Figure 1. The biomimetic haemostasis monitoring microdevice.

(a) Diagram of the device with line drawings below showing the design of the accelerating (pre-stenosed), uniform width (stenosed) and decelerating (post-stenosed) regions of the microchannels. The central stenosed region contains 12 parallel lanes of 200-μm-wide and 75-μm-high channels that repeatedly turn 60° a few times in each channel (scale bar, 500 μm). (b) Schematic of the haemostasis monitor device and method. Human whole blood is pushed or pulled by a syringe through an inline pressure sensor that connects to the device via tubing, and used to determine micro-clotting time. Optionally, fluorescence microscopy of fibrinogen and platelets allows simultaneous monitoring of thrombus formation. (c) Photograph of three haemostasis monitoring devices formed in a single piece of PDMS mould on top of a standard glass slide (75 × 50 mm). (d) Graph showing results of computational modelling of blood flow through the device. The wall shear rate across the length of the entire device (pre-stenosed through stenosed and post-stenosed; from left to right) is shown for various inlet flow velocities (u=0.01–0.5 m s⁻¹). (e) The computed wall shear gradients at the pre-stenosed (black circles) and post-stenosed (black squares) sections plotted against the mean wall shear at the stenosed section (line of linear regression (dotted line); goodness of fit, r²=0.99; average slope, 3.49 mm⁻¹). This linear relationship corresponds to a blood vessel that comprises of ∼55% stenosis. (f) Representative fluorescent micrographs of pre-stenosed, stenosed, and post-stenosed regions of the same microfluidic device, showing fibrin (top, green) and adhered platelets (bottom, red) after perfusing blood through the device, containing heparin (0.25 IU ml⁻¹), for 20 min (scale bar, 500 μm). (g) Scanning electron micrographs of a blood clot formed inside the device near the post-stenosed region shown at progressively higher magnifications (left to right; scale bar, 500, 50, 10, 5 and 1 μm) demonstrating the presence of fibrin networks containing trapped blood cells (3 images at left), including activated platelets (2 right images).