Microfluidic device separates non-spherical bioparticles for rapid
23 April 2013
A team at the National University of Singapore (NUS) has
developed a novel microfluidic device that separates and detects
non-spherical bioparticles such as pathogenic bacteria and
malaria-infected red blood cells. It can potentially be used for
rapid medical diagnostics and treatment.
Though the team is focusing mainly on the rapid separation and
detection of bacteria from pathological samples at the moment, their
device has potential as a rapid diagnostic tool as well and could potentially replace an age-old method of detection
based on bacterial culture.
Bioparticles such as bacteria and red blood cells (RBC) are
non-spherical. Many are also deformable, for example, blood cells
may change shape when affected by different pathogens in the body.
Hence, the team’s shape-sensitive technique is a significant
discovery. Currently, separation techniques are mostly designed for
The microfluidic chip is only slightly
bigger than a Singapore $1 coin.
Source: National University of
Project leader Assoc Prof Zhang Yong said, “The old method was
developed about 100 years ago, but it is still being used today as
the mainstream technique because no new technique is available for
effective separation of bacteria from pathological samples like
blood. Many of the pathogenic bacteria are non-spherical but most of
microfluidic devices today are for separating spherical cells. Our
method uses a special I-shape pillar array which is capable of
separating non-spherical or irregularly-shaped bioparticles.”
The method developed by the NUS team can complete the diagnosis
process in less than an hour compared to 24-48 hours required for
bacterial detection by using conventional methods. Their device is
also efficient in separating red blood cells (RBCs) from blood
samples as RBCs are non-spherical. This enables rapid detection of
diagnostic biomarkers which reside in blood sample.
One of the most challenging aspects for the team was designing
and fabricating a device that is capable of detecting even the
smallest dimension of bioparticles and still provide reasonably good
How it works and moving forward
Scientists have tried to address the problem of separating
non-spherical bioparticles by using techniques such as restricting
the flow of particles but these have not shown to be as effective.
However, the NUS Bioengineering team’s I-shape pillar array device
has proven to be successful.
The I-shape pillar array induces rotational movements of the
non-spherical particles which in turn increases the effective
hydrodynamic size of the bioparticles flowing in the device,
allowing for efficient separation. Their design is able to provide
100 percent separation of RBCs from blood samples, outperforming
conventional cylindrical pillar array designs.
How the I-shape pillar array works.
Non-spherical cells such as rod-shaped ones are rotated by I-shape
pillar to increase their effective hydrodynamic size, isolating them
from samples. Source: National University of Singapore
The device can also potentially separate bioparticles with
diverse shapes and sizes. The team has tested their device
successfully on rod-shaped bacteria such as Escherichia coli
bacteria which can cause food poisoning). So far, this has been
difficult to achieve using conventional microfluidic chips.
Said Assoc Prof Zhang, “With our current findings, we hope to
move on to separate other non-spherical bioparticles like fungi,
with higher throughput and efficiency, circumventing the spherical
size dependency of current techniques.”
The team’s findings were published in Nature
Communications on 27 March 2013, titled: Rotational
separation of non-spherical bioparticles using I-shaped pillar
arrays in a microfluidic device.