A TINY microscope the size of a grain of sand could soon be looking at you from the inside. Its developers say it can zoom in on individual cells inside the body to look for early signs of disease and could eventually be implanted for long-term health monitoring.
Unlike today鈥檚 endoscopic cameras, the 鈥渕icro-microscope鈥� can magnify individual cells and inspect the structures within them. 鈥淲e can focus on different layers throughout the structure and then analyse them,鈥� says Luke Lee, whose team built the device at the University of California at Berkeley.
The microscope is based on a desktop version called a confocal microscope, which collects light from only a small spot on a specimen at a time to give greater resolution. A confocal microscope fires a laser beam through a series of mirrors and a lens. By moving the mirrors and adjusting the focus of the lens, the beam can be scanned across tissue and even probe beneath the surface to build up a 3D image.
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Injecting fluorescent dyes into the tissue allows the microsope to look for specific molecules such as proteins. Reflected or fluorescent light from the tissue bounces back through the microscope where it is detected by a light sensor. The desktop microscopes are the size of a PC. They can look at biopsies-tissues that have been cut out of the body-but are far too cumbersome for examining actual living tissue internally.
Lee says his miniaturised version fits into just one cubic millimetre. Instead of using mirrors, he has built his microscope with three plastic lenses, each less than a tenth of a millimetre thick.
Each lens was made by squeezing a tiny drop of polymer into a silicon ring and solidifying it with ultraviolet light. Each ring was then fixed onto a silicon bracket, in between two silicon 鈥減istons鈥� that use electrostatic charges to move each lens back and forth (see Diagram).
To direct light as it moves through the microscope, the lenses are stacked on top of each other. The top two lenses can move horizontally at right angles to each other. The third lens is fitted to a silicon platform driven by a piston that can move it up and down, and so change the focal point of light passing through it.
To complete the microscope, a tiny blue light-emitting diode (LED) is fixed above the lens stack. Light from the LED can be shifted left and right, or 鈥渋n and out鈥� as it passes through the first two lenses before being focused by the third lens. Light reflected from the specimen bounces back up through the lenses and is reflected onto a photosensor.
Lee says the microscope will first be clipped onto the tip of a catheter which will carry power to it and allow images to be sent back to a computer. The device could be especially useful for checking the success of experimental therapies. If, for example, insulin-producing cells were implanted into the pancreas of someone with diabetes, the microscope could zoom in to confirm whether the cells are producing insulin.
Eventually, Lee hopes to build a power source into the microscope as well as a radio-frequency transmitter to beam images from within the body. The whole system could then be implanted to constantly monitor tissues.