Mass producing pocket labs


mix-id328072.jpg(Nanowerk News) There is certainly no shortage of  lab-on-a-chip (LOC) devices, but in most cases manufacturers have not yet found  a cost-effective way to mass produce them. Scientists are now developing a  platform for series production of these pocket laboratories.
Ask anyone to imagine what a chemical analysis laboratory looks  like, and most will picture the following scene: a large room filled with  electrical equipment, extractor hoods and chemical substances, in which  white-robed researchers are busy unlocking the secrets behind all sorts of  scientific processes. But there are also laboratories of a very different kind,  for instance labs-on-a-chip (LOCs). These “pocket labs” are able to  automatically perform a complete analysis of even the tiniest liquid samples,  integrating all the required functions onto a chip that’s just a few centimeters  long. Experts all over the world have developed many powerful LOC devices in  recent years, but very few pocket labs have made it onto the market.
Scientists at the Fraunhofer Institute for Production Technology  IPT in Aachen want to find out why so many LOCs are not a commercial success.  They are working with colleagues from polyscale GmbH & Co. KG, an IPT  spin-off, and ten other industrial partners from Germany, Finland, Spain, the  United Kingdom, France and Italy on ways to make LOCs marketable. Their ML²  project is funded by the EU’s Seventh Framework Programme (FP7), which is  providing a total of 7.69 million euros in funding through fall 2016.
“One of the main reasons LOCs don’t make it to market is that  the technologies used to fabricate them are often not transferrable to  industrial-scale production,” says Christoph Baum, group manager at the IPT.  What’s more, it is far from easy to integrate electrical functions into pocket  labs, and of the approaches taken to date, none has yet proved suitable for mass  production.
Microfluidic negative for structuring films
Microfluidic negative for structuring films. (© Fraunhofer IPT)
Platform for series production
The ML² project aims to completely revise the way pocket labs  are made so they are more suited to series production. “Our objective is to  create a design and production platform that will enable us to manufacture all  the components we need,” says Baum. This includes producing the tiny channel  structures within which liquids flow and react with each other, and coating the  surfaces so that bioactive substances can bond with them. Then there are optical  components, and electrical circuits for heating the channels, for example. The  experts apply each of these components to individual films that are then  assembled to form the complete “laboratory”. The films are connected to one  another via vertical channels machined through the individual layers using a  laser.
The first step the researchers have taken is to adapt and modify  the manufacturing process for each layer to suit mass-production requirements.  When it comes to creating the channel structures, the team has moved away from  the usual injection molding or wet chemical processing techniques in favor of  roll-to-roll processing. This involves transferring the negative imprint of the  channels onto a roller to create an embossing cylinder that then imprints a  pattern of depressions on a continuous roll of film. The electrical circuits are  printed onto film with an inkjet printer using special ink that contains copper  or silver nanoparticles.
Each manufacturing stage is fine-tuned by the researchers in the  process of producing a number of demonstrator LOCs – for instance a pregnancy  test with a digital display. These tests are currently produced in low-wage  countries, but with increased automation set to slash manufacturing costs by up  to 50 percent in future, production would once again be commercially viable in a  high-wage country such as Germany. The team aims to have all the demonstrators  built and the individual manufacturing processes optimized by 2014. Then it will  be a case of fitting the various steps in the manufacturing process together,  making sure they match up, and implementing the entire sequence on an industrial  scale.
Source: Fraunhofer-Gesellschaft

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Using nanoparticles to remove pollutants and contaminants from wastewater


201306047919620(Nanowerk News) The Fraunhofer Institute for  Interfacial Engineering and Biotechnology IGB and its European partners have  developed several effective processes for eliminating persistent pollutants from  wastewater. Some of these processes generate reactive species which can be used  to purify even highly polluted landfill leachate while another can also remove  selected pollutants which are present in very small quantities with polymer  adsorber particles.
Biological stages in wastewater treatment plants are not able to  remove substances such as drugs, found in the wastewater of medical centers, or  halogenated compounds and cyanides from industrial wastewater. This is why  antibiotics and hormonally active substances such as bisphenol A from plastics  manufacturing have already accumulated in the environment and can be traced in  ground water and even in some samples of drinking water. Such persistent  pollutants require a special purifying treatment to remove them from wastewater.  Our tests have shown that oxidative processes with hydrogen peroxide or ozone as  the oxidizing agent are especially effective.
It is usually necessary to adapt or combine various processes in  order to be able to degrade the many different components present in industrial  wastewater in an effective and efficient manner. The Fraunhofer Institute for  Interfacial Engineering and Biotechnology IGB runs a pilot plant in Stuttgart  for testing standard processes either individually or in any desired  combination. The IGB has added two new methods which generate reactive species,  especially hydroxyl radicals, efficiently. Hydroxyl radicals oxidize pollutants  into smaller, more degradable organic molecules or mineralize them completely to  carbon dioxide. In the first method, reactive molecules are generated  electrochemically in a combined anode/cathode process and in the second by means  of atmospheric pressure plasma. Neither method requires the addition of  additives.
Oxidative electrochemical treatment of landfill  leachate
Within the CleanLeachate project funded by the EU (grant  agreement no 262335), http://www.cleanleachate.eu), the Fraunhofer IGB has developed an  oxidative process which does not require additives and which is, thanks to its  electrochemical operating principal, suitable for treating extremely turbid  wastewaters. A consortium of six partners from five European countries is  currently treating highly polluted leachate from landfill sites with a combined  anode/cathode process, in which a membrane separates an electrolytic cell into  two separate chemical reaction areas. Top priority was given to choosing the  most suitable electrode material, especially for the anodes, where the hydroxyl  radicals are generated as reactive species when voltage is applied. The polluted  water flows past the anode where it is oxidized and is then pumped to the  cathode where the components are reduced.
The treatment is now being tested in continuous operation on a  landfill site in Czechia. This has lead to improvements such as the lowering of  the chemical oxygen demand and the overall nitrogen concentrations to below  legal limits and the fulfilment of wastewater regulations. To make the process  ready for marketing, a prototype was automated and made portable to test further  types of wastewater, while gathering experience and reliable data for further  optimization steps.
Open plasma processes for water purification
Another new approach for purifying water involves the use of an  atmospheric pressure plasma. A plasma is an ionized gas containing not only ions  and electrons but also chemical radicals and electronically excited particles as  well as short wave radiation. Plasma can be ignited by means of an  electromagnetic field e.g. by applying high voltage. The plasma glow is  characteristic and can be seen in the fluorescent lamps of neon signs used for  advertising purposes. In a technical sense, plasma processes have already been  used specifically for modifying and cleaning surfaces for a long time now.
Open plasma reactor
Open  plasma reactor. (© Fraunhofer IGB)
This principle is currently being applied by the partners of a  joint water plasma project, funded by the EU, entitled “Water decontamination  technology for the removal of recalcitrant xenobiotic compounds based on  atmospheric plasma technology”, grant agreement no. 262033, http://www.waterplasma.eu,  in which a plasma is used for purifying water in an oxidative process. The  result is a plasma reactor in which the reactive species formed in the plasma  can be transferred directly to the contaminated water. The reactor is “open” so  that the plasma is in direct contact with a flowing water film. The plasma  reactor is designed in such a way that a plasma can be ignited and maintained  between a grounded electrode in the form of a stainless steel cylinder within  the reactor and a copper network acting as high voltage electrode. To do so,  high voltage is applied. The copper network is on a glass cylinder which acts as  a dielectrical barrier, also shielding the reactor to the outside. Polluted  water is pumped upwards through the stainless steel cylinder in the center of  the plasma reactor. When the water flows down the outer surface of the cylinder,  it passes through the plasma zone between the stainless steel cylinder and the  copper network where the pollutants are oxidized.
In laboratory experiments, Fraunhofer researchers were able to  decolor a methylene blue solution completely within a few minutes. Cyanide was  also broken down effectively by 90 percent within only 2 minutes. Based on such  promising results, the process is now being tested on a larger scale. One of the  project partners is working with a demonstrator which can purify 240 liters of  contaminated water in one hour. The results will be used to continually optimize  the design of the reactor and its process controls. The ultimate aim is to bring  the reactor to market together with further partners from industry. The open  plasma process has a high potential due to the fact that there is no barrier  between the plasma, where the oxidative radicals are formed, and the  contaminated water.
Removing trace substances with selective adsorber  particles
Pollutants can also be removed effectively from wastewater with  selective adsorbers. An adsorption stage is particularly effective when  pollutants are strongly diluted, present in low concentrations or highly  specific. The process is also advisable when a wastewater component is degraded  to a toxic metabolite in biological purification stages. In such cases, it could  be better to remove the substance selectively by pre-treating the wastewater  before it reaches the wastewater plant.
To this aim, the Fraunhofer IGB has developed a single stage,  cost-effective process for producing polymer adsorber particles. In NANOCYTES®,  our patented process, functional monomers are transformed into small  nanoscopically sized polymeric adsorber particles, so-called specific polymeric  adsorber particles (SPA)[GDC1] , with a cross-linking agent. The selectivity of  the adsorber particles can be increased by adding the target molecules to be  removed from the water to the mixture. The trick works like this: once the  monomers have been polymerized, the target molecules can be removed from the  adsorber particles. They leave behind a kind of “imprint” which adsorbs the  target pollutants.
These particles possess a high specific surface area and the  particle surface is easily accessible without limitations. In addition this  approach offers a large flexibility in the design of the surface chemical  properties and the adsorption behavior. A large variety of different monomers  (mono-, bi- and trifunctional) can be used. They are selected on the basis of  physico-chemical properties such as solubility, miscibility and non-covalent  interactions with the target molecules. The particle properties can therefore be  tailor-made for special separation problems.
Fraunhofer researchers have been able to remove bisphenol A and  penicillin G selectively from wastewater. The adsorber particles are chemically  and thermically stable and can be used for a wide range of applications e.g. as  a layer in a composite membrane or as a matrix on packing materials. Once the  pollutants have been adsorbed, the adsorber particles can be regenerated and  re-used. An adsorption column is available at the Fraunhofer IGB for research  experiments.
Systems solutions for water supply and water  treatment
These innovative processes for water treatment complement the  Fraunhofer IGB’s portfolio in the fields of water purification and water  treatment. Together with further processes for water treatment and recovering  wastewater components as energy and fertilizing salts, the Fraunhofer IGB is  steadily optimizing wastewater treatment plants and improving DEUS 21, a system  for the semi-decentralized purification of household wastewater.
Source: McGill University

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New record for photovoltaic solar cells


 

 

 

 

 

28.09.12 – This week, EPFL’s Institute of Microengineering presented in Frankfurt “hybrid” photovoltaic cells with an energy conversion efficiency of 21.4%, the highest obtained for the type of substrate they used. This breakthrough will contribute to lower the cost of solar cell based installations.

In the medium term, an investment of only 2000 francs in photovoltaic cells would suffice to provide more than enough electricity for the consumption of a four people household. This promising scenario has been made possible by the innovations accomplished by EPFL’s Institute of Microengineering in Neuchatel. The team of prof. Christophe Ballif, director of the Photovoltaics Laboratory (PVlab), presented their work at the European Photovoltaic Solar Energy Conference and Exhibition that just took place in Frankfurt.

The PVlab specializes in thin film solar cells and has been interested for several years in “hybrid” technologies, better known as heterojunction technologies, designed to enhance solar captors’ performance. “We apply an infinitesimal layer – one hundredth of a micron – of amorphous silicon on both sides of a crystalline silicon wafer,” explains Christophe Ballif. This “sandwich” conception contributes to increase the sensors’ effectiveness.

For this assembly to be efficient, the interface between the two types of silicon requires to be optimized. Antoine Descoeudres managed to achieve this feat together with Stephaan DeWolf and their colleagues. They chose the commonest – and therefore cheapest – crystalline cell (called “p-doped silicon”), took care of its preparation and improved the process of application of amorphous silicon. They obtained a 21.4% conversion efficiency, which had never been achieved before with such type of substrates: nowadays, the best quality monocrystalline cells only attain an energy conversion efficiency of 18-19% at best. In addition, the measured open-circuit voltage was 726 mV, which constitutes a first-time accomplishment as well. Last but not least, they broke the 22% efficiency barrier on a less common substrate.

Close to the market
These results, validated by the Fraunhofer Institute for Solar Energy Systems (ISE) in Germany, will soon be published by the IEEE Journals of photovoltaics.
To bring these innovations to a stage of industrialization may only take a few years. This research was partly financed as a commission for Roth & Rau Switzerland, whose parent company, Meyer Burger, has already started the commercialization of machines built for assembling this type of heterojunction sensors. “Within three to five years, we expect to reach a production cost of 100 francs per square meter of sensors, estimates Stefaan DeWolf. In Switzerland, with the conversion efficiency achieved, such a surface will be able to produce between 200 and 300 kWh of electricity per year. “