INTEL's latest microchip technology has created transistors 22 nanometres wide, a mere 200 times the width of a hydrogen molecule. Carving the tiny features is difficult and expensive, but in another realm of microchips altogether, something odd is happening: chips are being made on an outsized scale and then shrunk to the required size, avoiding much fiddly hassle.
The shrinking innovation is happening in the field of the "lab-on-a-chip". Such chips are typically plastic slivers scored with serried ranks of fluid-filled microchannels and recessed pools for chemical reactions to occur in; they are often replete with deposits of chemicals, cells and proteins of interest.
The idea? To provide a swift diagnostic tool: add some body fluids and let the gadget look for telltale chemical changes that reveal biomarkers linked to various diseases. One day, a handheld gadget may scan you for a multitude of ailments.
But there's a problem, says biochemical engineer Christophe Marquette and colleagues at the Claude Bernard University in Lyon, France. Microfluidic chips are hard to manufacture and are consequently too expensive for throwaway systems. What's more, the difficulty of making them so tiny constrains the creativity of their designers.
The Lyon team's answer is simple but powerful: carve and print the features on a large chip made of PolyShrink, a heat-shrinkable polymer, which is then warmed.
So far they have shrunk a 230-micrometre-square biochip down to 100-micrometres square. Of course, the material does not disappear as it shrinks - instead it gets thicker, moving from 15 to 85 micrometres thick.
Crucially, its features remained in good shape. In tests, the chip's reaction chambers, drug reservoirs, channels and patterns of cells shrunk uniformly, maintaining the same relative dimensions right down to the final chip size (Lab On A Chip, DOI: 10.1039/b913253h). Even complex spiral-shaped channels were faithfully reproduced.
Marquette says this "print 'n' shrink" technology could give designers of such chips more room to manoeuvre, as well as allowing for greater precision in their manufacture.
This was first published in October 2009