Biomedical Engineering Reference
In-Depth Information
Fig. 13 Telemedicine using smartphones. Reproduced from [
107
] with permission of The Royal
Society of Chemistry, and reprinted from with permission from [
127
] copyright (2011) American
Chemical Society
deviation means that the cell count can be corrected to give a clinically acceptable
count error. This integrated platform offers a low-cost solution that can provide
CD4 counts for monitoring HIV within 10 min. without the need for a skilled
labourer. The same lens-free platform could also be used for high-throughput
whole blood analysis in resource-poor settings. Seo et al. demonstrated automatic
counting of red blood cells of densities up to * 0.4 9 10
6
cells/lL from whole
blood samples [
91
]. The spatial resolution of this lensless technology is sufficient
to enable measurements of the volume of individual red blood cells as well as
being able to differentiate between three types of white blood cells: granulocytes,
monocytes and lymphocytes.
The fluid flow generated within microfluidic channels can be exploited to image
cells and organisms with sub-micron resolution without the need for bulky external
optical setups [
18
,
126
]. The technology, known as optofluidic microscopy,
involves passing the object over a CMOS sensor array using the laminar flow
within the microchannel. The chamber is illuminated from above using an LED
light source and the object casts shadows as it passes over the array. The series of
image slices acquired over time can be used to calculate an image of the original
object with a resolution comparable to conventional microscopy [
18
]. Yang and
co-workers first demonstrated this method by imaging Caenorhabditis elegans
with a resolution of 0.9 lm using a gravity-driven flow system. They also showed
that by controlling the flow electrokinetically, it was possible to image cells with a
similar resolution. More recently, the method was optimised by implementing a
pixel super-resolution algorithm to reconstruct images with a *0.75 lm resolu-
tion [
126
]. High-resolution imaging using a low-cost disposable device could find
its application in imaging blood cells or parasite morphologies for healthcare
diagnostics in the developing world.
The small size of microfluidic systems has allowed researchers to combine
them with mobile phones to drive telemedicine applications [
105
] (Fig.
13
). It is
predicted that by 2015 more than 86% of the world's population will own a mobile
phone, many of which are in the developing world [
4
]. It is easy to see that using
