Itsy Bitsy Hole Measurer

Gauging the width of a hole less than a hundredth of an inch is not something you do with a tape measurer.  A new technique records the shadows of a glass probe to determine hole dimensions to an accuracy of 35 nanometers, or roughly a millionth of an inch.

"Our probe has a much smaller measurement uncertainty than other available methods and it is very cost effective to make," said Bala Muralikrishnan from the University of North Carolina.

The $100 probe is a flexible glass fiber - three quarters of an inch long and two thousandths of an inch wide.  The beaded tip is inserted into a hole and moved very carefully around.  The upper part of the fiber will bend as the tip comes up against the edges of the hole. 

To record the amount of bending, light is shone down the length of the fiber.  The more the fiber bends, the longer its shadow will be on the surface.  A camera detects the position of the shadow, from which the size of the hole is determined.

The smallest hole that can be measured is 100 microns wide - twice the width of the fiber.

This method could be applied to fuel nozzles, biomedical stents, ink jet cartridges and other precision-engineered products.  In the image above, the glass probe is being inserted into an optical "ferrule," a device for connecting optical fibers used in communications systems.  

• High-tech Probes Sneak Inside Your Cells
• The World's Smallest Motor
• Image Gallery: Micromachines

-- LiveScience Staff

Credit: National Institute of Standards and Technology