Absolute Position Total Internal Reflection Microscopy with an Optical Tweezer

TL;DR

This paper introduces a non-invasive calibration method for Total Internal Reflection Microscopy using optical tweezers, achieving over 10 nm precision and extending measurement range, enhancing TIRM's accuracy and versatility.

Contribution

The authors present a simple modification to TIRM that allows absolute position measurement with high precision and range, surpassing conventional calibration methods.

Findings

Achieved better than 10 nm positional accuracy.

Extended measurement range beyond 1 μm from surface.

Demonstrated improved calibration with hindered diffusion measurements.

Abstract

A non-invasive, 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 $\mu$m from the surface. This represents an approximate 10x improvement in error and 3x 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 calculations or inexact system analogs 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.