The technique uses a combination of light and electric fields to position droplets and tiny particles, such as bacteria, viruses and DNA, which are contained inside the drops.
Other methods using either light or electric fields separately are able to position droplets or the particles they contain, but the new "hybrid optoelectric" device is able to do both, making it potentially practical for sensors and industrial processes, said mechanical engineering doctoral student Aloke Kumar.
Ordinarily, the particles inside droplets are detected when they randomly fall on a sensor's surface. However, the new method could improve sensor efficiency by actively moving particles to specific regions on an electronic chip for detection or analysis.
Such sensors might be used to quickly analyze blood, urine and other bodily fluids for a range of applications, including drug screening; paternity testing; detecting coronary artery disease, tumors and various inherited diseases including cystic fibrosis; and detecting infectious diseases and bacteria, viruses and fungi that are difficult to culture using conventional laboratory methods.
"This technique also would be good for DNA tests, such as those used on the TV program 'CSI,' to identify crime suspects using only a small blood sample," Wereley said. "The idea is to use a chip to quickly carry out laboratory procedures called polymerase chain reaction and capillary electrophoresis. The new technology also should be good for testing food and water for pathogens such as E. coli or salmonella."
Critical to the technology are electrodes made of indium tin oxide, a transparent and electrically conductive material commonly used in consumer electronics for touch-screen displays. Liquid drops are positioned on the electrodes, and the infrared laser heats up both the electrodes and the droplets. Then electric fields in the electrodes cause the heated liquid to produce a "microfluidic vortex" of circulating liquid. This vortex enables researchers to position the particles in the circulating liquid by moving the infrared laser. The particles accumulate only where the laser is shined.
"Sensors are one of the immediate applications of this technology," said Kumar, who may continue the work as a postdoctoral researcher at the Oak Ridge National Laboratories, where he will complete a two-year Eugene Wigner Fellowship starting this month. "We should be able to improve the efficiency of sensors at least 10 times."
Findings were detailed in a research paper appearing June 1 in the journal Langmuir. The paper was written by Kumar, Wereley and former Purdue doctoral student Han-Sheng Chuang, now a postdoctoral researcher at the University of Pennsylvania. The research is based at the Birck Nanotechnology Center at Purdue's Discovery Park.
Purdue has filed a U.S. patent application on the design.
The technique might be used to manufacture sensors and other devices by modifying a phenomenon called the coffee-ring effect, which causes residue to form when liquid evaporates. Because the particles in the residue form only where the infrared laser shines, the procedure might be used to precisely position particles to create structures and circuits for biosensors and electronics.
"We have successfully used this technique to create spatially controlled microassemblies, and we hope that this would interest other research groups looking into the coffee-ring effect," Kumar said.
The work has been supported with funding from the National Science Foundation and the Micro/Nano Fluidics Fundamentals Focus (MF3) Center at the University of California, Irvine.
Emil Venere | EurekAlert!
Ultrathin device harvests electricity from human motion
24.07.2017 | Vanderbilt University
Stanford researchers develop a new type of soft, growing robot
21.07.2017 | Stanford University
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
21.07.2017 | Event News
19.07.2017 | Event News
12.07.2017 | Event News
25.07.2017 | Physics and Astronomy
25.07.2017 | Earth Sciences
25.07.2017 | Life Sciences