Tech Radar | What caught our attention outside the world of oil and gas this month
March 28, 2018
Scientists at Rutgers have developed a technique dubbed “4D printing” – creating a 3D printed object implanted with a hydrogel that changes shape in reaction to temperature.
In a paper published last month in Scientific Reports, the team illustrates a process for fast, scalable, high-resolution 3D printing of hydrogels, which remain solid and retain their shape despite containing water. In particular, the technique could be of use in the development of soft robotics and in flexible sensors and actuators.
“The full potential of this smart hydrogel has not been unleashed until now,” said Howon Lee, senior author of a new study and assistant professor in the Department of Mechanical and Aerospace Engineering at Rutgers University–New Brunswick. “We added another dimension to it, and this is the first time anybody has done it on this scale. They’re flexible, shape-morphing materials. I like to call them smart materials.”
Although hydrogels are well used, their manufacture has relied heavily on conventional production methods such as moulding and lithography.
Using a deposition method, the team printed resin to form a 3D object. The resin consists of the hydrogel, a chemical that acts as a binder, another chemical that facilitates bonding when light hits it and a dye that controls light penetration.
The hydrogel reacts precisely according to temperature. In temperatures below 32°C (~90°F), the hydrogel absorbs more water and swells in size. When temperatures exceed this level, the material expels water and shrinks.
Objects can be made as thin as a human hair or can be several millimetres long. The engineers also have found that they can grow specific areas of a 3D-printed object – creating and programming motion – by changing temperatures.
Working in partnership with research innovation project Luna Innovations, scientists at the US Air Force Research Laboratory (AFRL) and the Air Force Corrosion Prevention and Control Office supported the development of an improved system for coating material performance evaluations that will accelerate the screening, qualification and implementation of new corrosion-resistant aircraft coatings.
“By better understanding the corrosion performance of materials we put on an aircraft, we can help control corrosion costs and enable smart maintenance,” commented the team lead for corrosion and erosion in the Systems Support Division at the AFRL Materials and Manufacturing Directorate, Dr. Chad Hunter. “Corrosion maintenance costs are more than US$5 billion a year for the Air Force, so if we can better understand a material from the start, we can enable smart maintenance and ultimately reduce costs throughout the lifecycle.”
The new corrosion and coating evaluation system, CorRES, measures the ability of coatings to protect aircraft structures by using sensor panels that perform electrochemical measurements during corrosion testing. While conventional coating tests rely on visual evaluation at the conclusion of a test cycle, CorRES records corrosion rate data throughout a test. This enables researchers to know not only if a coating fails, but exactly when this occurs during a test.
This produces a far more comprehensive set of data for researchers. It can be used with sensing elements to measure free and galvanic corrosion, coating barrier properties and the effects of the environment on coating materials in a single testing platform, either in the lab or at outdoor exposure sites as well. CorRES platforms are now being used by US aircraft manufacturers, alloy producers, coatings material manufacturers, and the UK National Physical Laboratory.
Researchers have developed a stretchable, flexible patch that could make it easier to perform ultrasound imaging on odd-shaped structures.
A team from the University of California San Diego (UCSD) developed the system, publishing their results in Science Advances journal.
Conventional ultrasound probes have flat and rigid bases which struggle to maintain contact area when scanning across curved, wavy, angled and/or other irregular surfaces. This limits the deployment of the technology in crucial integrity environments.
“Elbows, corners and other structural details happen to be the most critical areas in terms of failure – they are high-stress areas,” said Francesco Lanza di Scalea, a professor of structural engineering at UC San Diego and co-author of the study. “Conventional rigid, flat probes aren’t ideal for imaging internal imperfections inside these areas.”
Gel, oil or water can be used to create better contact, but they can also disturb the signals received. Conventional ultrasound probes are also bulky, making them impractical for inspecting hard-to-access parts.
The UCSD team has thus built a soft ultrasound probe that can work on odd-shaped surfaces without water, gel or oil. The probe is a thin patch of silicone elastomer patterned with an array of small electronic parts connected by spring-like “bridges”. These contain piezoelectric transducers, and because the patch can stretch and bend, allow the patch to conform to irregular surfaces without compromising the signal.
The device is still at the proof-of-concept stage, and does not yet provide real-time imaging. However, the team has filed a patent on the technology. The researchers say they will now be working to integrate power and data processing into the probe to enable wireless, real-time imaging.
Researchers at the Max Planck Institute for the Science of Light in Germany have optically trapped and propelled a particle-based laser inside an optical fibre. Results were described in the Optical Society (OSA) journal Optics Letters, in a paper authored by Philip St J Russell and his team.
The new “flying microlaser” could enable highly sensitive distributed temperature measurements along the length of the fibre and could offer a novel way to precisely deliver light to remote and inaccessible locations.
The system is based on a “whispering gallery mode resonator” – a particle that traps and enhances certain wavelengths of light. It also employs hollow-core photonic crystal fibre – a length of fibre with a hollow central core unlike traditional solid optical fibres. This core is surrounded by a glass microstructure that confines light inside it.
The system was tested in a distributed temperature sensing experiment. The lasing microparticle was moved along two regions of the fibre heated to 22°Celsius above room temperature, and by measuring shifts in the lasing wavelengths emitted from the particle, the team could precisely detect changes in temperature. The sensor detected temperature changes of just under 3°C with a spatial resolution of a few millimetres.
“The spatial resolution of this distributed sensor is ultimately limited by the size of the particle,” said the Max Planck Institute’s Richard Zeltner. “This means that, potentially, we could achieve spatial resolution as small as several micrometres over very long measurement ranges, which is a huge advantage of our system compared with other types of distributed temperature sensors.”