A team of scientists from Osaka University, The University of Queensland, and the National University of Singapore's Faculty of Engineering used tiny nanodiamonds coated with a heat-releasing polymer to probe the thermal properties of cells. When irradiated with light from a laser, the sens ... more
Good vibrations: Using piezoelectricity to ensure hydrogen sensor sensitivity
A team at Osaka University has invented a new process for creating high-precision sensing devices that respond to the presence of hydrogen gas. By carefully controlling the deposition of metallic nanoparticles on a silicon surface, the researchers were able to create a sensor that can detect low levels of hydrogen on the basis of changes in electrical current. This research may have important benefits as part of a switch to hydrogen-based fuels, which could power the zero-emission cars of the future and help fight anthropogenic climate change.
To fabricate a hydrogen sensor, the researchers deposited metallic palladium on a silicon substrate. The deposited palladium forms nanoparticles on the substrate, and they act like tiny islands that are excellent conductors of electricity, but, because they do not form a connected network, the current across the device is very small.
However, when hydrogen atoms are present, they are absorbed into the palladium nanoparticles, increasing volume of the nanoparticles, and then bridge the gaps between the islands. Eventually, a completely connected path is formed, and electrons can flow with much less resistance. In this way, even a tiny change in hydrogen concentration can lead to a massive increase in current, so the devices can be made very sensitive.
A significant challenge the Osaka researchers had to overcome was precisely controlling the gaps between islands to deposit in the first place. If the deposition time was too short, gaps between the nanoparticles are too wide and they would not be bridged even when hydrogen was present. Conversely, if the deposition time was too long, the nanoparticles would form a connected network on their own, even before hydrogen was applied. To optimize the response of the sensor, the research team developed a novel method for monitoring and controlling the deposition of palladium called piezoelectric resonance.
"Piezoelectric materials, such as a quartz crystal in a wristwatch, can vibrate at a very specific frequency in response to an applied voltage," senior author Dr. Hirotsugu Ogi explains. Here, a piece of piezoelectric lithium niobate was set to vibrate underneath the sample during the metallic nanoparticle deposition. The oscillating piezoelectric created an electric field around the sample, which in turn induced a current in the device that depended on the connectivity of the palladium network.
Then, the attenuation of the oscillation changes depending on the connectivity. Therefore, by listening to the sound (measuring the attenuation) of the piezoelectric material, the connectivity can be monitored.
"By optimizing the deposition time using the piezoelectric resonance method, the resulting hydrogen sensors were 12 times more sensitive than before," first author Dr. Nobutomo Nakamura says. "These devices may represent a step towards a cleaner energy future involving hydrogen."
- hydrogen sensors
The ongoing global pandemic has created an urgent need for rapid tests that can diagnose the presence of the SARS-CoV-2 virus, the pathogen that causes COVID-19, and distinguish it from other respiratory viruses. Now, researchers from Japan have demonstrated a new system for single-virion i ... more
Perovskites are a type of mineral and class of materials, and have been attracting a great deal of attention for their potential applications to technologies such as those used in solar cells. These unique materials have well-ordered structures and show many interesting properties that coul ... more
- 1analytica 2020 with very good results in the digital format
- 2Researchers find the favourite food of an enigmatic intestinal bacterium
- 3Spread of a novel SARS-CoV-2 variant across Europe in summer 2020
- 4How deadly parasites ‘glide’ into human cells
- 5analytica 2020: The world’s largest virtual trade fair for analysis, laboratory technology and biotechnology
- 6New cancer diagnostics: A glimpse into the tumor in 3D
- 7Midbrain organoids for automated chemical screening and disease research
- 8Artificial Intelligence has learned to estimate oil viscosity
- 9Nanopatterns of proteins detected by cryo-electron microscopy
- 10World record resolution in cryo-electron microscopy