An integrated microfluidic system for dual aptamer assay utilizing magnetic-composite-membranes

Enzyme-linked immunosorbent assay (ELISA) is a popular detection method which employs two antibodies. In this study, we presented a new method which used electromagnetically-driven microdevices to form an integrated microfluidic chip for automating ELISA-like dual aptamer assay. First, an electromagnetic micropump was designed and fabricated by using composite membranes. It was formed by mixing iron particles with polydimethylsiloxane (PDMS) which could be deflected when a magnetic field was applied. The characterization of membrane deflections with different applied magnetic fields was measured. The electromagnets were made with cores surrounding 800 turns of brass coils which could produce a strong magnetic field to actuate the microdevice. The flow rate was measured to be 73.6 μl/min with an applied voltage of 8.0 V. Furthermore, we presented a design of an integrated microfluidic chip for automating dual aptamer assay. The chip integrated magnetically-driven micro-devices such as micropumps, microvalves and micromixers to automate the assay. It is promising for point-of-care applications.

I. Introduction

In the past decades, micro-electro-mechanical-system (MEMS) technology has provided advantages over traditional macroscale counterparts. Especially, micropumps have been investigated extensively and various concepts of actuation were developed [1]. For instance, pneumatic micropumps fabricated by soft lithography techniques were demonstrated for liquid delivery [2]. Alternatively, electroosmotic micropumps delivering drugs by using elctrokinetic forces were presented [3]. Similarly, piezoelectric micropumps showed decent performance in drug delivery in microchannels [4]. A magnetic peristaltic micropump was demonstrated by rotating motor shafts with magnets positioned. It then actuated the permanent magnets loaded inside the chamber layer generating peristaltic motion [5]. Magnetic actuation showed its potential for biomedical applications with the characteristics of large output forces in small scale.