home-made plasma cleaner

July 23, 2014 at 12:52 pm | | everyday science, hardware, science@home, stupid technology

I really want a plasma cleaner, for cleaning coverslips and activating glass for PDMS bonding, but they cost thousands of dollars. I thought that was a lot of money for a glorified microwave. So I made my own.

Drill a few holes in glass:

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Make a PDMS seal (thanks Kate):

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Glue the chamber:

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We’re ready to go!

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Fill the chamber with argon, evacuate it, turn on the microwave oven, and … voila! … a plasma:

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Below are slides before and after (right) plasma treatment. You can see the contact angle of water is dramatically reduced.

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It works!

Well, not really. I found that the plasma really only stays lit with argon. When I flow air in, it extinguishes, but also burns some of the rubber hoses. That adds more dirt to my slides than I want.

Conclusion: don’t do this at home. :)

(Well, that might be a little harsh. It does work well to bond PDMS to glass. And I’ll try a longer etch sometime to see if it will ever clean the coverslips.)

checklist of unusual phenomena

July 22, 2014 at 1:40 pm | | nerd, stupid technology

AKA “troubleshooting.”


eyepiece laser safety filter and 3D printing

July 8, 2014 at 3:57 pm | | hardware, lab safety

With TIRF and lasers on many fluorescence microscopes these days, there’s a huge risk of seriously damaging your vision. Not so much from a stray beam (which is probably diffuse or your blink reflex will be faster than the damage threshold), but more from looking in the eyepiece without the proper filters in place. A reflected laser beam focused with the eyepiece lenses right onto your retinas can be vary damaging.

(That happened a Berkeley a few years ago, and EH&S asked everyone to take the eyepieces off their TIRF scopes. I removed one, so that you’d only lose one eye.)

Interlocks between your scope port setting and your laser is one option. But that means you can’t ever look at your sample with your eyes (at least the fluorescence). The elegant solution it to put a multi-band emission filter in your eyepiece tube to block any laser light:

eyepiece laser safety

I got this idea from Kurt, who even designed a filter holder that you can 3D print. I modified that part for one that would fit in our Nikon TE2000.

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I also printed some other parts for our TE2000. After we upgraded our epi illumination source from a Hg lamp to a Lumencor Spectra-X LED, we no longer needed the ND filter sliders on the illuminator tube, because the LED intensity is easily controlled by software. I’ve always hated those sliders, because they are easy to accidentally knock into the wrong position. That, and they aren’t encoded into the image metadata, so you have no idea what slider settings you had when you look at an image 3 months later!

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So I removed the ND sliders and replaced them with a nice plug to block the light.

I have my 3D designs on the NIH 3D Print Exchange.

thorlabs lab snacks boxes for arduino enclosure

July 3, 2014 at 7:38 pm | | everyday science, hardware

On the topic of hardware syncing, I figured I should boast about my very fancy Arduino enclosure. I used a Thorlabs Lab Snacks box (one of the Great Boxes of Science):

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Of course, Nico makes beautiful laser-cut boxes for his Arduino, and Kurt has a nice 3D-printed box. But I think I’ll stick to this reduce/reuse/recycle approach. :)

UPDATE: I guess I’m not the only one. Labrigger posted a similar pic!

UPDATE 2: I made a bigger one to fit two Arduinos:

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