Jump to Main Content
Absolute position total internal reflection microscopy with an optical tweezer
- Liu, Lulu, Woolf, Alexander, Rodriguez, Alejandro W., Capasso, Federico
- Proceedings of the National Academy of Sciences of the United States of America 2014 v.111 no.52 pp. E5609
- fluorescence, fluorescence microscopy, image analysis, light intensity, optical traps
- A noninvasive, in situ calibration method for total internal reflection microscopy (TIRM) based on optical tweezing is presented, which greatly expands the capabilities of this technique. We show that by making only simple modifications to the basic TIRM sensing setup and procedure, a probe particle’s absolute position relative to a dielectric interface may be known with better than 10 nm precision out to a distance greater than 1 μm from the surface. This represents an approximate 10× improvement in error and 3× improvement in measurement range over conventional TIRM methods. The technique’s advantage is in the direct measurement of the probe particle’s scattering intensity vs. height profile in situ, rather than relying on assumptions, inexact system analogs, or detailed knowledge of system parameters for calibration. To demonstrate the improved versatility of the TIRM method in terms of tunability, precision, and range, we show our results for the hindered near-wall diffusion coefficient for a spherical dielectric particle.