OPTICAL TWEEZERS: Imaging lets optical tweezers 'feel the force'

摘要

A low-cost, imaging-based force-feedback device has been created that allows users to perceive real Brownian motion and viscosity when using optical tweezers; in effect, the user can "feel the force" exerted as objects are manipulated by a trapped bead. The device is the result of a collaborative effort by researchers from the Universite Pierre et Marie Curie (Paris, France), CEA Laboratoire Interfaces Sensorielles (Fontenayaux-Roses, France), the University of Glasgow (Glasgow, Scotland), and the University of Bristol (Bristol, England). Optical tweezers are in widespread use for the micromanipulation of objects in cell biology, nanotechnology, and micro-engineering applications (see www.laser-focusworld.com/articles/362152). Unfortunately, use of a mouse or standard joystick does not let the operator know what force is being exerted, and more-sophisticated force-feedback methods such as haptic guidance (see www.laserfocusworld.com/articles/355179)--using an artificial force field--are in their infancy. Recognizing that optical tweezers can also be used for force measurements, the research team seized on the opportunity to use the actual forces acting on a bead (measuring the magnitudes of the forces by analyzing images from a high-speed video camera), and coupled those force measurements to a low-cost commercial haptic interface--the Falcon by Novint (Albuquerque, NM).