Nanotechnology for Detection of Small Mass Difference

Mostly, mass of a macroscopic object is determined by comparing the gravitational forces experienced by the object and the body of known mass. Relative uncertainty in 1kg is pretty small say one part in 10(9). However, gravitational force of an object of molecular scale is too feeble to detect. Hence, normal method of using a balance will not do for mass measurement on the microscopic scale. Measurement of mass at the microscopic scale is very vital as it serves powerful tool that can provide information about the molecular and atomic composition of an object, detection, prevention and treatment of various diseases. Mechanical balances with electronic devices can detect only up to 0.1μg. An alternate method to measure the mass of an object is to consider mass as quantification of inertia. This principle is used in mass spectroscopy. In this the trajectory of an ionised particle in a strong electromagnetic field provides a precise measure of the inertia of the particle and hence a measure of its mass. Mass spectroscopy is able to distinguish ionised particles that differ by a single atomic mass unit. One atomic mass unit is equal to 1.66 ×10(−27)kg. However, mass spectroscopy is restricted to ionised particles so it cannot be applied to all microscopic objects, which are neither in charged state nor can be charged. So for smaller masses, one has to depend upon certain other phenomenon.