Tech Radar | What caught our attention outside the world of oil and gas this month
May 29, 2018
Opening new opportunities
Researchers from Swiss university ETH Zurich have developed valves small enough to control and separate individual nanoparticles.
These differ from traditional mechanical valves, in that they are opened and closed using electrical forces. “Mechanical valves can be miniaturised, but not as far as we would need for nanoscale applications,” noted ETH Professor Poulikakos. “If channels are thinner than a few dozen micrometres, they cannot be mechanically closed and opened with any regularity.”
Instead the team used channels etched into a silicon chip, with a diameter of 300 to 500 nanometres. In these, the team built nanovalves by narrowing the channels at desired valve locations using nanolithography and placing an electrode on both sides of the bottlenecks.
By activating the electrode in specific ways, the electrical field at this point is altered and a force will act on the nanoparticles present, pushing them through the bottleneck. This is how the valve is “opened”. Even particles in saline solution could be controlled using alternating fields.
Being able to capture nanoparticles in such a confined space could allow closer study under a microscope. The innovation could make it possible to build a complex nanochannel system with any number of controllable valves on a silicon chip. “By fine-tuning the electrical field at the electrodes, in the future it could be possible to use the valves as a filter, letting particles with particular physical properties pass through while blocking others,” added doctoral student Christian Höller.
The team hope to develop the technology, which could enable new lab-on-a-chip applications in materials, biomedicine and chemistry.
MIT researchers have been investigating ways to boost the performance of thermoelectric materials, with one group recently publishing a paper describing a material which could be five times more efficient, and generate twice the amount of energy, as the best such substances used today.
Research Laboratory of Electronics postdoc student Brian Skinner and Liang Fu, the Sarah W. Biedenharn Career Development Associate Professor of Physics at MIT, have studied a promising family of materials known as topological semimetals. They also sought to boost the materials’ performance by applying a strong magnetic field.
In theoretical modelling, the group calculated a figure of merit (ZT) for lead tin selenide – a value that tells you how close a material is to the theoretical limit for generating power from heat. The most efficient materials studied so far have a ZT of about 2, while Skinner and Fu found that under a strong magnetic field, lead tin selenide can have a ZT of about 10.
A material with a ZT equal to 10, if heated at room temperature to about 440°F, under a 30-tesla magnetic field, should be able to turn 18% of that heat to electricity, they reported.
This level of heat and magnetism is impractical in all but a handful of advanced laboratories, but the team says that materials with fewer impurities could produce better results with smaller magnetic fields. The discovery could open up new applications for heat recovery in industrial and commercial applications, such as power plants or vehicles.
Finding the (aqueous) solution
A study backed by the University of Maryland, US National Institute of Standards and Technology and the Army Research Laboratory (ARL) has produced a new kind of water-based zinc battery, suitable for use in extreme environments.
Although zinc battery chemistry has been used for centuries, it has fallen out of favour owing to the superior energy density of li-ion technology and the negative environmental effects of the acids used. However, li-ion batteries are flammable and also contain toxic electrolytes, meaning they are not suitable for all applications.
A solution proposed by the ARL researchers is to use lithium and zinc together with a water-based electrolyte, which precludes the possibility of fires. The team used an aqueous electrolyte based on zinc and lithium salts at high concentrations. According to their paper, published in Nature Materials, this electrolyte “not only enables dendrite-free Zn plating/stripping at nearly 100% CE, but also retains water in the open atmosphere, which makes hermetic cell configurations optional.”
This battery also overcomes other disadvantages of conventional zinc batteries, such as limited recharging cycles, dendrite growth and sustained water consumption (which previously meant the battery electrolyte had to be replenished regularly).
The team says that the technology could be used in consumer electronics, as well as in extreme conditions and safety-critical vehicles required for aerospace, military and deep-ocean environments.
The research team says this battery technology advance lays the groundwork for further research, and they are hopeful for possible future commercialisation.
"The significant discovery made in this work has touched the core problem of aqueous zinc batteries, and could impact other aqueous or non-aqueous multivalence cation chemistries that face similar challenges, such as magnesium and aluminium batteries,” noted ARL fellow and co-author Dr. Kang Xu. “A much more difficult challenge is, of course, the reversibility of lithium metal, which faces similar but much more difficult challenges.”
High definition, low power
University of Washington engineers have developed a new method for HD video streaming which does not require a power source. Instead, their prototype device passes moves the power-intensive functions onto the receiving device, e.g. a smartphone or computer, where the signal is processed.
The key to this is a technique called backscatter, through which a device can share information by reflecting signals that have been transmitted to it.
Rather than processing the video signal locally before transmission, pixels in the prototype camera are directly connected to an antenna, which sends intensity values via backscatter to a nearby smartphone. The phone, which does not have the same size and weight restrictions as a small streaming camera, then processes the video instead. The result is a much smaller HD camera, which does not require a bulky battery to support it.
For the video transmission, the system translates the pixel information from each frame into a series of pulses where the width of each pulse represents a pixel value. The time duration of the pulse is proportional to the brightness of the pixel.
In a demonstration, the team converted HD YouTube videos into raw pixel data, which was able to stream 720p HD videos at 10 frames per second to a device up to 14 feet away. The team has also created a low-resolution, low-power security camera, which can stream at 13 frames per second.
This technology has been licensed to Jeeva Wireless, a Seattle-based start-up founded by a team of Washington alumni researchers.