Disposable biosensor for measuring red blood cell deformability using laser-diffraction technique

The laser-diffraction technique has been applied to design a microfluidic channel for measuring red blood cell deformability over a range of shear stress. A laser beam traverses a diluted blood suspension and is diffracted by RBCs in the volume. The diffraction patterns are captured by a CCD-video camera, linked to a frame grabber integrated with a computer. When deforming under decreasing shear stress in the microchannel, RBCs change gradually from the prolate ellipsoid towards a circular biconcave morphology. Both the laser-diffraction image and pressure were measured with respect to time, which enable to determine the elongation index (EI) and the shear stress. The range of shear stress is 0-20Pa and the measuring time is less than 2min. The elongation index (EI) is determined from an isointensity curve in the diffraction pattern using an ellipse-fitting program. The key advantage of this design is the incorporation of a disposable element that holds the blood sample, which enables the present system to be easily used in a clinical setting.