Bacterial detachment from hydrophilic and hydrophobic surfaces using a microjet impingement

In this paper, we present the use of a submerged laminar microjet impingement to evaluate the adhesion strength of Pseudomonas stutzeri onto the hydrophilic glass and hydrophobic ITO-coated glass surfaces. The detachment strength of this bacterial strain was determined from the measurement of the shear and tensile stresses necessary to erode the adhered bacteria from both tested materials surfaces. Different combinations of Reynolds number and exposure time for each combination of bacteria/substratum were used in this work to examine their effect on the bacterial detachment. Furthermore, in a qualitative study, the hydrophobicity in terms of contact angle and surface free energy of both the bacteria and substrata was determined. Also, the adhesion free energy of the bacteria on both supporting materials was quantified using the thermodynamic approach of Lifshitz van der Waals and acid/base interactions. The adhesion strength measurements were found to be in agreement with the calculations of the adhesion free energies of the bacterial strain on both substrata.