Application of Engineered Micro/Nano-materials in Anti-Bacterial Surfaces

Abstract

Adhesion of antigens on surfaces plays an important role in the spread of many infectious diseases. Although water-repellent surfaces are widely used for the long-term repellency of aqueous solutions, their repellency to pathogen-containing microdroplets is elusive.

Firstly, microdroplets from picoliter to nanoliter were successfully generated in a controlled manner to mimic the exhaled microdroplets in sneezing and coughing, which allowed us to evaluate the adhesion of microdroplets on both superhydrophobic (SH) and lubricant-infused “slippery” surfaces. The impact and retention of water microdroplets on these two water-repellent surfaces were compared and investigated.

Based on the result of microdroplet adhesion on water-repellent surfaces, we introduced slippery surfaces with localized lubricant menisci to directionally transport single water microdroplets. Hydrogel dots were integrated onto slippery surface to form a non-uniformly distributed lubricant layer which serves to drive microdroplets by creating an asymmetric oil layer around the droplets. This approach allows the continual transportation of water microdroplets with self-enhanced driving ability. We revealed the underlying driving mechanism and demonstrated that the meniscus-based droplet driven system can be applied to the collection of microdroplet-mediated bacteria.

Finally, based on our study of adhesion of antigens on different surfaces, we investigated the disinfection of bacteria contained in microdroplets. In our experiment we found the wetting of microdroplets on superhydrophilic silicon nanowire is very fast. This process will exert a penetration force on the bacteria inside the microdroplets. We evaluated the ability of silicon nanowire to disinfect the aerosolized bacteria. Two parameters were investigated in this project which were the droplet size of bacteria suspension and the concentration of the bacteria in the droplet. We found silicon nanowire to have a higher killing efficiency for small droplets.

Date of Award	4 Sept 2018
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Xi YAO (Supervisor) & Yung Fu CHANG (External Co-Supervisor)