Quantifying Experimental Errors in Measuring Colloidal Interaction Potentials with Optical Tweezers

Abstract

We present a systematic study on the measurement of pair interaction potentials between small particles using optical tweezers (OT), focusing on the modelling and quantification of three key experimental errors: z-motion error, dynamic error, and static error. While these errors have been previously acknowledged, their individual effects on such measurements had not been thoroughly examined. We develop a framework to model these errors and validate it through controlled experiments. By carefully tuning experimental parameters, we decouple and quantify each error source, demonstrating that they can be independently controlled and accounted for. Our approach enables a more precise access to the true interaction potential, reducing measurement ambiguities and improving the accuracy of comparisons with theoretical models. As a demonstration of the framework’s applicability, we apply our correction method to extract the depletion attraction potential from experimentally measured data, showcasing how systematic error removal enables the retrieval of physically meaningful interaction potentials. This work provides a robust methodology for enhancing the accuracy of OT-based potential measurements and for studying colloidal interactions.