טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentHaimov Yuri
SubjectOptical Characterization of Bacteria Interactions with
Micro-Structured Surfaces
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Professor Ester H. Segal
Full Thesis textFull thesis text - English Version


Abstract

The understanding of the interaction of bacteria with surfaces is remarkably incomplete. Significant research effort is devoted to investigating the effect of micro- and nano- structures on bacterial behavior, but none of them have provided conclusive results with regard to the factors that govern the process of the bacteria adhesion to the surface. The aim of this work is to investigate the factors that affect bacterial adhesion to micro-scale topologies.


Periodic micro-structured surfaces, prepared from silicon or polydimethylsiloxane (PDMS) substrates, serve as both the preferable solid-liquid interface for bacteria networking and a simultaneous optical transducing element that monitors the response of bacteria. Bacterial interactions were investigated using different micro-structured topologies, different surface chemistries, and different bacteria models. The studied surfaces were designed to exhibit a porous two-dimensional (2D) periodic structure, a form of lamellar grating. Bacterial cells capture within the pores induces measurable changes in the zero-order reflectivity spectrum, collected from the periodic structure. The first studied system is based on micro-structured porous silicon (PSi) substrates that were fabricated by DRIE (deep reactive ion etching). Different periodic microstructures were fabricated, varying in terms of their pore dimensions and connectivity, and E. coli adhesion was investigated by real-time reflectometric interference spectroscopic measurements. Once a preferential microstructure was identified, the effects of the PSi surface chemistry as well as bacteria properties (e.g., motility) were further investigated. The second studied system is based on transparent polymeric photonic crystals (PPCs) that were fabricated by replication of the micro-structured PSi substrates. These PPCs are attractive optical transducers as they allow monitoring of bacteria colonization by two simultaneous optical signals i.e., zero-order reflectivity and transmittance.

Thus, this research presents an attempt to characterize the ability of bacteria to interact with different micro-structured surfaces by new real-time and label-free optical tools.