Incoherent Optical Tweezers on Black Titanium

Optical tweezers enable the manipulation of micro- and nanodielectric particles through entrapment using a tightly focused laser. Generally, optical trapping of submicron size particles requires high-intensity light in the order of MW/cm(2). Here, we demonstrate a technique of stable optical trapping of submicron polymeric beads on nanostructured titanium surfaces (black-Ti) without the use of lasers. Fluorescent polystyrene beads with a diameter d = 20-500 nm were successfully trapped on black-Ti by low-intensity focused illumination of incoherent light at lambda = 370 m from a Hg lamp. Light intensity was 5.5 W/cm(2), corresponding to a reduced light intensity of 6 orders of magnitude. Upon switching off illumination, trapped particles were released from the illuminated area, indicating that trapping was optically driven and reversible. Such trapping behavior was not observed on nonstructured Ti surfaces or on nanostructured silicon surfaces. Thus, the Ti nanostructures were demonstrated to play a key role.

Automated summary

Optical tweezers can stably trap submicron particles on black-Ti surfaces using low-intensity focused light, demonstrating optically driven and reversible trapping behavior. The Ti nanostructures were shown to play a key role in this trapping technique as trapping was not observed on nonstructured Ti or nanostructured silicon surfaces.