This hair cell is about 30 micrometers long and the hair bundle is about 5 micrometers wide. To put these dimensions into perspective, let me compare the size of the hair cell to that of a structure that may be more familiar to this audience. This slide shows a 1 cm silicon die that contains a variety of MEMS test structures. To illustrate the size of a hair cell, I have electronically pasted the image of the hair cell to scale on this slide. You will have to zoom in on the hair cell to be able to see it.
Hair cells are small.
But hair cells are themselves complex micromechanical systems whose function relies on an array of even smaller mechanical parts. Displacements of hair bundles generate electrical responses in hair cells via mechanically sensitive ion channels in the cell membrane. Ion channels are proteins that are integral parts of the membranes of all cells. Most of the cell's membrane is lipid and acts as a chemical and electrical barrier between the inside and outside of the cell. Ion channels have pores that act as conduits for ionic currents to pass through the membrane.