MICROWAVE ENABLED PORTABLE, LABEL-FREE, HIGH-THROUGHPUT DETECTION AND CONTENT SENSING SYSTEM FOR LAB ON A CHIP PLATFORMS

摘要

This study reports a microwave-microfluidics integrated approach capable ofperforming dropletdetection at high-throughput as well as content sensing of individual dropletswithout chemical orphysical intrusion. The sensing system consists of a custom microwavecircuitry and a spiral-shapedmicrowave resonator that is integrated with microfluidic chips where dropletsare generated. Themicrowave circuitry is very cost effective by using off-the-shelf componentsonly. It eliminates theneed for bulky benchtop equipment, and provides a compact, rapid and sensitivetool compatible forLab-on-a-Chip (LOC) platforms. To evaluate the resonator's sensing capability,it was first appliedto differentiate between single-phase fluids which are aqueous solutions withdifferentconcentrations of glucose and potassium chloride respectively by measuring itsreflection coefficientas a function of frequency. The minimum concentration assessed was 0.001 g ml-1 for potassiumchloride and 0.01 g ml-1 for glucose. In the droplet detection experiments, itis demonstrated thatthe microwave sensor is able to detect droplets generated at as highthroughput as 3.33 kHz. Aroundtwo million droplets were counted over a period of ten minutes without anymissing. For dropletsensing experiments, pairs of droplets that were encapsulated with biologicalmaterials weregenerated alternatively in a double T-junction configuration and clearlyidentified by the microwavesensor. The sensed biological materials include fetal bovine serum, penicillinantibiotic mixture,milk (2% mf) and D-(+)-glucose. This system has significant advantages overoptical detectionmethods in terms of its cost, size and compatibility with LOC settings andalso presents significantimprovements over other electrical-based detection techniques in terms of itssensitivity andthroughput.