Piezoelectric layer embedded-microdiaphragm sensors for the determination of blood viscosity and density

We introduce a lead zirconate titanate [PZT; Pb(Zr0.52Ti0.48)O-3] microdiaphragm resonating sensor packaged in a polydimethylsiloxane chip. The proposed sensor can measure the density and viscosity of a liquid that is within the density and viscosity regime of blood (1.060 x 10(3) kg/m(3), 3-4 cP). To verify the basic characteristics of the sensor, viscous solutions were prepared from glycerol and deionized water with a density in the range from 0.998 to 1.263 x 10(3) kg/m(3) and a viscosity in the range from 1 to 1414 cP. We measured the frequency responses of the sensor before and after injecting the viscosity-and density-controlled liquid under the bottom of the microdiaphragm. The resonant frequencies in the (1,1) and (2,2) modes decreased linearly as a function of the liquid density in the range from 0.998 to 1.146 x 10(3) kg/m(3) with a sensitivity of 28.03 Hz/kg.m(-3) and 81.85 Hz/kg.m(-3), respectively. The full width at half maximum had a logarithmic relationship with the liquid viscosity in the viscosity range from 1 to 8.4 cP. The quality factor (Q-factor) for the 50% glycerol/water mixture was determined to be greater than 20 for both the (1,1) and the (2,2) modes, indicating that the microdiaphragm resonating sensor is suitable for measuring the density and viscosity of a liquid within a density range from 0.998 to 1.1466 x 10 3 kg/m(3) and a viscosity range from 1 to 8.4 cP. These density and viscosity ranges span the regime of possible changes of blood characteristics. The microdiaphragm resonating sensors were also tested with a real human serum to verify that the sensor is suitable for measuring the viscosity and density of blood. Therefore, the PZT microdiaphragm resonating sensor could be utilized for early diagnosis of diseases associated with changes in the physical properties of blood. (C) 2014 AIP Publishing LLC.