Sensitivity improved with Parylene-C passivized on Lamb wave sensor for aPTT measurement through monitoring whole blood reaction

Abstract Blood clotting time monitoring is of great importance in predicting the risk of haemorrhage and cardiovascular diseases. In this study, a new P-Lamb wave sensor was developed to measure activated partial thromboplastic time (aPTT) with enhanced sensitivity. The sensor utilizes a piezoelectric and hydrophobic material, Parylene-C, as a waveguide for the P-Lamb wave sensor in order to monitor the aPTT in whole blood samples. With a smooth surface, the P-Lamb wave sensor reduced energy loss and prevented leaky modes, with a decrease of 33% ± 1.25% in the surface roughness and an increase of 2.75% ± 0.15% in the signal. The experimental results demonstrated that, compared to a quartz crystal microbalance (QCM), a P-Lamb sensor with high sensitivity (the frequency shift of a P-Lamb sensor is approximately 200 times greater than that of a QCM) improved stability and enhanced repeatability. Parylene-C worked as a phonon coupling layer, which improved the stability and sensitivity of the Lamb sensor. The relative standards deviation (RSD) of the aPTT measurement was 2.11%, which was 1.22 times lower than reported values. The P-Lamb wave sensor was also tested for its sensitivity to different concentrations of heparin and was found to exhibit an increase in coagulation time with an increasing heparin concentration. Compared to the SYSMEX CS 5100 haematology analyser, the clinical coefficient index (R 2 ) was 0.99467. Considering its compact size, low cost, and mass production of the chip unit, the developed P-Lamb wave sensor is a promising device for point-of-care diagnosis of haemostasis and personal health monitoring.