Research Category: Conveyor System
Researchers: Prof. Martin Z. Bazant|
Location: Massachusetts Institute of Technology, United States
Employing a novel three-dimensional alternating-current
electro-osmotic (3D ACEO) pump, a group of
MIT researchers led by Prof.
Martin Z. Bazant may have just taken a substantial leap forward in the
development of microfluidics, a leap that could enable portable, or even
implantable, biomedical lab-on-a-chip devices.
Existing ACEO pumps move fluids over a planar microelectrode array applying an
AC voltage. “However,” says Prof. Bazant, “this design is inefficient, since it
involves opposing surface flows, where one direction slightly ‘wins’ over the
other due unequal electrode widths.” Prof. Bazant theoretically predicted that
dramatic increases in flow rate could be achieved – by more than order of
magnitude – by using electrodes with raised steps. His 3D design actually turns
what was previously considered a drawback of ACEO into a means of increasing
flow speed. “The basic idea,” says Bazant, “is to recess the reverse flows to
form ‘rollers’ for the raised pumping flow, thus forming a ‘fluid conveyor
Bazant’s collaborators in the lab of Prof. Todd Thorsen have demonstrated that
the concept really works. Using the new 3D design, the team has fabricated, by
far, the fastest low voltage (<10 Volt) AC electrokinetic pumps. They expect to
achieve mm/second velocities after design optimization. To reach similar flow
speeds, standard DC electro-osmotic pumps require a high voltage power supply (>
100 Volt) and produce undesirable electrochemical reactions. By working at
battery voltages with low power consumption (< 10 milliWatt), the team foresees
the possibility of portable lab-on-a-chip devices, where fluids are pumped and
mixed at the micron scale by 3D ACEO and other phenomena of induced-charge
electro-osmosis (ICEO), also springing from Bazant’s theoretical work.
Research in ICEO flows is ongoing, with the goal of being able to manipulate
common electrolytes, such as blood and other biological fluids, through
microchannels. Current pressure-driven systems, many of which require
substantial external plumbing, are not very sensitive to the fluid, but they
offer little local flow control and require extraordinary – even unfeasible –
pressures when channel sizes approach the micron scale. ICEO can generate fast,
tunable flows in microchannels, but seems limited to relatively dilute
electrolytes (< 10 mM), for reasons currently under investigation. Nevertheless,
Jeremy Levitan (Bazant's postdoc) has successfully demonstrated rapid DNA
hydridization microarrays and ELISA immunoassays using ICEO flows in 10x diluted
buffer solutions. These are important milestones for Prof. Thorsen’s vision of a
portable ICEO-based microfluidic device for early detection of exposure to toxic
warfare agents. Similar devices could also be used for point-of-care diagnostics
in civilian medical applications.
A paper on Bazant’s theoretical work (with former postdoc, Yuxing Ben) is
published online and in press at the journal Lab on a Chip. A related paper on
the team’s experimental progress will appear in an upcoming edition of Applied
Physics Letters (coauthored by graduate student, J. P. Urbanski, postdoc, Jeremy
Levitan, and Profs. Thorsen and Bazant). A company, ICEO, Inc., has been created
to commercialize the technology.
The new pumping devices are being developed as part of a broader effort to
increase the safety of Soldiers and first responders at
MIT's Institute for Soldier
Note for Microfluidics
Microfluidics deals with the behavior, precise control and manipulation of
fluids that are geometrically constrained to a small, typically sub-millimeter,
scale. It is a multidisciplinary field intersecting engineering, physics,
chemistry, microtechnology and biotechnology, with practical applications to the
design of systems in which such small volumes of fluids will be used.
Microfluidics has emerged in the beginning of the 1980s and is used in the
development of inkjet printheads, DNA chips, lab-on-a-chip technology,
micro-propulsion, and micro-thermal technologies.
The behavior of fluids at the microscale can differ from 'macrofluidic' behavior
in that factors such as surface tension, energy dissipation, and fluidic
resistance start to dominate the system. Microfluidics studies how these
behaviors change, and how they can be worked around, or exploited for new uses.
At small scales (channel diameters of around 100 nanometers to several hundred
micrometers) some interesting and unintuitive properties appear. The Reynolds
number, which characterizes the presence of turbulent flow, is extremely low,
thus the flow will remain laminar. Thus, two fluids joining will not mix readily
via turbulence, so diffusion alone must cause the two fluids to mingle.
Microfluidic structures include on one hand micropneumatic systems, i.e.
microsystems for the handling of off-chip fluids (liquid pumps, gas valves,
etc), and on the other hands microfluidic structures for the on-chip handling of
nano- and picolitre volumes. The commercially most successful application today
is the inkjet printhead.
Advances in microfluidics technology are revolutionizing molecular biology
procedures for enzymatic analysis (e.g., glucose and lactate assays), DNA
analysis (e.g., polymerase chain reaction and high-throughput sequencing), and
proteomics. The basic idea of microfluidic biochips is to integrate assay
operations such as detection, as well as sample pre-treatment and sample
preparation on one chip.
An emerging application area for biochips is clinical pathology, especially the
immediate point-of-care diagnosis of diseases. In addition, microfluidics-based
devices, capable of continuous sampling and real-time testing of air/water
samples for biochemical toxins and other dangerous pathogens, can serve as an
always-on "bio-smoke alarm" for early warning.
Note for Electroosmotic Flow
Electroosmotic flow is the motion of ions in a solvent environment through very
narrow channels, where an applied potential across the channels cause the ion
migration. Electroosmotic flow is an essential component in chemical separation
techniques, notably capillary electrophoresis. Electroosmotic flow can occur in
natural unfiltered water, as well as buffered solutions.
The cause of electroosmotic flow is an electrical double layer that forms at the
stationary/solution interface. In capillary electrophoresis, the narrow channels
are made up of silica, and silanol groups form the inner surface of the
capillary column. These silanol groups are ionized above pH3. Thus, the inner
surface of the channel is negatively charged. In solutions containing ions, the
cations will migrate to the negatively charged wall. This forms the electric
double layer. When an electrical potential is applied to the column, with an
anode at one end of the column and a cathode at another, the cations will
migrate towards the cathode. Since these cations are solvated and clustered at
the walls of the channel, they drag the rest of the solution with them, even the
anions. This results in an electroosmotic flow, not to be confused with the
Electroosmotic flow was first reported in 1809 by F.F. Reuss in the Proceedings
of the Imperial Society of Naturalists of Moscow. He showed that water could be
made to flow through a plug of clay by applying an electric voltage. Clay is
composed of closely packed particles of sand and other minerals, and water flows
through the narrow spaces between particles just as it would through a narrow
glass tube. Any combination of an electrolyte (a fluid containing dissolved
ions) and insulating solid would generate electro-osmotic flow, though for
water/silica (that is what glass or sand is, chemically) the effect is
particularly large. Even so, flow speeds are typically only a few millimeters
An early application of electroosmotic flow was in drying or decontaminating
soil. There has been a great deal of interest and research in electroosmotic
flow in the last decade, since it was realized that it provides a very efficient
way to generate fluid flows in microfluidic devices, including electroosmotic
pumps that can generate flow rates as large as a few milliliters per minute, and
pressures as large as hundreds of atmospheres. Another reason for the increased
interest in electroosmotic flow is its effect on capillary electrophoresis,
where the flow tends to counteract the electric field used to drag the DNA
Note for Conveyor Belt
A belt conveyor consists of two or more pulleys, with a continuous loop of
material - the conveyor belt - that rotates about them. One or both of the
pulleys are powered, moving the belt and the material on the belt forward. The
powered pulley is called the drive pulley while the unpowered pulley is called
the idler. There are two main industrial classes of belt conveyors; Those in
general material handling such as those moving boxes along inside a factory and
bulk material handling such as those used to transport industrial and
agricultural materials, such as grain, coal, ores, etc. generally in outdoor
locations. Generally companies providing general material handling type belt
conveyors do not provide the conveyors for bulk material handling. In addition
there are a number of commercial applications of belt conveyors such as those in
The belt consists of one or more layers of material they can be made out of
rubber. Many belts in general material handling have two layers. An under layer
of material to provide linear strength and shape called a carcass and an over
layer called the cover. The carcass is often a cotton or plastic web or mesh.
The cover is often various rubber or plastic compounds specified by use of the
belt. Covers can be made from more exotic materials for unusual applications
such as silicone for heat or gum rubber when traction is essential.
Material flowing over the belt may be weighed in transit using a beltweigher.
Belts with regularly spaced partitions, known as elevator belts, are used for
transporting loose materials up steep inclines. Belt Conveyors are used in
self-unloading bulk freighters and in live bottom trucks. Conveyor technology is
also used in conveyor transport such as moving sidewalks or escalators, as well
as on many manufacturing assembly lines. Stores often have conveyor belts at the
check-out counter to move shopping items. Ski areas also use conveyor belts to
transport skiers up the hill. A wide variety of related conveying machines are
available, different as regards principle of operation, means and direction of
conveyance, including screw conveyors, vibrating conveyors, pneumatic conveyors,
the moving floor system, which uses reciprocating slats to move cargo, and
roller conveyor system, which uses a series of powered rollers to convey boxes
The longest belt [conveyor system] in the world is in Western Sahara. It is 100
km long, from the phosphate mines of Bu Craa to the coast south of El-Aaiun. The
longest single belt conveyor runs from Meghalaya in India to Sylhet in
Bangladesh. It is 17 miles long and conveys limestone and shale. The Conveyor
belt was manufactured in about 300 meter lengths and was joined together and
installed on the conveyor at site. The job was carried out by NILOS India Pvt.
Ltd. in Chennai India.The Idlers or Rollers for this very special Conveyor was
produced and supplied by Kali BMH Systems (P) Ltd, Kumbakonam, India. The Idler
Rollers were unique for the project that they were designed to accommodate both
Horizontal and Vertial Curves along the terrain.
Conveyors are used as components in automated distribution and warehousing. In
combination with computer controlled pallet handling equipment this allows for
more efficient retail, wholesale, and manufacturing distribution. It is
considered a labor saving system that allows large volumes to move rapidly
through a process, allowing companies to ship or receive higher volumes with
smaller storage space and with less labor expense.
In figure, A scanning electron microscope image shows the stepped microelectrodes in an experimental realization of Prof. Martin Bazant's 3D ACEO array. This new design greatly increases the flow rate per voltage compared to traditional planar ACEO arrays.