Research Experiences for Undergraduates (REU)
2019 Mechanical Engineering Opportunities
Name: Jong-Hoon Nam and Douglas Kelley
Department: Mechanical Engineering
Research area: Mechanically-facilitated cochlear fluid homeostasis
Lab website (Nam) / Lab website (Kelley)
Different types of hearing loss/difficulty are ascribed to the failure/disturbance of subtle balance between two types of lymphatic fluids in the cochlea. The cochlea operates like an electrochemical battery. The cochlea is partitioned into three compartments filled with the lymphatic fluids. The separation of the two fluids provides an electric potential of approximately 80 mV that is crucial for hearing. To transduce sounds into neural impulses, there exists constant leaking (depolarizing) currents between the two fluid spaces though the sensory epithelium called the organ of Corti. Supporting cells in the organ of Corti must transport ions to maintain the electric potential. According to current theory, cochlear fluid homeostasis is responsible for the loss of auditory receptor cells (hair cells). The PIs propose to examine the converse of the current theory: they hypothesize that the mechanical feedback of auditory receptor cells facilitates the maintenance of cochlear fluid homeostasis.
This proposed project challenges the assumption of diffusion-limited ionic transport in the cochlear fluid. Recent observations show unique deformation patterns of the organ of Corti due to active mechanical feedback of the hair cells. This project aims to connect the active organ of Corti mechanics with the cochlear fluid homeostasis by demonstrating a different mode of ion transport—peristaltic fluid mixing. Specifically, it will be shown that: 1) the electromotility of outer hair cells generates peristaltic fluid motions in the organ of Corti, and 2) the peristaltic fluid motions help to homogenize cochlear fluids. This proposed project will transform hearing science by integrating two research domains that have not been considered together: mechanics and ion homeostasis of the cochlea. The unique expertise of Drs. Nam and Kelley is crucial for the success of this ambitious project. Nam has a solid research record in hair cell physiology, cochlear micro-mechanics, and finite element analysis. Kelley has expertise in experimental fluid dynamics, especially in the mixing and reaction of solutes within viscous fluids.
Name: Jong-Hoon Nam
Department: Mechanical Engineering
Research area: Mechano-transduction of the inner ear sensory organ
We study the mechano-transduction of the inner ear. The cochlea, the mammalian hearing organ, turns mechanical stimuli (sounds) into neural signals. The identification of mechanical properties of cochlear sensory cells and tissues is crucial to better understand how we hear (or fail to hear). To measure the mechanical properties, we need to apply calibrated pressures in the order of mPa and measure displacements in nanometers at the frequency of up to tens of kHz. Students will participate in measuring mechanical responses of artificial and biological micro structures in a micro-fluidic chamber system. Through this project, students will learn how the principles of acoustics, fluid dynamics, solid mechanics and vibrations are applied to micro-mechanical experiments with biological tissues. Also students will gain experiences with vibration measurement, imaging and data acquisition devices.