Regulation of dynamic platelet aggregation in response to shear rate micro-gradients in a microfluidics device applying switching control

Arterial thrombosis continues to be a major cause of death in spite of intensive cardiovascular research. Recent discoveries have highlighted the primary role of shear rate microgradients in the aggregation of platelets and thrombus growth. This has prompted the development of in-vitro microfluidic platforms to study the underlying principles relating these variables. These platforms that typically operate in open-loop can be greatly refined through the incorporation of feedback control systems. This paper presents the design of an automatic controller for the regulation of platelet aggregation through modulation of shear rate in a state-of-the-art microfluidic platform. Such a controller is expected to deal with issues such as noise measurement noise, inter and intra-patient variability, and nonlinear behaviours. The controller is based on principles of variable structure systems, sliding mode control (SMC), coupled with a module of pulse-width modulation (PWM) in order to provide a near time-optimal time response with a smooth switching control action. Simulation results demonstrate the suitability of the controller for the regulation of platelet aggregation in the microfluidic platform of study, and eventually its application on automated diagnosis of shear rate-dependent platelet function.