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Optical Tweezers

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Re: Optical Tweezers

#11

Post by scrumbledober »

matthberg wrote: post #9
sleavey wrote: post #6

As an undergrad I worked in a lab where they built an iPad app to control optical tweezers [1, 2]. It's a cool example of the possibilities of this technique - allowing you to manipulate nanoscopic particles suspended in fluid. [1] https://www.youtube.com/watch?v=qgDMcP9e5G0 [2] http://iopscience.iop.org/article/10.1088/2040-8978/13/4/044...

Pardon my language yet that is so fucking cool. Do you know how the app interfaced with the microscope and optical tweezers? I just love the idea of a simple api that controls this crazy complicated lab equipment.

I remember as a child watching an episode of some version of battlebots, where a competitor had an articulated grabbing arm on top of his robot. The arm had, I believe, two articulating joints and then an articulating grabber/jaw at the end. To control the arm he had made a small 2d model of it and could simply move that around on a clipboard like backing, and it would map those movements to the servos in the arm. I was blown away by how intuitive and simple of an interface he had made for this contraption that I imagined would work with a complicated series of levers similar to those used by backhoe operators. I credit this in no small way with inspiring my ever-persistent need to automate as much as possible in my adult life.

EDIT: If anyone has any idea which episode of what show this was, I would be very excited to watch it again

Re: Optical Tweezers

#12

Post by apo »

arctux wrote: post #5

I'm a grad student in a lab that specializes in using optical tweezers for single-molecule biophysics research. I'm out sick today with nothing better to do, so feel free to ask me anything.

Reading that these tweezer beams are focused with a microscope objective raises the question of how much energy is in one of these beams.

For example, what would happen if the tip of the beam made contact with a piece of paper, steel, etc.?

Also, what precautions, if any, need to be taken to get air out of the system you use these in? If vacuum, how much?

Re: Optical Tweezers

#13

Post by Jun8 »

arctux wrote: post #5

I'm a grad student in a lab that specializes in using optical tweezers for single-molecule biophysics research. I'm out sick today with nothing better to do, so feel free to ask me anything.

Would it be possible to build your own, e.g. something like the one shown here: https://www.youtube.com/watch?time_continue=104&v=Sq7GaO8iqu...?

Re: Optical Tweezers

#14

Post by dekhn »

This isn't the first Nobel for optical tweezers. Steve Chu used them in atom trapping experiments at Bell Labs, although the award is for the atom trap results, not for the tweezers themselves.

Re: Optical Tweezers

#15

Post by arctux »

apo wrote: post #12
arctux wrote: post #5

I'm a grad student in a lab that specializes in using optical tweezers for single-molecule biophysics research. I'm out sick today with nothing better to do, so feel free to ask me anything.

Reading that these tweezer beams are focused with a microscope objective raises the question of how much energy is in one of these beams. For example, what would happen if the tip of the beam made contact with a piece of paper, steel, etc.? Also, what precautions, if any, need to be taken to get air out of the system you use these in? If vacuum, how much?

Our strongest trap is powered by 1.5 W 1064 nm laser beam. (For comparison, laser pointers are usually under 0.005 W.) Unlike most other light sources, laser power measures the output power rather than electrical input power.

The beam will instantly ignite paper, and will cause damage to the most common type of laboratory laser beam blocks, which are made out of stainless steel.

We don't take the air out the system. Air is basically completely transparent in the visible and infrared. We sometimes flood a portion of the instrument with helium, since its index of refraction is ten-fold closer to 1 than air's. This causes the beam to fluctuate less due to air movement.

Re: Optical Tweezers

#16

Post by arctux »

Jun8 wrote: post #13
arctux wrote: post #5

I'm a grad student in a lab that specializes in using optical tweezers for single-molecule biophysics research. I'm out sick today with nothing better to do, so feel free to ask me anything.

Would it be possible to build your own, e.g. something like the one shown here: https://www.youtube.com/watch?time_continue=104&v=Sq7GaO8iqu... ?

Yes, but high-power lasers need to be treated with respect. Reflections are capable of instantly and irreversibly blinding. There's an overused joke in labs that work with them: "do not look into laser with remaining eye".

If you're going to attempt to build one, please get a pair of laser glasses that are rated for the wavelength you are using.

Re: Optical Tweezers

#17

Post by mikey_p »

arctux wrote: post #16
Jun8 wrote: post #13

Earlier quoted context omitted.

Would it be possible to build your own, e.g. something like the one shown here: https://www.youtube.com/watch?time_continue=104&v=Sq7GaO8iqu... ?

Yes, but high-power lasers need to be treated with respect. Reflections are capable of instantly and irreversibly blinding. There's an overused joke in labs that work with them: "do not look into laser with remaining eye". If you're going to attempt to build one, please get a pair of laser glasses that are rated for the wavelength you are using.

Spent alot of time working with low to medium power lasers in the entertainment industry, and I'm happy to say that was also a joke in that industry as well.

Re: Optical Tweezers

#18

Post by arctux »

dekhn wrote: post #14

This isn't the first Nobel for optical tweezers. Steve Chu used them in atom trapping experiments at Bell Labs, although the award is for the atom trap results, not for the tweezers themselves.

Chu's prize was for laser cooling, which uses a magneto-optical trap. Magneto-optical traps confine atoms by exploiting the Zeeman effect, a spatially-varying magnetic field, and a laser with a precisely-controlled wavelength tuned to be slightly red of an electronic transition. Optical traps, on the other hand, rely on the refraction of a much larger, but still microscopic, object.

Some of Chu's work uses an optical trap, but that work did not earn his prize.

Re: Optical Tweezers

#19

Post by arctux »

mikey_p wrote: post #17
arctux wrote: post #16

Earlier quoted context omitted.

Yes, but high-power lasers need to be treated with respect. Reflections are capable of instantly and irreversibly blinding. There's an overused joke in labs that work with them: "do not look into laser with remaining eye". If you're going to attempt to build one, please get a pair of laser glasses that are rated for the wavelength you are using.

Spent alot of time working with low to medium power lasers in the entertainment industry, and I'm happy to say that was also a joke in that industry as well.

Powerful lasers can be scary, especially if they're in the infrared. The first warning you receive that it's reflecting into your eye is blood seeping into the vitreous humor from your retina's capillaries.

Re: Optical Tweezers

#20

Post by crispyambulance »

arctux wrote: post #15
apo wrote: post #12

Earlier quoted context omitted.

Reading that these tweezer beams are focused with a microscope objective raises the question of how much energy is in one of these beams. For example, what would happen if the tip of the beam made contact with a piece of paper, steel, etc.? Also, what precautions, if any, need to be taken to get air out of the system you use these in? If vacuum, how much?

Our strongest trap is powered by 1.5 W 1064 nm laser beam. (For comparison, laser pointers are usually under 0.005 W.) Unlike most other light sources, laser power measures the output power rather than electrical input power. The beam will instantly ignite paper, and will cause damage to the most common type of laboratory laser beam blocks, which are made out of stainless steel. We don't take the air out the system.…

    > specializes in using optical tweezers for single-molecule biophysics research.
... > The beam will instantly ignite paper, and will cause damage to...

Curious, it appears that you guys use a highly focused beam on small particles, like 1 W focused into a diffraction limited spot, right?

How come the bio-molecules that you're manipulating with this light don't just "burn up"? Is it because they're mostly transparent at that wavelength? Or you're only exciting a marker molecule that is stuck to them?

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