Purdue researchers have created a new type of microtweezers capable of manipulating objects to build tiny structures, print coatings to make advanced sensors, and grab and position live stem cell spheres for research. Image: Birck Nanotechnology Center
Researchers have created new microtweezers capable of manipulating objects
to build tiny structures, print coatings to make advanced sensors, and grab and
position live stem cell spheres for research.
The microtweezers might be used to assemble structures in
microelectromechanical systems, or MEMS, which contain tiny moving parts. MEMS
accelerometers and gyroscopes currently are being used in commercial products.
A wider variety of MEMS devices, however, could be produced through a
manufacturing technology that assembles components like microscopic Lego pieces
moved individually into place with microtweezers, said Cagri Savran, an
associate professor of mechanical engineering at Purdue University.
“We’ve shown how this might be accomplished easily, using new compact
and user-friendly microtweezers to assemble polystyrene spheres into 3D
shapes,” he said.
Research findings were detailed in a paper that appeared online in the Journal of Microelectromechanical Systems,
or JMEMS. The paper was written by
Savran, mechanical engineering graduate students Bin-Da Chan and Farrukh
Mateen, electrical and computer engineering graduate student Chun-Li Chang, and
biomedical engineering doctoral student Kutay Icoz.
The new tool contains three main parts: A thimble knob from a standard
micrometer, a two-pronged tweezer made from silicon, and a “graphite
interface,” which converts the turning motion of the thimble knob into a
pulling-and-pushing action to open and close the tweezer prongs. No electrical
power sources are needed, increasing the potential for practical applications.
Other types of microtweezers have been developed and are being used in
research. However, the new design is simpler both to manufacture and operate,
The design contains a one-piece compliant structure, which is springy like a
bobby pin or a paperclip. Most other microtweezers require features such as
hinges or components that move through heat, magnetism or electricity, complex
designs that are expensive to manufacture and relatively difficult to operate
in various media, he said.
The tweezers make it feasible to precisely isolate individual stem cell
spheres from culture media and to position them elsewhere. Currently, these
spheres are analyzed in large groups, but microtweezers could provide an easy
way to study them by individually selecting and placing them onto analytical
devices and sensors.
“We currently are working to weigh single micro particles, individually
selected among many others, which is important because precise measurements of
an object’s mass reveal key traits, making it possible to identify composition
and other characteristics,” Savran said. “This will now be as easy as
selecting and weighing a single melon out of many melons in a
That work is a collaboration with the research group of Timothy Ratliff, the
Robert Wallace Miller Director of Purdue’s Center for Cancer Research.
The microtweezers also could facilitate the precision printing of chemical
or protein dots onto microcantilevers, strips of silicon that resemble tiny
diving boards. The microcantilevers can be functionalized, or coated with
certain chemicals or proteins that attract specific molecules and materials.
Because they vibrate at different frequencies depending on what sticks to the
surface, they are used to detect chemicals in the air and water.
Generally, microcantilevers are functionalized to detect one type of
substance by exposing them to fluids, Savran said. However, being able to
microprint a sequence of precisely placed dots of different chemicals on each
cantilever could make it possible to functionalize a device to detect several
substances at once. Such a sensing technology also would require a smaller
sample size than conventional diagnostic technologies, making it especially
The new microtweezers are designed to be attached easily to translation
stages currently used in research. These stages are essentially platforms on
which to mount specimens for viewing and manipulating. Unlike most other
microtweezers, the new device is highly compact and portable and can be easily
detached from a platform and brought to another laboratory while still holding
a micro-size object for study, Savran said.
The two-pronged tweezer is micromachined in a laboratory called a
“clean room” with the same techniques used to create microcircuits
and computer chips. The research was based at the Birck
in Purdue’s Discovery
Purdue has filed for a provisional patent on the design.