This image, taken with a transmission electron microscope, shows 29.1-nm nanoparticles that were used to make conductive ink. Image credit: Yun Hwan Jo, et al. ©2011 IOP Publishing Ltd.
(PhysOrg.com) -- Almost all electronic devices contain printed circuit boards, which are patterned with an intricate copper design that guides electricity to make the devices functional. In a new study, researchers have taken steps toward fabricating circuit boards with an inkjet printer. They have synthesized tin (Sn) nanoparticles and then added them to the ink to increase its conductivity, leading to an improved way to print circuit boards.
The researchers, from KAIST and the Korea Institute of Machinery and Materials, both in Daejoen, South Korea, have published their study on using tin nanoparticles in highly conductive ink in a recent issue of Nanotechnology.
Currently, most circuit boards are printed using multi-step methods such as conventional vacuum deposition and photolithographic patterning. However, these methods have disadvantages since they require a high processing temperature, involve toxic waste, and are expensive. Fabricating circuit boards using inkjet printing overcomes these limitations, and in comparison to the other methods is fast, simple, and inexpensive. Inkjet printing could be used for a variety of devices, such as RFID tags, LEDs, organic solar cells, organic thin-film transistors, and biomedical devices.
Recently, several studies have investigated different materials, such as polymers, carbon nanotubes, and metal nanoparticles, which could be used for the conductive ink. Although polymers and carbon nanotubes have advantages for printing on flexible displays, their conductivity is too low for them to be used for conductive ink materials. Metal nanoparticles have higher conductivity, and so are more suitable for conductive ink materials.
“The greatest significance of our work is that it is the first attempt to print conductive patterns with the Sn-containing conductive ink,” coauthor Yun Hwan Jo of KAIST told PhysOrg.com. “Several papers reported the synthesis of Sn nanoparticles for interconnection materials. However, no obvious melting temperature depression was observed due to the relatively large size and low uniformity of the Sn nanoparticles. In addition, there has been no report for fabricating conductive ink with Sn nanoparticles.”
In their study, Jo and coauthors synthesized a large amount of uniformly sized tin nanoparticles. As they explained, synthesizing tin nanoparticles that have a very small size is important because it leads to a lower melting temperature compared to that of bulk tin. For instance, while bulk tin melts at 232 °C, tin nanoparticles with a diameter of 11.3 nm melt at 177 °C. A lower melting temperature is beneficial because it means lower energy consumption, less substrate warping, and fewer thermal stress problems. The researchers also applied surface treatments to the conductive ink to decrease the resistance by a factor of 20.
“Two factors, cost and low temperature, are the advantages of the Sn-containing conductive ink,” Jo said. “Ag, Cu and Au nanoparticles are widely used to fabricate conductive ink. However, Au and Ag are expensive. And the melting temperature of Ag, Cu and Au nanoparticles is higher than that of Sn nanoparticles (177.3 °C, this experiment).”
By adding the tin nanoparticles to an ink solution, the researchers printed patterns of highly conductive ink from an inkjet printer. As the first demonstration of inkjet printing with tin nanoparticles, the results show that the new technique looks promising for printing various electronic devices that require conductive patterns.
“We are under study to fabricate conductive lines with conductive Sn ink via inkjet printing for flexible OLED devices,” Jo said. “We are optimizing the jetting conditions to draw complicated patterns using conductive Sn ink.”
More information: Yun Hwan Jo, et al. “Synthesis and characterization of low temperature Sn nanoparticles for the fabrication of highly conductive ink.” Nanotechnology 22 (2011) 225701 (8pp). DOI: 10.1088/0957-4484/22/22/225701
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Saturday, 16 April 2011
A team of researchers from the University of Plymouth, the Marine Biological Association of the UK and the Plymouth Marine Laboratory have conducted an exciting new study looking into the potential effect of climate change on marine life, and how marine animals may be able to adapt to future environmental scenarios.
Increasing anthropogenic (man-made) carbon dioxide (CO2) emissions over the last two centuries have led to a warming of the Earth’s atmosphere and a subsequent rise in sea surface temperatures.
In addition, around one third of this extra CO2 has now entered the planet’s oceans causing the seawater chemistry to change, a process called “Ocean Acidification”. These effects are predicted to worsen over the next few decades.
Consequently this recent study, led by Drs Piero Calosi and John Bishop, has looked at the potential impacts on sea life should the temperature and acidity of the oceans increase as is predicted to occur in the near and more distant future. It also investigated whether species have the genetic potential to adapt to the rapid changes currently occurring within the marine environment.
Dr. Calosi, from the Marine Biology and Ecology Research Center of the University of Plymouth, said: “Ours is the first study showing that marine animals may already possess genetic variation that will enable future adaptation, via natural selection, to falling pH and rising temperature.”
Their investigation focused on characterising growth and reproductive responses of different genetic individuals of a marine organism, to test the idea that some possess distinct responses to environmental changes.
Researcher Jennifer Pistevos said: “This is the first experiment comparing the responses of different genotypes of a marine animal to warming and ocean acidification scenarios predicted to occur in the years 2100 and 2300.”
Explaining the methodology, Dr. John Bishop, from the Marine Biological Association of the UK in Plymouth, added: “This was possible by using the bryozoan (sea mat) Celleporella hyalina, a colonial organism which grows by the addition of small male, female and feeding modules.
“Cuttings were taken from four original colonies to provide physically separate, but genetically identical, sub-colonies of each to use in the experiment.”
Overall, decreasing pH and increasing temperature caused a reduction in growth, with growth stopping all together at the highest temperature. In addition, colonies responded to decreasing pH by increasing their reproductive investment, specifically producing more males. This was interpreted as ‘reproductive bailout’ in colonies threatened with imminent death, promoting the rapid acquisition of reproductive success via releasing sperm.
Further observation by scanning electron microscopy revealed surface pitting of the calcified surface of colonies that were exposed to increased acidity.
Dr. Steve Widdicombe, from the Plymouth Marine Laboratory, said: “With our study we have shown that the genetic individuals tested here possess substantially different responses in growth, reproductive investment and sex ratio to the exposure to temperature, acidity and these two factors combined.”
This study is therefore relevant in understanding the likely responses of marine calcifying organisms, like the sea mat studied, to changes in ocean acidity and temperature. However, Dr. Calosi said: “Whilst it is good news that marine animals may have the potential to adapt to future global change scenarios, we still do not know how those genotypes able to persist under such scenarios will cope with subsequent environmental challenges.”
More information: The study was recently published in the international journal Oikos. More information on the paper is available at http://onlinelibra … 0.x/abstract
Provided by University of Plymouth-->
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