Researchers for the first time have discovered a high-tech scale which is minuscule, for weigh living bacteria and immune cells. This technique could help develop inexpensive, portable diagnostic devices for community health workers for example; a device could be created to count CD4 immune cells in AIDS patients, which would tell how far the disease has progressed. This new scale can measure living cells and nanoparticles down to a femtogram, or about the weight of an E. coli bacterium.

Previous methods of weighing involved molecule being placed on top of tiny silicon slab inside a vacuum. But living cells cannot survive in a vacuum and must be measured in a fluid, which would interfere with the measurement if it surrounded the slab. A group of MIT scientists solved this problem by pumping the fluid containing the sample of cells through a microchannel inside the slab.
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