Cost-Effective Optical Tweezing with the Open Flexure Microscope

Optical tweezers enable the precise manipulation of microscopic particles using lasers. Because of their high cost, they remain unattainable for underfunded institutions. We have designed and built a cost-effective optical tweezer using a modified 3-D printed OpenFlexure Microscope. This open-source inverted microscope is designed for accessibility, modularity, and precision. The design uses Raspberry Pi control for smooth, three-axis motor motion crucial to stable optical trapping. The optical tweezer incorporates a visible HeNe laser into the optical path, for ease of use, which is reflected into the OpenFlexure microscope to create a single-beam trap capable of manipulating particles such as microspheres and pollen. The system uses simple, inexpensive optics, resulting in a build cost of less than $5,000, a fraction of the price of commercial systems. The setup features an adjustable three-axis stage for sample positioning and beam alignment. Beam collimation is achieved through an adjustable pair of expanding lenses that ensures uniform focus at the trapping plane, improving trap stability and control. By reducing costs and simplifying assembly, this project makes optical experimentation accessible to underfunded institutions.