This experiment presents a new approach to measure elasticity parameters of lipid bilayers. We have deposited a stack of phospholipid bilayers on a silicon surface grating defined by e-beam lithography. The periodic surface profile acts as a boundary condition which imposes a controlled strain in the smectic film. Probing this distortion field by neutron reflectometry, we determine the smectic penetration length $\Lambda=\sqrt{K/B}$ from the relative intensity of the satellite peaks.