Biomedical Engineering Reference
In-Depth Information
Fig. 7.10 Microfluidic chip
comprising eight parallel
microfluidic channels for
high-throughput sample
analysis
7.5
Miniaturization of Desktop Biostation
In order to facilitate effective deployment in the field by nontechnical users,
it is important that the wash-free assay be integrated into an ultraportable and
battery-powered detection module [ 16 ]. This capability should obviate the need
for a constant supply of electricity or a designated laboratory. Since the form
factor of GMR nanosensors is very small, dictated only by lithography used
in their fabrication, by miniaturizing the electronic components, it is possible
to replace a laboratory full of equipment with a handheld and battery-powered
device (Fig. 7.11 ). No lasers or expensive charge-coupled device (CCD) cameras
are required for the platform, which uniquely positions GMR-based biosensors for
ultraportable, POC applications.
The detection platform has been designed to have two components: a reusable
handheld detection module the size of a handheld calculator (Fig. 7.12 a) and a
disposable detection stick (Fig. 7.12 b). The handheld detection module consists of
two boards. First, the data acquisition board (DAQ) has both analog and digital
subcircuits. The analog circuits are comprised of the excitation signal generation,
the field signal generation, and the front end. The front end for the sensor is a
classical Wheatstone bridge with a high-gain instrument amplifier. Also contained
on the DAQ board is the microprocessor which does the digital signal processing
(DSP) and handles all of the user interactions. The other board in the detection
module is the coil board which contains a power amplifier and a planar electro-
magnet used to generate the magnetic field to modulate the sensors. The disposable
stick, which is the second component of the overall detection platform, contains no
electronics, just the GMR nanosensor array with 8 individually addressable sensors
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