Mechanical Engineering MS Thesis Defense by Mr. Md. Elius
When: Monday,
July 24, 2023
10:00 AM
-
12:00 PM
Where: > See description for location
Description: Mechanical Engineering MS Thesis Defense by Mr. Md. Elius
DATE:
July 24, 2023
TIME:
10:00 a.m. - 12:00 p.m.
LOCATION:
Science & Engineering Building, Room 110 (Materials Science Lab)
TOPIC:
Study of Bacteria Super-Hydrophobic-Wall Interactions for Novel Anti-Biofouling Materials
ABSTRACT:
This thesis details the anti-biofouling property of superhydrophobic surfaces (SHS) and the improvement of the localization accuracy of particle tracking and the mechanism of wall accumulation of bacteria to understand biofilm formation using digital holographic microscopy.
To investigate the anti-biofouling properties of SHS, two types of surfaces were fabricated: a SHS with micro-grooves and micro-ridges, and a SHS with randomly roughed micro/nano-scale surface textures. The fabrication process involved sandblasting, chemical etching with HCl, boiling, and the application of a hydrophobic coating (1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane). The stability and lifetime of the air bubble (plastron) on SHSs were characterized using total internal reflection and direct imaging techniques. Following a 20-hour incubation period in a tube, the spatial distribution of bacteria was analyzed using scanning electron microscopy (SEM). To isolate the impacts of gas bubbles and surface roughness, the bacterial adhesion on rough surfaces which had the same texture geometry as that of the SHS but no chemical treatment to sustain the gas bubbles was also studied.
Accurate tracking of bacteria poses a significant challenge due to their small size and refractive index similarity to the surrounding medium. To address this issue, a new method was developed to improve tracking accuracy and particle position determination. Two optical configurations in digital holography microscopy were compared for tracking the motion of 2 μm silver-coated glass spheres in a 3D suspension. The hologram plane was positioned either outside or in the middle of the suspension, and two axially-separated holograms were recorded and processed using an iterative phase-retrieval approach. Results showed superior tracking performance when the hologram plane was located in the middle of the sample. Then, a 20x magnification configuration DHM was used to study the 3D swimming behavior of two different bacterial strains (Shewanella japonica UMDC19 and Shewanella sp. UMDC1), one of which exhibits higher concentrations near solid surfaces than the other. The experiment was conducted in a 200 µm depth glass cuvette as a sample volume. The growth of the two bacterial strains and their speeds were measured, and their motion behavior was compared using the mean square displacement method (MSD). The motion behavior was categorized into super-diffusive and sub-diffusive based on the slope of the MSD. Both strains exhibit the same sub-diffusive motion near the wall region, while their motion behavior in the bulk region is distinctly different was observed.
Throughout the thesis, this research provides insights into the mechanisms of biofilm formation and anti-biofouling properties of super-hydrophobic surfaces, which could guide the engineering design of efficient anti-biofouling materials.
ADVISOR:
-Dr. Hangjian Ling, Assistant Professor, Department of Mechanical Engineering, UMass Dartmouth
COMMITTEE MEMBERS:
-Dr. Pia H. Moisander, Professor, Department of Biology, UMASS Dartmouth
-Dr. Banafsheh Seyedaghazadeh, Assistant Professor, Department of Mechanical Engineering, UMass Dartmouth
Open to the public. All MNE students are encouraged to attend.
For more information, please contact Dr. Hangjian Ling (hling1@umassd.edu) or Sue Cunha (scunha@umassd.edu).
DATE:
July 24, 2023
TIME:
10:00 a.m. - 12:00 p.m.
LOCATION:
Science & Engineering Building, Room 110 (Materials Science Lab)
TOPIC:
Study of Bacteria Super-Hydrophobic-Wall Interactions for Novel Anti-Biofouling Materials
ABSTRACT:
This thesis details the anti-biofouling property of superhydrophobic surfaces (SHS) and the improvement of the localization accuracy of particle tracking and the mechanism of wall accumulation of bacteria to understand biofilm formation using digital holographic microscopy.
To investigate the anti-biofouling properties of SHS, two types of surfaces were fabricated: a SHS with micro-grooves and micro-ridges, and a SHS with randomly roughed micro/nano-scale surface textures. The fabrication process involved sandblasting, chemical etching with HCl, boiling, and the application of a hydrophobic coating (1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane). The stability and lifetime of the air bubble (plastron) on SHSs were characterized using total internal reflection and direct imaging techniques. Following a 20-hour incubation period in a tube, the spatial distribution of bacteria was analyzed using scanning electron microscopy (SEM). To isolate the impacts of gas bubbles and surface roughness, the bacterial adhesion on rough surfaces which had the same texture geometry as that of the SHS but no chemical treatment to sustain the gas bubbles was also studied.
Accurate tracking of bacteria poses a significant challenge due to their small size and refractive index similarity to the surrounding medium. To address this issue, a new method was developed to improve tracking accuracy and particle position determination. Two optical configurations in digital holography microscopy were compared for tracking the motion of 2 μm silver-coated glass spheres in a 3D suspension. The hologram plane was positioned either outside or in the middle of the suspension, and two axially-separated holograms were recorded and processed using an iterative phase-retrieval approach. Results showed superior tracking performance when the hologram plane was located in the middle of the sample. Then, a 20x magnification configuration DHM was used to study the 3D swimming behavior of two different bacterial strains (Shewanella japonica UMDC19 and Shewanella sp. UMDC1), one of which exhibits higher concentrations near solid surfaces than the other. The experiment was conducted in a 200 µm depth glass cuvette as a sample volume. The growth of the two bacterial strains and their speeds were measured, and their motion behavior was compared using the mean square displacement method (MSD). The motion behavior was categorized into super-diffusive and sub-diffusive based on the slope of the MSD. Both strains exhibit the same sub-diffusive motion near the wall region, while their motion behavior in the bulk region is distinctly different was observed.
Throughout the thesis, this research provides insights into the mechanisms of biofilm formation and anti-biofouling properties of super-hydrophobic surfaces, which could guide the engineering design of efficient anti-biofouling materials.
ADVISOR:
-Dr. Hangjian Ling, Assistant Professor, Department of Mechanical Engineering, UMass Dartmouth
COMMITTEE MEMBERS:
-Dr. Pia H. Moisander, Professor, Department of Biology, UMASS Dartmouth
-Dr. Banafsheh Seyedaghazadeh, Assistant Professor, Department of Mechanical Engineering, UMass Dartmouth
Open to the public. All MNE students are encouraged to attend.
For more information, please contact Dr. Hangjian Ling (hling1@umassd.edu) or Sue Cunha (scunha@umassd.edu).
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