Anti-biofouling Properties of Super-hydr

Anti-biofouling Properties of Super-hydrophobic Surfaces

Research Title: Anti-biofouling properties of super-hydrophobic surfaces(SHS) in marine environment.

Supervisor: Dr. Hangjian Ling, University of Massachusetts Dartmouth

Goal: This study helps to understand the mechanism how SHS prevents biofilm growth. It is the air layer

on SHS prevent bacteria attachment.

Summary: In this work, we fabricated three Aluminum(Al) different hierarchical structure surfaces like micro-scale roughness, nano-scale roughness and combination of micro-nano scale roughness. To fabricate these texture, first we did sandblasting with 70-270 grit size, 10 minutes ultrasonication for cleaning then we etched the surface in 18% HCl solution for 90 sec. This was the procedure to fabricate micro-scale roughness after that fabrication we kept the sample in FOTS solution for 24 hours which change the surface chemistry and make it superhydrophobic, we got the water contact angle for this micro-scale roughness is around 153 degree. For micro-nanoscale rougnesss after sandblasting, etching , we boiled the sample for 25 minutes which created nanoscale scale roughness on the surfaces. Just for nano-scale roughness, we boiled smooth Al surfaces. The highest water contact we found on micro-nano scale roughness, was around 158 degrees.

Figure 1: SEM images of three different scale roughness: micro-scale, nano-scale, and combination of micro-nano scale

Experimental set up for anti-biofouling test:

Smooth aluminum (SM) and Super-hydrophobic (HS) strips.
Bacteria grow for 20 h at 27 Celsius in suspension with strips in incubation tubes
Chemical processing for drying the strip surfaces
Scanning Electronic microscope

Tools used in this project:

machine shop for strips cutting & sandblasting
Chemistry lab for etching
Anti-biofouling test (growth in suspension) collaboration with Biology department
Gold sputter coating before SEM
SEM room for imaging

Figure 2: SEM images of three different texture and their corresponding water contact angel(WCA) (a) micro-scale roughness (b) nano-scale rougness , and (c) combination of micro-nano scale roughness

The best super-hydrophobic surface, combination micro-nano scale roughness,

are prepared for anti-biofouling test. Both smooth and best SHS strips are allowed to grow

in bacterial suspension for 20 hrs at 27 Celsius. After taking out from suspension, sample

are prepared for SEM imaging. So far, from SEM imaging, we are observing bacteria are

accumulated on tip of the hills. Bacteria are not seen in the holes. The micro-size holes are

filled up with air bubbles which resist bacteria accumulated in the holes. Similarly, we also

observe same phenomenon for ordered groove surfaces. These results suggest that air

bubbles on SHS surface resist bacterial attachment on the surface.

Figure 3: Anti-biofouling test setup

Figure 4. Impact of air bubbles on the antimicrobial behavior of micro/nanostructured SHSs (a) SEM image of after anti-biofouling test (b) no bacteria in the gap due to air-bubbles(c) bacteria attachment on the hill of the SHS substrate

Figure 5: Impact of air bubbles on the antimicrobial behavior of the groove surface

To validate the idea that air-layer prevent bacterial attachment, we again performed anti-biofouling test for both rough and groove surfaces without coating. We found the presence of bacteria everywhere including the gaps and grooves of the sample. We observed the air layer on both rough and groove surface using total internal reflection.

For more details, please refer to

M. Elius, S. Richard, K. Boyle, W.S. Chang, P. H. Moisander, H. Ling, Impact of gas bubbles on bacterial adhesion
on super-hydrophobic surfaces. Results in Surfaces and Interfaces vol. 15, 100211(2024)

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Anti-biofouling Properties of Super-hydrophobic Surfaces

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