Surface effects are crucial in several mesoscopic phenomena, especially those concerning biological entities. Here we determine the effects of Van der Waals forces at relatively long range ( 80 nm) by optically trapping a probe particle close to a large silica particle and modulating the spatial position of the probe employing oscillating optical tweezers. This method has greater signal-to-noise in the experimentally measured probe-response as compare to that obtained from measurements of Brownian fluctuations. We quantify the H-value experimentally by analyzing the amplitude response of a single trapped particle in comparison to numerically expected results by employing chi-square fitting, and obtain good agreement with the known H-value for the system.

© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Avijit Kundu, Shuvojit Paul, Soumitro Banerjee, and Ayan Banerjee, "Measurement of Van der Waals force using optical tweezers," Proc. SPIE 11083, Optical Trapping and Optical Micromanipulation XVI, 110832G (Presented at SPIE Nanoscience + Engineering: August 15, 2019; Published: 9 September 2019); https://doi.org/10.1117/12.2529199.