Biological near-field scanning optical microscopy: instrumentation and sample issues for shear-force feedback

The current technology of near-field microscopy is limited in two important aspects: photon throughput and scan rate. In this paper we will consider the second limitation only. Furthermore, we will consider it as a function of probe-sample feedback response time and not one of low light level imaging; i.e. scan times are not limited by any need to integrate the optical signal. Our considerations will focus on shear-force feedback response times and how it places a limit on the type of biological investigations that can be accomplished.