Experimental modeling of fluid homeostasis in the mammalian hearing organ

The mammalian hearing organ (cochlea), contains a long microfluidic channel where the ion concentration must be homogenized to enable the sensor cells that allow hearing. We hypothesize that homeostasis is achieved not only through diffusion, but by advective mixing caused by peristaltic flow in the cochlea. By determining the relevant physical parameters in the cochlea and applying fluid mechanics scaling laws, we design an apparatus that replicates conditions in the cochlea. Our apparatus consists of a square channel with a flexible wall what can be actuated to induce a flow in the channel. We seek to characterize the induced flow by using a particle imaging velocimetry system and calculating particle paths. Theory suggests that at the Reynolds number in the cochlea (Re ≈ 80) mixing will occur. We experimentally test a spectrum of parameters to verify theory predictions. The parameter region we study is also relevant for understanding other biophysical phenomena, as peristalsis is a common mechanism found in biological systems.