A miniature fiber optic force sensor measuring only 800 microns long and 100 microns in diameter was fabricated at the University of Maribor, Slovenia, to detect extremely slight forces exerted by small objects.
Unlike MEMS-based sensors, the new device does not require protective packaging and can be immersed in liquids as it is produced in an air-sealed cavity. A special etching process was used to design the sensor based 
The tiny fiber optic force sensor can measure extremely slight forces exerted by small objects and can be immersed in liquids. Source: Denis Donlagic, University of Mariboron a Fabry-Perot interferometer, an optical cavity formed by two parallel reflecting surfaces. The silica glass device consists of a thin silica diaphragm created at the tip of the fiber. The central part of the diaphragm is extended into a silica pole, which supports a round-shaped probe or a sensing cylinder apt for gauging measured force at subnanometer resolution.
The sensor was used to measure the Young modulus of a human hair and common dandelion and to track surface tension of a liquid by measuring the retraction force when a miniature cylinder was removed from a liquid. The researchers documented a force sensing resolution of about 0.6 µN with a sensor measurement range of about 0.6 mN.
The size of the force-sensing tip can be reduced to about 10 microns in diameter to design devices for the measurement of magnetic and electric fields or the surface tension of a liquid.
