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Faster, more sensitive and easy to operate biosensing devices still are a need at important areas such as biomedical
diagnostics, food control and environmental monitoring. Recently, spintronic-devices have emerged as a promising
alternative to the existent technologies [1-3]. A number of advantages, namely high sensitivity, easy integration,
miniaturization, scalability, robustness and low cost make these devices potentially capable of responding to the existent
technological need.
In parallel, the field of microfluidics has shown great advances [4]. Microfluidic systems allow the analysis of small
sample volumes (from micro- down to pico-liters), often by automate sample processing with the ability to integrate
several steps into a single device (analyte amplification, concentration, separation and/or labeling), all in a reduced assay
time (minutes to hours) and affordable cost.
The merging of these two technologies, magnetoresistive biochips and microfluidics, will enable the development of
highly competitive devices.
This work reports the integration of a magnetoresistive biochip with a microfluidic system inside a portable and
autonomous electronic platform aiming for a fully integrated device. A microfluidic structure fabricated in
polydimethylsiloxane with dimensions of W: 0.5mm, H: 0.1mm, L: 10mm, associated to a mechanical system to align
and seal the channel by pressure is presented (Fig. 1) [5]. The goal is to perform sample loading and transportation over
the chip and simultaneously control the stringency and uniformity of the wash-out process.
The biochip output is acquired by an electronic microsystem incorporating the circuitry to control, address and read-out
the 30 spin-valve sensors sequentially (Fig. 1) [2]. This platform is being applied to the detection of water-borne
microbial pathogens (e.g. Salmonella and Escherichia coli) and genetic diseases diagnosis (e.g. cystic fibrosis) through
DNA hybridization assays.
Open chamber measurements were performed as described elsewhere [2]. Briefly, a 20 μl sample droplet is manually
dispensed over the chip, limited by a polymeric frame. When using the microfluidic system for sample loading, a known
volume of sample is introduced into the fluidic system through the help of a syringe pump at a controlled velocity.
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