Applied physics - Weight inside

Nanoscale mechanical resonators can be used to measure the mass of particles with extraordinarily high resolution down to the zeptogram scale — that's multiples of 10−21 grams. Such astonishing resolution has not been possible in many practical applications such as medical diagnostics or environmental monitoring, where the presence of fluids dampens the mechanical vibrations that make the system work. Now a team from MIT and the Santa Barbara labs of Innovative Micro Technology and Affinity Biosensors has devised an ingenious way around this problem by placing the fluid inside the resonator. Their vacuum-packaged resonator, with the solution with particles of interest held in microfluidic channels, can weigh single nanoparticles and bacteria at subfemtogram (10−15 g) resolution.