Picotechnology
Nano technology deals with objects in the nano metre size range (10-9 metres). Pico technology is one thousand times smaller (10-12 metres). In this world objects are measured in terms of picometres (pm). For example a Gold atom in a crystal lattice will measure approximately 270pm in diameter. Thermal vibration at room temperature will produce movement in the order of 20pm. On this scale an atoms nuclear diameter is in the region of 0.002pm and the wavelength of red light is 650,000pm.
Various techniques have been developed over the years to make measurements at picometre distances, such as capacitance transducers and laser based devices.
So when an inventor approached X-AT with a device he claimed that could measure displacements to 50pm accuracy that he had built in his living room it was greeted with initial scepticism. He had previously approached many universities and companies with this device but no one believed his claim. X-AT decided to examine his prototype and a series of simple tests were performed. These indicated that the physical basis on which the device operated was probably valid, but not fully understood. The experiments were able to show that the device was able to measure very small displacements, giving repeatable results, within the experimental accuracy of the testing apparatus. Improvements were subsequently made to the design by rebuilding a second design of the mechanical prototype and improved electronic circuitry. These were used in a second series of tests, to gain greater understanding of the devices operation and characteristics.
It soon became apparent that in order to make a very accurate assessment of the device it would require advanced testing methods and apparatus, which were not available at Exeter. The original mechanical prototype and new electronics was taken to the National Physical Laboratory (NPL) in London. A series of tests were performed with distance movements measured by the device being compared against measurements made by a very accurate laser interferometer. These experiments showed that the device could measure displacements with a sensitivity of 40pm.
THE TECHNOLOGY
The device functions by setting up and detecting an electronic conduction between two conductors in extreme proximity to one another. Not actually in "classical" physical contact, the conductors have a sub angstrom (10-10 metres) separation distance between them. Such conduction has been termed Field Electronic Emission (FEE). The magnitude of this current flowing between the conductors is strongly dependent on the minute separation between them and is used to indicate displacement.
The device provides a method of precisely moving one of the conductors to "track" and measure a displacement together with controlling the separation distance between the conductors. The important key to this invention is the method by which this "tracking" is achieved. It is performed via a series of pulsed, discrete, monotonic movement steps, each step being in the sub-angstrom range. Unlike most displacement measuring devices the movement of the conductor is not substantially limited in its movement range. Therefore, the device does not suffer from the usual inverse relationship between measurement sensitivity and measurement range; whereby an increase in measurement range is at the expense of a decrease in measurement sensitivity and vice versa.
The development and marketing of the device has now been taken up by A-Metrics LLC, a North Carolina based company.
For further information about this device contact:-
P.R.Armitage, X-AT, SECaM, University of Exeter or
A-Metrics LLC, 7804 Fairview Road, Suite 317, Charlotte, North Carolina 28226 USA
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