Haptic Optical Tweezers Let Us ‘Feel’ Microstructures

PARIS, Sept. 16, 2013 — A new technology called haptic optical tweezers allows microscope users to manipulate samples by sight and touch, which could improve dexterity of micromanipulation and microassembly.

The tweezers “will become an invaluable tool for force feedback micromanipulation of biological samples and nano- and microassembly parts,” said Dr. Cécile Pacoret of Université Pierre et Marie Curie (UPMC), a co-author of the study.

A representation of the micromanipulation experimental setup with the haptic optical tweezers, enabling cell exploration and more. Courtesy of Pacoret/UPMC.

Designing optical tweezers to incorporate high-quality touch-based feedback is challenging, given the requirements for very high sensitivity and dynamic stability. A big challenge was to sense and magnify piconewton-scale forces enough that human operators could perceive interactions they had never experienced before: adhesion phenomena, extremely low inertia and high-frequency dynamics of extremely small objects such as Brownian motion.

The ability to use touch as a tool will allow exploration, diagnosis and assembly of various types of elements — from sensors and microsystems to biomedical elements including cells, bacteria, viruses and proteins. These objects are fragile, and their dimensions make them difficult to see under a microscope. If this tool can restore the sense of touch under microscopic operation, it will not only help efficiency but also expand scientific creativity, Pacoret said. "This tool will offer a new degree of freedom and accessibility to researchers, providing, for example, new versatility for the study and micromanipulation of cells.”

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The research required a mix of different experimental techniques and theoretical knowledge. The Institute for Intelligent Systems and Robotics, a lab belonging to UPMC and the National Center for Scientific Research, is skilled in both microrobotics and haptics, but the investigators realized as the project progressed that they needed additional expertise in optics and vision, which was available at UPMC. “This project would not have been possible without this multidisciplinary environment and additional collaboration of the international optical tweezers community,” Pacoret said. “The high level of interdisciplinary cooperation is what made this project unique and contributed to its success.”

The work appears in Review of Scientific Instruments.

For more information, visit: www.upmc.fr

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Published: September 2013

Glossary

microscope: An instrument consisting essentially of a tube 160 mm long, with an objective lens at the distant end and an eyepiece at the near end. The objective forms a real aerial image of the object in the focal plane of the eyepiece where it is observed by the eye. The overall magnifying power is equal to the linear magnification of the objective multiplied by the magnifying power of the eyepiece. The eyepiece can be replaced by a film to photograph the primary image, or a positive or negative relay...
optical tweezers: Optical tweezers refer to a scientific instrument that uses the pressure of laser light to trap and manipulate microscopic objects, such as particles or biological cells, in three dimensions. This technique relies on the momentum transfer of photons from the laser beam to the trapped objects, creating a stable trapping potential. Optical tweezers are widely used in physics, biology, and nanotechnology for studying and manipulating tiny structures at the microscale and nanoscale levels. Key...

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