In 2006, Michelle Khine arrived at the University of California's brand-new Merced campus eager to establish her first lab. She was experimenting with tiny liquid-filled channels in hopes of devising chip-based diagnostic tests, a discipline called microfluidics. The trouble was, the specialized equipment that she previously used to make microfluidic chips cost more than $100,000 -- money that wasn't immediately available.
Racking her brain for a quick-and-dirty way to make microfluidic devices, Khine remembered her favourite childhood toy: Shrinky Dinks, large sheets of thin plastic that can be colored with paint or ink and then shrunk in a hot oven. "I thought if I could print out the [designs] at a certain resolution and then make them shrink, I could make channels the right size for microfluidics" she says.
To test her idea, she whipped up a channel design in AutoCAD, printed it out on Shrinky Dink material using a laser printer, and stuck the result in a toaster oven. As the plastic shrank, the ink particles on its surface clumped together, forming tiny ridges. That was exactly the effect Khine wanted. When she poured a flexible polymer known as PDMS onto the surface of the cooled Shrinky Dink, the ink ridges created tiny channels in the surface of the polymer as it hardened. She pulled the PDMS away from the Shrinky Dink mould, and voilà: a finished microfluidic device that cost less than a fast-food meal.
Skepticism arose. How on earth, critics wondered, could you use a toy to make a sophisticated device that's normally forged from high-grade silicon? Admittedly Shrinky Dink microfluidics isn’t perfect -- minute ink splatters from the printer, for instance, can give rise to slight irregularities in the finished channels. Still, glitches like these don't pose a problem for most applications. What’s more: used in the traditional way, PDMS can absorb proteins, throwing off the results of sensitive tests. Kline has begun to make chips directly out of the Shrinky Dinks by etching the design into the plastic using syringe tips. As the plastic shrinks, the channels become narrower and deeper -- perfect for microfluidics. This allows even three-dimensional chips to be made by melting several etched Shrinky Dinks together. The whole process, from design to finished chip, takes only minutes.
Source: MIT Technology Review
Photo Credit: Dave Lauridsen
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