# Laser Tweezer

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## Introduction: Laser Tweezer

First of all,

I gonna use a <30mW Laser, to not burn your eyes use Laser-safety-goggles and become sure no one get harmed by your actions. While working on the tweezer it's safer not to wear an metallic or reflective stuff and use anodized tools.

A few more details on this development, I have built up that construction in recent weeks at the University of Tübingen for the beginner training in physics. This structure will cost quite a lot of money but who can afford it will surely have a lot of fun with it.
In this structure, polystyrene beads are used as colloids. Since the diameter is much larger than the wavelength of the laser I will add only the geometric explanation of optical tweezers.

The distances between the individual optical elements are only of secondary importance. But I will explain every part of what is important in the beam path as the laser beam and look lost.

I know this instruction is not very good but with your help and some time it will be helpfull.

### Teacher Notes

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## Step 1: Adjust the Laser

You should see a center laser dot on all your lenses and especially on the objective lens.
And a center dot at your ccd-image.  To achieve this, use two of the three mirrors. The second mirror is set piece by piece so that you can see a central point on the CCD. Then, the first mirror is adjusted so that the aserstrahl objetive re-center hits. I have achieved the best results when I've adjusted the levels simultaneous with two hands

## Step 2: In Action

Participated in the
Wicked Lasers Contest

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## 10 Discussions

anymore progress on this? The prism cube is a beam splitting (recombining) cube.

Also to improve the video you could do with some light on the sample and possibly a filter to block the laser to you ccd then you can watch the particles 'jump' into the trap

Its seems he's building 'optical tweezers'. Using lasers its possible to precisely move individual atoms, which is an incredible thing to be able to do, normally this is done using very expensive equipment in universities or laboratories.

This build is meant for moving microscopic dielectric objects.

what is/are microscopic dielectric objects????

Cool setup and looks like something out of the TV show, big bang theory..... but have no clue what your goal is.....

I am totaly sorry, i didn't have to be a dieletric objekt this ist just for the case that the diameter oft the particel ist smaller or equal to the wavelenght. But a dielectric is an insulator under normal circumstances and can be polarized by an electric field.

In our case d>\lamda we just need a transperent particel.

This is pretty amazing, I hope you get this finished, and possibly a demonstration video!

I am aware that this guide is not complete yet, but I'll work on this and like to include your suggestions. I will upload a video once the colloids are there. Also I would like to write an introductory theory.

This is a really cool project! It's hard for me to judge whether it works or not, because there isn't enough detail on the actual assembly for someone to repeat the build. Having some information on the distances and heights of the components would help. So would a bit of guidance for non-experts on how to safely do optical alignment.

In your introduction, it would be very useful to provide some of the theory and purpose behind optical tweezers. Explain a bit about why they are used, how they work (in particular the focusing waist), and how to control them. Then start with Step 1 on the materials and assembly instructions.

In your final step, it would be really great if you able to connect a small video camera to your microscope, and upload a few pictures showing your tweezers in action.

The two drawings you've included are annotated in German. Because they are images, rather than text, users cannot easily run them through online translators. Could you provide in the text a translation to English of the terms involved, or a more detailed explanation of the drawings, for the many readers who are not already familar with the science?

A small note about terminology. In American English, the term "breadboard" refers to an electronic protoyping unit, with many holes spaced at 0.1-inch (2.54 mm) intervals and electrically connected. I believe that you are refering to an optical bench or optical table for this project.