Characterizing the mechanical properties of biofilms using Atomic Force Microscopy AFM*

Biofilms are a microbially derived sessile community characterized by cells embedded in a polymer matrix. Measuring the material properties of live biofilms without perturbing them is known to be difficult. Atomic Force Microscopy (AFM) is a great tool for imaging the topology and conducting force-distance-based studies to characterize their mechanical properties. This study uses AFM to characterize the viscoelasticity of biofilms generated by different species:  P. aeruginosa, P. fluorescein, and E. coli. Biofilms are first grown on a functionalized glass slide in a microfluidic channel for nanoindentation experiments, and the force-distance curves are obtained. Using the force-distance curves, the contact point is determined to obtain the force-indentation curve. Next, the integration time history is used to model the force curve with Ting's integration and determine the viscoelasticity parameters. The models used for Ting's integral include Hertz, Standard Linear Solid (SLS), Power-law Rheology (PLR), and Maxwellian models. Statistical comparisons of the viscoelastic parameters between species and strains will be conducted.