Simple Engineering: A Centrifuge and a Microscope for less than $3!

Frequently the simplest method of doing things turns out to be the most efficient. In science and engineering, sometimes there is the tendency to think too deep or explore too much on things that have a simple solution.

Running a test for the varieties of samples such as cell cultures, urine and blood require the ability to isolate pathogens or DNA which will help identify the cause of the disease or ailment.

The process requires the use of a centrifuge. Centrifuges are important in a test. For instance, in a blood testing, the blood is a composite made up of clear solution, plasma (55% of total volume), leukocytes (white blood cell) and platelets which forms less than 1% of the total blood volume and the erythrocytes or red blood cells (which constitutes the second largest component of the blood at 45% total volume).
Once the blood components are separated during the blood fractionation, through the centrifugal force of the centrifuges, it becomes easier to identify the red blood cells infected by malaria-causing parasites: Plasmodium falciparum and P. vivax from the female Anopheles mosquitoes as they are lighter.

The World Health Organisation (WHO) in November 2017 released an estimated mortality rate of 445,000 out of about 216 million world malaria cases. Out of these huge number of cases, the developing continent of Africa, the sub-Saharan region, account for 91% and 90% of malaria deaths and cases respectively.

But in the developing nations of the world
there is the problem in both accessing quality healthcare and affording the cost of laboratory centrifuges. The centrifuges are not cheap, a descent centrifuge costs more a thousand dollars. Even if the health workers somehow acquire it, there is the problem of lack of electricity to power the machine.

Where Physics Meets Biology in Frugal Science

M. Saad Bhamla, an Assistant Professor of Bioengineering, Stanford University, Stanford, California and Manu Prakash, an
Associate Professor Of Bioengineering at Stanford University decided to leverage on the already existing toy- the whirligig.

The whirligig is a 5,000-year old toy which is simply made with a thread and a round object (button in the picture) with holes to pass the thread. By flipping the thread either in clockwise or anti-clockwise direction while holding the two ends of the thread, if you pull it an angular motion is induced in the button which allows it to spin very fast.

With this principle, the Paperfuge was inspired and created by the duo. The simple device was able to achieve speeds in excess of 125,000 rpm. You can watch this gif to see it in operation. Now the cost of this simple device is less than $1 at 20 cents.

The Paperfuge produces up to 30,000 g of centripetal forces and cable of separating the plasma from the red blood cells in less than 1.5 minutes while weighing only 2g and most especially costs only a fifth of a dollar at 20 cents! There is no need for electricity to get this "toy" working. Some conventional centrifuges that cost more than one thousand times the value of this, averages between 4000rpm to 10,000 rpm.

But Prakash is not yet done, he and his team developed a less than a dollar microscope that can compete with the paperfuge in operation and low cost. The cheap microscope is already for sale at the cost of 20 pcs at $35, i.e at $1.75 each at Foldscope webiste.

Just like the last creation, it does not require electricity as it can be powered by a button cell battery, a tiny lens, and a paper assembled in a similar manner as we fold an origami. The microscope is capable of magnifying up to 140 times at a resolution of 2 microns!

So, armed with less than a $3 equipment, a doctor/health worker can transverse the rural villages and other areas without electricity while carrying out the test with the same result as a standard laboratory with the equipment that is bulkier, costlier, and requires electricity to run.

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References

• ^Centrifuge
• ^{Children's Whirligig Toy Inspires a Low-Cost Laboratory Test}
• ^Whirligig
• ^{Hand-powered ultralow-cost paper centrifuge}
• ^{Measure the Rotational Speed of a Toy}
• ^{This 20-cent whirligig toy can replace a $1,000 medical centrifuge}
• ^{Paper Microscope}

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