Crab-Pincer Shaped Non-Contact Optical Fiber Tweezers

Optical tweezers facilitate non-contact manipulation, significantly minimizing cellular damage to biological samples. Among non-contact fiber-based systems, multi-core fiber optical tweezers represent a prominent category. However, the core-to-core spacing of multi-core fibers restricts tight focusing of the outgoing beam. High-precision free surface structures, fabricated using two-photon polymerization lithography (TPL) with subwavelength resolution, address this limitation. In this study, we introduce crab-pincer-shaped non-contact optical fiber tweezers developed from multi-core fibers. By substituting conventional reflective surfaces with a crab-pincer-shaped geometry, the system generates an optical trapping field through converging beams rather than diverging beams. Consequently, we achieved a smaller optical trap with an axial full width at half maximum (FWHM) of 2.73 μm. Simulations indicate that the axial trapping potential depth for polystyrene (PS) spheres with a diameter of 6 μm is 204.3 k_BT/mW, which exceeds twice that of the reflective structures. Experimentally, the crab-pincer-shaped optical fiber tweezers successfully trapped PS spheres with a diameter of 3 μm and yeast cells with a diameter of 6 μm. By preparing two crab-pincer-shaped structures on a multi-core fiber, two yeast cells can be trapped by each fiber probe. The designed crab-pincer structures can serve as a powerful tool for component fiber arrays.