A sensor is provided for detecting and characterizing particles in a fluid. The sensor has a microfluidic channel for receiving the fluid sample, an acoustic transducer module configured to generate a standing wave for concentrating the particles in a region of the microfluidic channel; an optical detection module configured to detect optical signals scattered by the particles upon illuminating the region of the fluid sample with a light source; and a data processing module configured to characterize the particles of the fluid sample based on the optical signals using a classifier.