Dollar bill in a dollar microscope

Dec 18, 2014 • 8:13 PM UTC

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140x Magnification

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Manu Prakash

I am a faculty at Stanford and run the Prakash Lab at Department of Bioengineering at Stanford University. Foldscope community is at the heart of our Frugal Science movement - and I can not tell you how proud I am of this community and grassroots movement. Find our work here: http://prakashlab.stanford.edu

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Money is one thing that transfers amongst different people all the time. It carries a little piece of us every time it moves from one person to another.
Also, as an engineered object – it is something that all civilizations have invested time and effort to engineer. You want it to serve a very special purpose (an entire civilization might collapse if something goes wrong). So it’s a special object. Why am I spending time on this – everyone agrees, a dollar bill is important.
Finally – I wanted to use an object as a standard template for measuring magnification I can achieve. For this, it’s important to use an object that everyone carries around. What better object to choose from than a one dollar bill!!!!
Anyway; I was curious to see what a dollar bill looks like in a dollar microscope. So here we go, a one dollar bill inside a Foldscope.
Methods:
1. I folded a dollar bill so president washington’s face was facing the lens.
2. A dollar bill is thin enough that k can image it in reflected microscopy.
3. Since I know very specific features on a dollar bill; and know the size of them as well; I am also able to calculate what my absolute magnification is.
4. Researchers have quantified how money plays a role in transfer of infectious diseases; so I also wanted to compare a “dirty” bill from a newly “minted one”..
Observations: Here is a quick video of what a dollar bill looks like under Foldscope. You can easily see the fibers that a bill is made out of. At a small scale; the prints are very “random” and jagged. Next, I will look at many dollar bills to see if they are all the same at a microscopic level – or do they differ in patterns at the small scales.
I used my Foldscope with 140x lens and a light module (with condenser lens) and an iPhone 5 with magnetoc couplers for imaging.
Here is a video.