We demonstrate how optical tweezers combined with a three-dimensional force detection system and high-speed camera are used to study the swimming force and behavior of trapped micro-organisms. By utilizing position sensitive detection, we measure the motility force of trapped particles, regardless of orientation. This has the advantage of not requiring complex beam shaping or microfluidic controls for aligning trapped particles in a particular orientation, leading to unambiguous measurements of the propulsive force at any time. Correlating the direct force measurements with position data from a high-speed camera enables us to determine changes in the particle’s behavior. We demonstrate our technique by measuring the swimming force and observing distinctions between swimming and tumbling modes of the Escherichia coli (E. coli) strain MC4100. Our method shows promise for application in future studies of trappable but otherwise arbitrary-shaped biological swimmers and other active matter.

中文翻译：

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游泳力和光学捕获微生物的行为

我们演示了如何将光镊与三维力检测系统和高速相机相结合来研究被困微生物的游泳力和行为。通过利用位置敏感检测，我们可以测量捕获的颗粒的运动力，而与方向无关。这样做的优点是不需要复杂的光束整形或微流体控制来将捕获的颗粒对准特定的方向，从而可以随时对推进力进行明确的测量。将直接力测量值与来自高速相机的位置数据相关联，使我们能够确定粒子行为的变化。我们通过测量游泳力并观察大肠杆菌的游泳和翻滚模式之间的区别来证明我们的技术（大肠杆菌）菌株MC4100。我们的方法显示出可用于将来可捕获但形状任意的生物游泳者和其他活性物质的前景。