Microfluidics: Miniature Chemistry Labs

enkidu writes: "The NYTimes has a story (free reg, yaba yaba) about the rapidly emerging field of microfluidics and describes some of the methods used in making micro-valves, pumps and other components. In the future, you won't need to send your blood/urine sample to a lab, your doctor will put in his "lab-in-a-box" and hand you a printout before your leave."

Comments

But the insurance companies won't allow it...

[printman]

A lot of doctors ran out an bought their own mini-lab test equipment when it first came out. Not only did it cost them less than sending it out to be processed, but they got results faster.

*However*, the insurance companies have put a stop to that. My doctor has to send out my bloodwork and wait almost a week to check my cholesterol, instead of using his own equipment and getting me an answer within an hour or so... In the process, I end up paying *more* to my insurance company and they get to negotiate mass-quantity lab work with the lowest bidder.

Re:But the insurance companies won't allow it...

[cplmd]

As a physician, it's not just the insurance companies to blame - if fact not them at all. It's how our wonderful federal government responds to a few of my unscrupulous colleagues.
Specifically, Rep. Pete Stark in his three versions of Stark Acts have reduced how much a physician can do for you. Pharmacies, labs and x-ray cannot be owned or used by the doctor if he does have an interest in the facility. I don't have a problem with that given the kickbacks a few doctors got in the past.
However, as always with federal regulation of individual/local problems, it has extended into areas that no longer make sense and actually make it worse for you as a patient. This office-lab in a box being a case in point.
While on my soap box, it would be nice if the federal government limited and regulated the legal, esp. civil court system as much as the medical one. Given spiraling malpractice insurance costs and the actual closure of some rural hospitals due to legal liability and insurance costs, maybe as the federal government did with medicare/medicad in setting limits on what reimbursement would be to doctors and hospitals for a given disease, lawyers in this country should be limited in what they are paid for say a divorce, murder defense or malpractice / workman's comp. case.

Daily drug screenings! Yay!

[13013dobbs]

*sigh* Now it will be easier for employers/cops/whoever to scan people for evil drugs.

Obligatory no-reg link

[no parity]

http://college.nytimes.com/2002/01/01/science/phys ical/01MICR.html

On the hardware side...

[danamania]

I wonder if this could be a useful thing in cooling circuitry such as CPU's. Build a cooling system into the CPU itself. perhaps an ultra-efficient heatsink which pumps liquids through tiny channels in thin fins - anything to help heat dissipation.

...or combine the medical side of it and pump your own body fluids through your cpu - ooah. scary.

Re:On the hardware side...

[rgmoore]

Unlikely. The flow that you can get through a very small channel is absolutely tiny. Over a large range, the backpressure goes up as one over the square of cross-sectional area, so a large array of small channels can allow substantially less flow at a given pressure drop than a single large channel of the same area. Using channels the size that you can make using this kind of process you simply aren't going to be able to get enough flow to make much difference.

(BTW, I do have some idea of what I'm talking about; I've worked in microfluidics and still work in a closely related field.)

Re:On the hardware side...

[deglr6328]

"...or combine the medical side of it and pump your own body fluids through your cpu - ooah. scary."

'OH NO! He's crashing!.. Code Blue!'

takes on brand new meanings!

Won't this hurt accuracy?

[diamond0]

Due to the small samples such a machine would process, the error margin is bound to be huge. This is elementary statistics, folks; if you want milligrams per deciliter of blood cholesterol, or any sort of statistic about a body fluid, the more of a sample available to the process, the more accurate it's going to be. Compare this to Nielsen surveying only twenty people, or Gallup only a hundred.

I've been wrong before; maybe a biochemist could chime in and let us know how much blood or urine constitutes a true statistical sample?

Re:Won't this hurt accuracy?

[baz00f]

Speaking as a pedigreed biochemist, you are correct in the extreme of vanishingly small samples. But these devices are still working with enough volume such that an analyte of interest at a substantial concentration (glucose, cholesterol, etc.) is effectively present at the same concentration at nearly all sample volumes.

Things DO fall apart (as you intuit) when the concentration of the analyte gets vanishingly small. We see this routinely when we try to quanitate DNA using PCR (Polymerase Chain Reaction) methods. PCR is sensitive enough that we can detect ONE copy of a DNA molecule in a volume of sample. So if you have say, one copy in 1ml of volume, and you sample .1 ml and do your PCR, your test would come up negative upon repeats (on average) 9 out of 10 times. With small numbers of copies you can use Poisson statistics to calculate your hit rate. With higher concentrations your Poisson distribution collapses to a gaussian that gets narrower and narrower, which is the regime that most normal wet analytical techniques work. For example, fasting blood glucose is about 100 mg/dl, which is about 5 mM. Assuming your device can work with 1 nanoliter sample size (this is about 100x smaller than a volume about the size of the proverbial period at the end of a sentence) you would have 3x10^12 molecules of glucose in it. Assuming your technique is sensitive enough to register the presence of this "small" number of molecules, you are still far away from seeing sampling errors on repeats of the same sample due to random fluctuations of the number of molecules (the "concentration") in any given sample.

Paul Yager at U. Washington (Seattle) has a good introduction to microfluidics:

Microfluidics Tutorial and Prognostication

Re:Won't this hurt accuracy?

[danamania]

I posed this question to a friend who does work with testing body fluids in a lab, and her response was that since there -are- minimum sample sizes, one small test on a tiny scale could certainly have errors on a different scale to current tests.

My guess is by looking at the relative complexity (in number of components) of the pumps/mixers/detectors compared with a several hundred million transistor CPU, that an array of perhaps millions of separate testers could be easily built, one which would run millions of simultaneous tests.

Only comparing those results with known working ones would show if the results were comparable - certainly one more type of testing can't hurt, and if it only proves extra accuracy in a few cases, they may be ones with a great impact.

Re:Won't this hurt accuracy?

[Vinson Massif]

Analytical volumes are in the mL range to ease handling and to minimize cumulative error. In most modern techniques, microlitres are taken up by the test instruments; the actual amount of 'stuff' that is actually analysed is minute. Good test design and bench technique give good results.

It's not the sample volume I'd be questioning, but calibration, standarization, and QA procedures. These are the root of inaccurate (and imprecise) test results.

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Great news...

[cperciva]

next time my doctor needs to take a blood sample maybe they'll be able to take a small enough quantity of blood that I won't faint. It's not a problem if they only need to run one test, but when they need four or five tests this will be a major improvement.

Dr. Quake

[Tsar]

It's interesting to see Dr. Stephen R. Quake's name cropping up again in one of these stories. His group is working on some amazing stuff, mostly working with one molecule at a time—although, admittedly, they're moby molecules.

No, I wasn't going to comment on his framerate.