barnacles and the carbon steel (1.16 MPa). The barnacles on the PDMS:PU blend (95:5) film were more easily removed from the surface. This indicated that the PDMS:PU blend (95:5) exhibited excellent antifouling properties and the results indicated that the PDMS:PU blend (95:5) film with micro patterning surface could be employed for antifouling application.

Biofilm-associated infections caused by an accumulation of micro-organisms and pathogens significantly impact the environment, health risks, and the global economy. Currently, a non-biocide-releasing superhydrophobic surface is a potential solution for antibacterial purposes. This research demonstrated a well-designed robust polydimethylsiloxane (PDMS) micro-structure and a flame treatment process with improved hydrophobicity and bacterial anti-adhesion properties. After the flame treatment at 700 ± 20 °C for 15 s, unique flower-petal re-entrant nano-structures were formed on pillars (PIL-F, width: 1.87 ± 0.30 μm, height: 7.76 ± 0.13 μm, aspect ratio (A.R.): 4.14) and circular rings with eight stripe supporters (C-RESS-F, width: 0.50 ± 0.04 μm, height: 3.55 ± 0.11 μm, A.R.: 7.10) PDMS micro-patterns. The water contact angle (WCA) and ethylene glycol contact angle (EGCA) of flame-treated flat-PDMS (FLT-F), PIL–F, and C–RESS-F patterns were (133.9 ± 3.8°, 128.6 ± 5.3°), (156.1 ± 1.5°, 151.5 ± 2.1°), and (146.3 ± 3.5°, 150.7 ± 1.8°), respectively. The Escherichia coli adhesion on the C-RESS-F micro-pattern with hydrophobicity and superoleophobicity was 42.6%, 31.8%, and 2.9% less than FLT-F, PIL-F, and Teflon surfaces. Therefore, the flame-treated C-RESS-F pattern is one of the promising bacterial anti-adhesion micro-structures in practical utilization for various applications.

The objective of this research work is to propose a phase diagram that can be used to find a proper operating condition for generating droplets of different types. It is found that the phase diagram of Q_R versus Ca_D can effectively classify the droplet generation into three vivid regimes: dripping, jetting and tubing. For the dripping regime, its operating condition is in the range of either Ca_D < 10⁻⁴ and Q_R < 50 or 10⁻³ < Ca_D < 10⁻⁴ and Q_R < 1. For the jetting regime, its operating condition is in the range of either Ca_D < 1.35 × 10⁻² and Q_R > 100 or Ca_D > 1.35 × 10⁻² and Q_R > 1. For the tubing regime, its operating condition is in the range of Ca_D > 1.35 × 10⁻² and Q_R < 1.