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Portable Optical Tweezers Educational Kit

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Portable Optical Tweezers Educational Kit




  • Designed for Educational, Demonstration, and Classroom Use
  • Easy-to-Use Kit Includes All Components Plus Educational Materials

Optical Tweezers Educational Kit

  • Designed for Educational, Demonstration, and Classroom Use
  • Complete Kit Includes All Hardware and Tools (Computer Not Included)
  • Includes Extensive Manual for Easy Assembly and Use
  • Choose from Kits Containing Imperial or Metric Components

Kit Details

  • Optical Tweezers Kit
  • Portable without Readjustment
  • Visible Trapping Laser
  • Imperial or Metric Versions Available

Optical tweezers, also known as optical traps, move and manipulate small particles using only a beam of light. A focused laser beam is used to exert forces on electrically uncharged particles with sizes from 1 to 10 µm, allowing the particles to be trapped, moved, and manipulated. This optical tweezers kit is optimized for classroom and lab use. It features an easy-to-construct optical path and sample positioning stage, a visible laser source, and a camera system for easy demonstration. The kit is assembled on a 30 cm x 60 cm (1' x 2') aluminum optical breadboard (included) and can be easily moved for demonstration purposes without needing realignment.

We also offer a highly configurable modular optical tweezers system for research and advanced graduate laboratories.

Thorlabs Educational Products

Thorlabs' educational line of products aims to promote physics, optics, and photonics by covering many classic experiments, as well as emerging fields of research. Each kit includes all the necessary components and a manual that contains both detailed setup instructions and extensive teaching materials. These kits are being offered at the price of the included components, with the educational materials offered for free.

 

Thorlabs demonstration/educational optical tweezers kit is designed for classroom, lab, and other educational uses. It features a visible laser light source and an objective that does not require oil immersion. The CMOS viewing camera can be connected to a PC for demonstration use. The entire system is mounted on a 30 cm x 60 cm (1' x 2') aluminum breadboard and can be easily moved without needing realignment.

Laser and Microscope System

The EDU-OT1(/M) kit uses a L658P040 658 nm laser diode as the trap laser source. This 40 mW visible laser allows the spot to be easily observed through the microscope during operation for intuitive classroom demonstrations. The laser is focused through a Zeiss 63X, 0.8 NA objective, which also serves as the objective for the microscope. Sample illumination is accomplished using an MCWHL5 white LED, and the sample is viewed through a Thorlabs DCC1645C color CMOS camera. The laser, microscope, and optical path of the optical tweezers kit are shown below to the left.

Sample Positioning System

Samples are placed on the 3-axis sample positioning stage and moved around the static laser beam during experiments. The stage consists of two motorized MT1-Z8 (MT1/M-Z8) 12 mm travel translation stages for X- and Y-axis travel, plus a manual MT1 (MT1/M) stage for Z-axis translation. The motorized stages are controlled by TDC001 servo motor controllers, each of which features a 1-axis actuator with customizable velocity settings. The sample positioning stage is shown below to the right.

 

Optical Tweezers Operation

Optical traps can be characterized by two essential forces: the scattering force and the gradient force. The scattering force can be attributed to the principle of radiation pressure. Since the incoming laser light is partly absorbed and/or reflected by the particles, a momentum transfer occurs, which makes the particles move away from the light source. Thus, the scattering force increases with the laser power.

The second, more important force is the gradient force. If the laser beam acts on particles with a higher refractive index than the aqueous medium in which they are dispersed, they travel in the direction of maximal light intensity, allowing the particles to be trapped in the laser focus. If the laser is tightly focused, the gradient force can exceed the scattering force so that the particles can be trapped and moved in all three spatial directions.

For experimental purposes, microscopic glass or plastic beads (about 1 to 10 µm) or various other objects are dispersed in liquid (water, alcohol) on a glass slide. The particles can then be moved and manipulated by trapping them in the focused laser beam and moving the slide, which is attached to a positioning stage. The objective, CMOS camera, and an additional tube lens compose a microscope, which allows for the observation of the trapping procedure on the PC monitor. Various experiments can be performed with this setup, including trapping of particles with varying laser powers (up to 40 mW), evaluation of the effective viscosity of the dispersion via Brownian motion, determination of the optical trapping forces and their harmonic potential, and statistical analysis of the probability of presence of the particles in the trap.

 

 

Several experiments that students can undertake as part of a lab course are outlined below. In addition to these exercises, the manual contains instructions for more activities such as adjusting the setup, finding the correct focus plane for the camera and laser, and arranging trapped particles within a sample.

Sample Preparation

Samples for the optical tweers kit are simple to prepare. A sample containing 1 µm or 3 µm polystyrene beads is useful, as these are well-suited for getting to know the operation and handling of the optical tweezers. Alternatively, an emulsion of cream in water will also produce particles that can be captured with the optical tweezers kit.

The following materials are necessary to create the sample:

  • Microscope Slide with 20 µm Deep Wells
  • Cover Glass
  • Watch Glass Dish
  • Pipette
  • Sample Solution:
    • Solution with Polystyrene Beads (PS) and Distilled Water
    • Cream and Water Emulsion

First, place a drop of the solution with the PS beads in the watch glass dish and combine with sufficient distilled water. Place this mixture in a well on the microscope slide using a pipette. Put a cover glass over the sample so that there are no air bubbles between the glass and the sample.

The samples can either be prepared before each experiment or they can be sealed between the slide and the coverglass with a UV adhesive. We recommend allowing students to prepare new samples as an educational exercise.

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