Nano-Grating Force Sensor for Measurement of Neuron Membrane Characteristics Under Growth and Cellular Differentiation

We fabricated single-layer pitch-variable diffractive nanogratings on silicon nitride probe using e-beam lithography and subsequent pattern transfer techniques. The nanogratings consist of flexure folding beams suspended between two parallel cantilevers of known stiffness. The probe displacement, therefore the force, can be measured through grating transmission spectrum. We measured the mechanical membrane characteristics of PC 12 cells using the force sensors with displacement range of 10 μm and force sensitivity 8 μN/μm. Young's moduli of 425±30 Pa are measured with membrane deflection of 1% for PC 12 cells cultured on polydimethylsiloxane(PDMS) substrate coated with collagen or laminin in Ham's F-12K medium. We have also observed stimulation of directed neurite contraction up to 6 μm on extended probing for a time period of 30 minutes.