Researchers at Purdue University have created a magnetic “ferropaper” that might be used to make low-cost “micromotors” for surgical instruments, tiny tweezers to study cells and miniature speakers.
The material is made by impregnating ordinary paper – even newsprint – with a mixture of mineral oil and “magnetic nanoparticles” of iron oxide. The nanoparticle-laden paper can then be moved using a magnetic field.
“Paper is a porous matrix, so you can load a lot of this material into it,” said Babak Ziaie, a professor of electrical and computer engineering and biomedical engineering.
The new technique represents a low-cost way to make small stereo speakers, miniature robots or motors for a variety of potential applications, including tweezers to manipulate cells and flexible fingers for minimally invasive surgery.
“Because paper is very soft it won’t damage cells or tissue,” Ziaie said. “It is very inexpensive to make. You put a droplet on a piece of paper, and that is your actuator, or motor.”
Once saturated with this “ferrofluid” mixture, the paper is coated with a biocompatible plastic film, which makes it water resistant, prevents the fluid from evaporating and improves mechanical properties such as strength, stiffness and elasticity.
Findings will be detailed in a research paper being presented during the 23rd IEEE International Conference on Micro Electro Mechanical Systems on Jan. 24-28 in Hong Kong. The paper was written by Ziaie, electrical engineering doctoral student Pinghung Wei and physics doctoral student Zhenwen Ding.
Because the technique is inexpensive and doesn’t require specialized laboratory facilities, it could be used in community colleges and high schools to teach about micro robots and other engineering and scientific principles, Ziaie said.
The magnetic particles, which are commercially available, have a diameter of about 10 nanometers, or billionths of a meter, which is roughly 1/10,000th the width of a human hair. Ferro is short for ferrous, or related to iron.
“You wouldn’t have to use nanoparticles, but they are easier and cheaper to manufacture than larger-size particles,” Ziaie said. “They are commercially available at very low cost.”
The researchers used an instrument called a field-emission scanning electron microscope to study how well the nanoparticle mixture impregnates certain types of paper.
“All types of paper can be used, but newspaper and soft tissue paper are especially suitable because they have good porosity,” Ziaie said.
The researchers fashioned the material into a small cantilever, a structure resembling a diving board that can be moved or caused to vibrate by applying a magnetic field.
“Cantilever actuators are very common, but usually they are made from silicon, which is expensive and requires special cleanroom facilities to manufacture,” Ziaie said. “So using the ferropaper could be a very inexpensive, simple alternative. This is like 100 times cheaper than the silicon devices now available.”
The researchers also have experimented with other shapes and structures resembling Origami to study more complicated movements.
The research is based at the Birck Nanotechnology Center in Purdue’s Discovery Park.
Writer: Emil Venere, (765) 494-4709, firstname.lastname@example.org
Neah Power Systems, Inc., a company developing fuel cell based renewable energy solutions, reported that it has signed documents with CyVolt Energy Systems to acquire all of its technology and assets. The cost of the acquisition would be covered by the company’s recently announced financing that management plans to use to acquire businesses that are expected to provide positive cash flows in the near term.
Dr. Chris D’Couto, President and CEO of Neah Power Systems, said, “Neah’s goals, as part of the recently announced funding, is to complete strategic acquisitions that complement Neah’s technology and meet our target of having commercially available products within the next 6 months. CyVolt meets these high standards.”
Neah intends to introduce the product, a hybrid fuel cell technology that recharges industry-standard lithium ion batteries, to the retail market within four to six months. Lithium ion batteries are the most common form of battery used in portable electronics. The product will produce ongoing power by “hot-swapping” additional fuel via cartridges or refills, thereby eliminating dependence on access to the electrical grid.
CyVolt Energy Systems is a Cleantech company developing fuel cell based portable power products for the consumer and military electronics market. CyVolt has developed a renewable fuel cell technology with the potential of significantly reducing development and downstream manufacturing costs. www.cyvolt.com
Neah Power Systems, Inc. (OTCBB: NPWZ) is developing long-lasting, efficient and safe power solutions for the military, industrial and consumer applications, Neah uses a unique, patented, silicon-based design for its micro fuel cells that enable higher power densities, lower cost and compact form-factors. The company’s micro fuel cell system can run in aerobic and anaerobic modes. The company is developing energy generation and storage solutions based on its patented technology. Further company information can be found at www.neahpower.com.
What if it were possible to go to the store and buy a kit to quickly and accurately diagnose cancer, similar to a pregnancy test? A University of Missouri researcher is developing a tiny sensor, known as an acoustic resonant sensor, that is smaller than a human hair and could test bodily fluids for a variety of diseases, including breast and prostate cancers.
“Many disease-related substances in liquids are not easily tracked,” said Jae Kwon, assistant professor of electrical and computer engineering at MU. “In a liquid environment, most sensors experience a significant loss of signal quality, but by using highly sensitive, low-signal-loss acoustic resonant sensors in a liquid, these substances can be effectively and quickly detected — a brand-new concept that will result in a noninvasive approach for breast cancer detection.”
Kwon’s real-time, special acoustic resonant sensor uses micro/nanoelectromechanical systems (M/NEMS), which are tiny devices smaller than the diameter of a human hair, to directly detect diseases in body fluids.
The sensor doesn’t require bulky data reading or analyzing equipment and can be integrated with equally small circuits, creating the potential for small stand-alone disease-screening systems. Kwon’s sensor also produces rapid, almost immediate results that could reduce patient anxiety often felt after waiting for other detection methods, such as biopsies, which can take several days or weeks before results are known.
“Our ultimate goal is to produce a device that will simply and quickly diagnose multiple specific diseases, and eventually be used to create ‘point of care’ systems, which are services provided to patients at their bedsides,” Kwon said. “The sensor has strong commercial potential to be manifested as simple home kits for easy, rapid and accurate diagnosis of various diseases, such as breast cancer and prostate cancer.”
Last January, Kwon was awarded a $400,000, five-year National Science Foundation CAREER Award to continue his effort on this sensor research. The CAREER award is the NSF’s most prestigious award in support of junior faculty members who exemplify the role of teacher-scholars through outstanding research, excellent teaching, and the integration of education and research. Kwon’s sensor research has been published in the IEEE International Conference on Solid-state, Sensors, Actuators and Microsystems and the IEEE Conference on Sensors.
Third-generation solar cells promise many advantages over their traditional counterparts, such as low cost, nontoxic materials, and improved efficiency, while also maintaining acceptable long-term stability.1Excitonic solar cells (either dye- or quantum-dot-sensitized) are strong candidates for further developments in this field.2
While dye-sensitized cells have a 20-year history of development and are now competitive with their poly- and amorphous-silicon counterparts in overall cell efficiency and stability, quantum-dot approaches are at the very beginning of their functional exploitation and have thus far performed poorly. However, intense development efforts are aiming to enhance the overall photoconversion efficiency single-crystal nanowires of transparent conducting oxides into photoanodes. Pioneering work suggested the possibility of obtaining a photoelectrochemical system in which electronic transport takes place along the single-crystalline backbone of 1D transparent nanostructures (see Figure 1).3–6 Thanks to the high electron mobility in single-crystal nanowires (approximately 100 times higher than in a polycrystalline network), this solution eliminates the drawback of polycrystalline photoanodes, where a single electron must pass thousands of grain boundaries before reaching the anode (with high recombination probability). In principle, this benefit could result in unprecedented cell efficiency, but to date only limited results have been obtained for nanowire-based cells.
Figure 1. Four different structures can be used as photoanodes in photoelectrochemical cells. (A) Polycrystalline network (traditional anode). (B) Polycrystalline nanotube. (C) Single-crystal nanowire array. (D) Network of single-crystalline nanowires and dispersed nanoparticles.
One of the most critical issues is the very limited specific surface of the nanowire bundle, which affects the optical density of the active layer. Engineered networks of mixed polycrystal powders and single-crystalline nanowires can merge the beneficial properties of both systems. These networks allow high optical density of the active layer, which results in nearly complete light absorption while maintaining a direct electron path (which minimizes recombination processes).7 Such systems can be profitably applied in both dye- and quantum-dot-based solar cells.
Figure 2. Scanning-electron-microscope images of three transparent conducting oxide materials integrated into photoanodes. (a) Traditional polycrystalline titanium dioxide (TiO2). (b) Zinc oxide (ZnO) single-crystal nanowire bundle. (c) Composite network of ZnO single-crystal nanowires and TiO2 polycrystals.
We have fabricated different networks of transparent conducting oxides with different morphologies for use as photoanodes. We considered three different systems (see Figure 2), including polycrystalline (traditional) titanium dioxide (TiO2), single-crystal zinc oxide (ZnO) nanowires (1.5μm thick), and single-crystal ZnO nanowires mixed with polycrystalline TiO2 (1.5μm thick). The almost similar electronic band structure of ZnO and TiO2 guarantees perfect compatibility from the point of view of electron transport, limiting the formation of detrimental electric fields which could affect electron mobility. We sensitized photoanodes using the commercial ruthenium-based dye molecule N719 (Solaronix), and the triiodide/iodide (I3−/I−) redox couple. Comparison of current-voltage curves of cells composed of ZnO nanowires versus the composite network (see Figure 3) indicates that the latter enhances the short-circuit current and cell efficiency. Nanonetworks reduced open-circuit voltage, likely due to higher recombination in the TiO2nanoparticles than in single-crystalline wires.
Figure 3. Current (j)-voltage curves of the dye-sensitized cells under 1 sun irradiation (airmass 1.5 global, 100mW/cm2). Solid line: ZnO nanowires. Dashed line: Network of ZnO nanowires and TiO2 nanoparticles. η: Efficiency.
Our work demonstrates the effectiveness of composite nanonetworks in enhancing excitonic solar-cell efficiency. Optimizing the material improved network efficiency compared to a bare nanowire bundle. We hope to fabricate dye- and/or quantum-dot-sensitized cells with high efficiency by simply enhancing the thickness of the active layer, which is our next step.
Cariplo Foundation, Program of Relevant National Interest (PRIN) 2007, National Institute for the Physics of Matter-National Research Council (INFM-CNR) seed project, and Greenvision Ambiente are acknowledged for partial funding.
National Research Council-National Institute for the Physics of Matter (CNR-INFM)
Saes Getters S.p.A. (Lainate MI, IT) received U.S. Patent 7,663,865 for its electrolytic capacitors which contain getter materials for sorbing harmful gases and liquids created by the capacitors during their use.If gases such as hydrogen and carbon dioxide are not properly absorbed, the operation of the capacitor can be adversely affected.Carbon nanotubes are among the getter materials.
Known electrolytic capacitors, e.g. EDLC supercapacitors (Electrochemical Double Layer Capacitor), are essentially comprised of an airtight housing, wherein electrodes typically formed of metal sheets are arranged, the electrodes being immersed in particular electrolytic solutions. The housing also contains gettering elements for sorption of substances harmful to the capacitors operation, and electrical contacts communicating the electrodes with the outside of the capacitor.
The electrolytic solutions are typically formed of a solvent and an ionic salt. In the EDLC case, for example, acetonitrile and propylene carbonate are frequently employed as solvents, while tetraethylammonium tetrafluoroborate is often used as a salt.
During use, these solutions can create harmful substances, often in gaseous form, which can damage the capacitors, possibly in an unrepairable manner. Another possible source of harmful gases can be due to the desorption of some materials used inside the capacitor.
Carbon dioxide, carbon monoxide, and hydrogen are among the most harmful gaseous species; while water, which is another particularly harmful species, is typically present in liquid form inside the electrolytic solution.
The problem of the sorption of harmful species inside the capacitors can be tackled by adding one or more sorbing elements mixed in the electrolytic solution, or by non-mixed sorbing systems. The use of materials with a gettering action mixed in the electrolyte can be accomplished by liquid sorbers.
Absorbtion materials are limited by the fact that the sorbing material, in addition to having the function of sorbing the harmful substances produced within the capacitor, must be compatible with the electrolyte, i.e., it must be completely inert with respect thereto, in order to prevent its sorbing properties from being jeopardized, or even worse, in order to prevent chemical species harmful to the correct operation of the capacitor being released as an effect of the reaction with the electrolyte. For example, the possible decomposition of the gas sorber could vary the electric conductivity of the electrolyte. Such a compatibility must be guaranteed by the sorber, even after the sorber has carried out its function by binding with the harmful species
Saes Getters’ device is made of a multilayer polymeric sheet, which is formed of an inner layer of polymeric material, containing particles of one or more getter materials for sorption of the harmful substances, and at least one protective layer of a polymeric material impermeable to the electrolyte. All of the polymeric materials are permeable to the harmful substances, say inventors Luca Toia and Marco Amiotti.
The getter material is at least one selected from non-evaporable getter alloys, unsaturated organic compounds, zeolites with a silver deposit, carbon nanotubes, palladium oxide, and cobalt(II,III) oxide; when the harmful substances comprise H2O, the getter material comprises at least one compound selected from alkaline-earth metal oxides, boron oxide and zeolites; and when the harmful substances comprise CO, the getter material comprises at least one compound selected from the following: cobalt(II,III) oxide, copper(II) oxide and potassium permanganate.