Direct measurement of individual optical forces in ensembles of trapped particles

Posted on 11.01.2021 - 23:22
Optical tweezers are a powerful tool to hold and manipulate particles on the micro-scale. The ability to measure tiny forces enables detailed investigations, e.g., of the mechanical properties of biological systems. Here we present a generally applicable method to simultaneously mea- sure all components of the force applied to a specific particle in a trapped ensemble, or to a specific site of an extended object. The method relies on a detailed analysis of a single interfer- ence pattern formed in the far-field to recover amplitude and phase of the field. It requires no information about size, shape and optical properties of the particles. With the ability to scale to many traps — we show individual force measurements for up to 10 particles — it opens up a wealth of new opportunities made possible by localized quantitative force measurements in complex biological settings. We demonstrate force measurements when stretching a red blood cell, directly held by four traps.


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Strasser, Franziska; Moser, Simon; Ritsch-Marte, Monika; Thalhammer, Gregor (2021): Direct measurement of individual optical forces in ensembles of trapped particles. The Optical Society. Collection.


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Franziska Strasser
Simon Moser
Monika Ritsch-Marte
Gregor Thalhammer


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