Characterizing a Live Shear-Resistant (SR-) Biofilm with Realtime Particle Tracking Micro-rheology in eChip microcosm

Environmental insults play important roles in biofilm development. Contrary to conventions, recent studies reveal that biofilm can develop under severe flow shear (e.g. >10,000 s^-1) and eventually becomes resistant to shear erosion. To understand the underlying adaptive mechanism, rheology measurement of a live biofilm must be performed as the film develops in its natural environment. Lack of tools has hindered past efforts. Here, we present the development of experimental techniques that combines long-term ecology-on-a-chip (eChip) microfluidic platform and digital holographic 3D particle tracking micro-rheology (DH-PTM) to measure the rheological evolution of a live SR-biofilm. The eChip platform provides long-term exquisitely-controlled environment to SR-biofilms, while DH-PTM tracks microbes in films and subseqently estimating viscoelasticity from 3D trajectories. Concurrent PTM measurement using newly developed 1nm quantum dot (CaO⁺) as tracers will also be performed. Techniques is applied to study SR-biofilms of P. aeruginosa and its 12 mutants.