A Low-Cost Optical Tweezer Based on a Modified OpenFlexure Inverted Microscope  

Optical tweezers require precise optical alignment, high numerical-aperture focusing, and mechanical stability, which traditionally limits their use to well-funded research laboratories. We meet these requirements using a low-cost, open-source microscope platform and readily available optical components. We constructed a functional optical tweezer using a modified OpenFlexure 3D-printed inverted microscope and a single-beam optical trap formed with a visible HeNe laser coupled into the microscope’s optical path.

We built the complete system for under $3,000, compared to $20,000 or more for the least expensive commercial optical tweezer systems. We achieved stable trapping of micron-scale particles, confirming that reliable optical tweezing is possible at substantially reduced cost. The microscope platform provides three-axis positioning via stepper motors, which allows reproducible alignment and stable trapping. The use of a visible-wavelength laser simplifies alignment and improves safety and accessibility for student and small-laboratory environments.

This work focuses on demonstrating a stable and replicable optical tweezer. In future work, we will incorporate back focal plane detection to enable quantitative measurements of particle position and optical trapping forces. This project demonstrates that open-source hardware, additive manufacturing, and low-cost optics can support meaningful optical tweezing experiments in AMO physics.