NOVELTY - The microsystem (2) has two articulated arms (12, 14) between which compressed fluid i.e. inflammable mixture of fuel and oxidizer, is flown from a compressed fluid inlet nozzle (6) to an expanded fluid outlet nozzle (8) by displacing the arms with respect to one another. The arms are articulated such that the arms define a fluid pocket that is far away from the inlet nozzle for connecting the outlet nozzle, while increasing a volume. Electromechanical transducers (22, 24) convert mechanical energy produced by displacement of the arms into electrical energy.    USE - Microsystem i.e. micro-electromechanical system, for use in a pressure difference sensor of a wheel to convert pressure difference between expanded fluid and compressed fluid i.e. inflammable mixture of fuel and oxidizer, discharged from a combustion chamber of a combustion microengine of a fuel cell (all claimed), into mechanical displacement of arms.    ADVANTAGE - The microsystem converts the pressure difference between the expanded fluid and the compressed fluid into mechanical displacement of the arms without requiring an anti-return valve. The configuration of the microsystem permits the limitation of the flow rate of fluid through the microsystem so as to limit the pressure drop caused by the utilization of the microsystem, and permits efficient and simple cooling of the electronic chip. The microsystem has high energy efficiency even for less flow rate of the fluid.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a pressure difference sensor for measuring difference of pressure between compressed fluid and expanded fluid, comprising a microsystem for conversion of pressure difference between expanded fluid and compressed fluid into mechanical displacement of arms    (2) a wheel comprising a pressure difference sensor    (3) an electronic chip comprising a fluid compression microsystem    (4) a fuel cell comprising a combustion microengine    (5) a method for fabricating a microsystem for conversion of pressure difference between expanded fluid and compressed fluid into mechanical displacement of arms.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a microsystem for conversion of pressure difference in fluid into mechanical displacement of arms.    Microsystem for conversion of fluid pressure difference into mechanical displacement of arms (2)    Compressed fluid inlet nozzle (6)    Expanded fluid outlet nozzle (8)    Articulated arms (12, 14)    Electromechanical transducers (22, 24)