Microfluidic device and method of operation

A microfluidic device for determining at least one property of a fluid, the device comprising:

• a substrate having a surface and a first surface region defined thereon;
• a structure comprising a base supported by the substrate and a tube extending from the base and spaced apart from the surface of the substrate so as to be adapted for vibrating in a plane normal to the surface of the substrate, the tube having a continuous internal passage, a first portion adjacent the base and defining a fluid inlet of the passage, a second portion adjacent the base and defining a fluid outlet of the passage, and a distal portion relative to the base and spaced apart from the first surface region;
• a drive electrode within the first surface region of the substrate, adjacent the distal portion of the tube, and adapted for vibrating the tube to induce a drive motion and a twisting motion therein;
• first and second sensing electrodes on the substrate, adjacent the base and respectively the first and second portions of the tube, coupled to the first and second portions of the tube so as to sense deflections of the first and second portions of the tube when vibrated with the drive electrode, and adapted for producing outputs corresponding to the sensed deflections, each the first and second sensing electrodes extending less than half a distance from the base to the distal portion of the tube so as to be relatively less sensitive to the drive motion of the tube and relatively more sensitive to the twisting motion of the tube;
• a pair of electrodes adjacent the tube and on the surface of the substrate, a first of the pair of electrodes being between the drive electrode and the first sensing electrode and a second of the pair of electrodes being between the drive electrode and the second sensing electrode;
• and
• means for determining at least one property of the fluid from the outputs of the first and second sensing electrodes.