DIY spectrometer

August 30, 2012 at 1:44 pm | | hardware, science@home, wild web

A Kickstarter project is aiming to make a kit for simple DIY spectroscopy. For spectra-nerds, this is pretty cool.

(Hat tip Austin.)

more lytro pics of lasers

March 21, 2012 at 3:25 pm | | hardware

(Other photos here.)

An optical parametric oscillator and related optics:


refocusable images of microscope and laser table

March 21, 2012 at 2:51 pm | | hardware

I bought a Lytro camera, which captures the entire depth of field and allows you to refocus a picture after you take it. It accomplishes this by having a microlens array in front of the sensor, which captures information about light rays and angles in the entire field, then the image can be reconstructed in post-processing.

Here are some shots of microscopes and laser tables. Click around on the images to refocus.

More photos here.

P.S. Sorry I’ve been so absent. Postdoc+baby = no time for blog. :)

playstation joystick control on electron microscope

July 13, 2011 at 11:13 am | | hardware, nerd, stupid technology

Fancy electron microscope…


…uses a game controller to manipulate the internal robots. Ha!

why is the left bike pedal left-hand threaded?

April 18, 2011 at 10:06 am | | hardware, science@home

Any cyclist knows that the left bike pedal is left-hand (i.e. reverse) threaded. This is so the pedal doesn’t unscrew itself while you’re pedaling. But go grab a bike and spin the pedal and crank around and you might be a little confused. Last time I did this, I thought, Wait why isn’t the right pedal reverse threaded? When you spin the pedal and crank forward, as if you’re actually powering the bike, the effective spinning of the pedal around its axle (AKA the spindle) should actually unscrew both pedals: lefty-loosey on the right pedal and righty-loosey on the left. Did every bike manufacturer get this wrong?!?

Of course not, and the real answer blew my mind. (Probably because I’m not a mechanical engineer.)

It is not, not mind you, because of the effective unscrewing force from the non-zero friction of the ball bearings. Instead, it is an effect that works in the opposite direction (in this case): mechanical precession:

“Precession is the process of a round part in a round hole rotating with respect to that hole because of clearance between them and a radial force on the part that changes direction. The direction of rotation of the inner part is opposite to the direction of rotation of the radial force.”

The source of the screwing/unscrewing force is thus radial on the spindle—the downward force you put on the pedal—instead of the twisting force from the ball bearing friction. This radial force translates into a screwing/unscrewing force because there is a small amount of clearance between the spindle and the threaded hole in the crank. I picture it like a pencil in a toilet-paper tube: crank the end of the pencil around, and there is a force that wants it to rotate on its long axis (from friction with the wall of the tube).

The screwing force from precession (on a reverse-thread on the right pedal) is much stronger than the unscrewing force from friction of ball bearings, so bike manufacturers ignore the latter.

I wish I could find an animated gif of mechanical precession, but I haven’t found one. Anyone have a book on “advanced thread theory” and want to make an animation?

UPDATE: Here’s a nice animated figure from Wikipedia:


Animation of mechanical precession” by Chris ShannonOwn work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

what your laser pointer says about you

March 10, 2011 at 4:50 pm | | conferences, hardware, nerd, science community

Red: You either don’t really care if anyone can see what you’re pointing at or you’re cheap and you use the free pointer you got from a vendor at the expo. Of course, you could be one of those considerate folks who buy very bright red pointers, because you stubbornly like what red looks like even though human eyes are not sensitive to 633 nm. That’s fine.

Green: You want your audience to see what you’re pointing at. Unless you bought a 5+ mW laser (either because you’re showing off or because you didn’t realize how sensitive the human eye is to 532 and bought the brightest laser you could find). In that case, you’re blinding your audience. If you’re going to get a 5 mW laser, get it in red. That’s classy and visible!

Blue: You’re a bad-ass. You don’t care that blue lasers are more expensive and slightly harder to see, you want the audience to know that you’re a real laser jock. (Or maybe you’re worried about leaking 1064 nm from green laser pointers.)

Purple: You’re so bad-ass you’re crazy. You don’t care that the human eye can hardly detect and can’t focus on 405 nm. You want to show that you support Blu-ray.

Yellow: You think blue lasers are soooooo 2009.

Invisible: You have a UV or IR laser pointer? Maybe a tripled or undoubled Nd:YAG? You’re nuts.

Maser pointer: I want one.

Inappropriate Labware

May 31, 2010 at 9:38 pm | | hardware, science and the public

We have these Al bases floating all over the place.  I guess when Stanford sanitized their mascot, we never got around to PCing our opto-mechanics.

Hg Thermometry

November 24, 2009 at 1:01 am | | hardware, stupid technology

In keeping with green traditions, we’re required to trade out Hg containing thermometers.  For those cases where no equivalent alcohol thermometers exist, they supply Hg thermometers that are encased in Teflon.  One of those thermometers was my baby, a 1/2 degree with a ground glass joint that goes with my favourite distillation head, range 0 to 400C.  Except that Teflon melts at ~325C.  I discovered this fact when the teflon melted off the thermometer and into my rb during a distillation.  FMC (Fail My Chemistry).

auto hammer

May 18, 2009 at 8:28 am | | hardware

I just saw a commercial for Craftsman’s automatic hammer. I thought that was a pretty cool gadget. Good for tight spaces (although it doesn’t sound like it’s powerful enough for serious nails).

Here’s a video of it in action.

review of the NanoDrop 2000c

May 11, 2009 at 12:04 pm | | hardware

Our lab recently bought a NanoDrop 2000c spectrometer. It sure is cute:


Just look at it next to our old Perkin-Elmer Lambda-19 spectrometer:


(Although, that’s not really a fair comparison, because the Lambda-19 is a real spectrometer, with high sensitivity and resolution.)

The ND 2000c has a small pedestal with a fiber at the base; onto said pedestal, a research may place 2-5 uL (or even less!) solution and the dang machine measures the absorbance! The pedestal has a mechanism to move up and down in order to change the pathlength (the solution forms a small column between the pedestal and anther fiber above it). Very cool. The detector is a linear CCD array, so no scanning: hit go and a second later a spectrum pops up on the screen.

Of course, the sensitivity of the detector is less than that of our old real spectrometer, and the resolution is set by the CCD array—I don’t think the grating or most other parts inside move. But, with a high enough concentration, you can get quick-and-dirty spectra that actually look pretty good.

The ND 2000c also has an extra measuring mode, because it has a cuvette holder. Click a few buttons and the spectrometer measures the solution in a standard 1-cm cuvette (or, of course, small-volume or short-pathlength cuvettes, but why would you when you have the cool pedestal mode?). The cuvette holder also has a stirplate and heater, so you can measure biological samples or run reactions. Same issue with sensitivity and resolution, but I was able to get some usable spectra of a chromophore by using high enough concentrations and tweaking some settings:


Ignore the changes in the shape of the peak as the concentration increases (that is from different ratios of ethanol and water in the mixture). The higher-concentration samples produce spectra that are publishable; low-concentration samples are probably too noisy and low-resolution to pass as publishable spectra. Nevertheless, the repeatability even at low concentration is acceptable.

My biggest complaint so far is the software. Of course, this may be because I am learning a new interface after five years of using the Lambda-19, but I find the ND 2000c software confusing, limiting, and sometimes buggy.

For example, a user cannot directly change the integration time in order to better measure low-concentration samples. Instead, the software automatically sets the integration time for each run based on the amount of light incident on the detector. This is probably a good thing, because it prevents a user from inadvertently overexposing and damaging the CCD; but it’s still kind of annoying. Fortunately, the tech reps helped me by explaining how to set a wavelength range just around the peak of interest (i.e. not UV peaks), so the integration time resets to best measure that peak. (If I had not done that in the spectra above, they would have looked really crappy!)

The customer and tech service has been awesome so far. When I was thinking about buying the ND 2000c, the sales rep sent me sample spectra and answers a lot of my questions. Now that we have the spectrometer, I’ve communicated with two of the tech reps on the phone and via email and they’ve helped me with some the tricks and tips of using the software.

Snuggie Scientific

April 24, 2009 at 8:53 am | | hardware, stupid technology, wild web

Want to not die while working in the lab?  Lab coats are okay, but they don’t show off your awesome ass.  And the second you need to reach for something, you catch on fire.  But now there’s the Snuggie Scientific, from the makers of Snuggie.  It’s a blanket and a PPE.

Now you can titrate without feeling cold.  Run a column and feel slightly less cold.  Check the New York Times and feel slightly less cold.  Make coffee.  Drink coffee, all without ever having to feel the icy pinch of 72 degrees.

Made from space age materials that are totally not soluble in every single liquid you handle, the Snuggie Scientific lets you work alone without ever being alone.  And that’s why I wear one too.


nuclear duct tape not so hot?

February 23, 2009 at 1:18 pm | | hardware, wild web

Geekologie and elsewhere reported that 3M sells nuclear-grade duct tape, which is true.

But not everybody is satisfied with the tape.


I guess you can’t please everybody.

make your science sexy

January 7, 2009 at 7:15 pm | | crazy figure contest, hardware, literature, science and the public, science@home

This machine is the closest some graduate students get to the Real Thing:


“Finally, theories proposed for the mechanism of breakage were investigated on a laboratory coital model.”

Source: White, N.; Hill, D.; Bodemeier, S. Male condoms that break in use do so mostly by a “blunt puncture” mechanism. Contraception 2008, 77, 360-365. (Also reported in Nature’s news section here.)

electronics cleanup

December 19, 2008 at 2:27 pm | | everyday science, grad life, great finds, hardware

We needed to move several pieces of electronic equipment from a table because they were “blocking” some circuit-breaker boxes. So we discarded of all the spare monitors that were stored under laser tables to make room for the no homeless equipment:


In the process, we found some desiccated rats. W.E. found one that had a frikkin’ wasp nest growing inside it.


Weird. And very gross.

No one buys a damn $8000 oscilloscope for Christmas

December 18, 2008 at 10:44 am | | hardware, science and the public

Why, I ask you, does it seem that every vendor I’ve even thought about soliciting a quote from has decided to flood my email with “Holiday Specials” on highly specialized scientific equipment? There’s a reason that O. Henry tells not of Jim selling his oscilloscope to buy Della a phototube cryocooler, while Della sells her monochromator to buy Jim a signal generator. That reason is because it’s moronic.

Why don't you love me?
A little subtle sexism, anyone?
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