New inks made of phase-change nanoparticles that enable reduction of energy consumption have been developed, with various applications including in cooling and heating. The ‘nano-ink’ technology – patented by the University of Melbourne – is expected to enter a five to 10-year development period, to tailor it for specific markets, applications, and climates.
The outcome
A research team, led by Dr Mohammad Taha from the Faculty of Engineering and Information Technology at the University of Melbourne, has developed phase-change technology with applications in temperature control. In addition to improving thermal conditions in a range of situations (in buildings, homes and cars for example) and in products (such as electronic devices like laptops where heat build-up is an issue), the technology will contribute to a significant reduction in related energy consumption.
The nano-ink material is a proof-of-concept that’s versatile and adaptable. It can be laminated or sprayed onto surfaces, or added to paints and building materials, and its surfaces can be printed. The semiconductors it is made from can also be incorporated into clothing, regulating the wearer’s body temperature in extreme environments, or into the creation of large-scale, flexible electronic devices.
A different type of phase change material is already used to manufacture smart glass, but this new material will support the engineering of a broader range of products used in construction, such as bricks and paint.
This patented nano-ink has also been successfully demonstrated in flexible optoelectronics, where it acts as a photodetector that can detect wavelengths across a broad range of 0.4 to 20 micrometres at room temperature, at bend angles up to 100°. This has potential commercial applications in wearable sensors, curved displays, bendable solar cells, and curved focal plane arrays.
The need
Humans use a lot of energy to create and maintain comfortable environments in homes, buildings, cars and even in their bodies, with energy and how we use it the dilemma at the heart of the climate challenge.
Globally, humanity’s energy use represents by far the largest source of greenhouse gas emissions, and around two-thirds of global greenhouse gas emissions are linked to burning fossil fuels.
While the future of energy supply is in transferring to renewable sources that don’t release carbon, the need to reduce demand for energy will have to be part of the overall climate solution.
Developing the solution
Earlier research has explored one of the main components of ‘phase change materials’ – vanadium oxide (VO₂). These materials use triggers, like heat, electricity or some other type of stressor, which are used as energy sources for the transformation of the material to occur.
Vanadium oxides are highly promising materials for heat retardant coatings because they can undergo an insulator-to-metal transition (IMT) – basically acting as a switch, blocking heat beyond a particular temperature.
Until now, however, applications of phase change materials have been limited because they needed to be heated to very high temperatures for their ‘phase changing’ properties to be activated. This transition typically occurs at 68°C making it unsuitable for passive climate control in most household and industrial settings.
The researchers used their understanding of how these materials are put together to test how the IMT reaction could be triggered at more practical temperatures of around 30-40°C.
The team identified two ways to do this.
In the first, the properties of the material itself were changed to create a much more stressed compound. Adding in this stress created a more energised state, so the transformation process was triggered at lower temperatures.
The second way was to surround the molecule in glass nano-spheres, which introduced an external stress that further alters the energised state in the molecule, thereby activating its transformative properties.
(An analogy might be by pumping water to the top of a hill - you have a more energised dam to make electricity. Of course, on a macro sense no energy was created or lost, but the dam now is in a different energised state).
Publications
Taha, M., Balendhran, S., Sherrell, P. C., Kirkwood, N., Wen, D., Wang, S., Meng, J., Bullock, J., Crozier, K. B. & Sciacca, L. (2023). Infrared modulation via near-room-temperature phase transitions of vanadium oxides & core–shell composites. Journal of Materials Chemistry A, 11 (14), pp.7629-7638. https://doi.org/10.1039/d2ta09753b.
Balendhran, S., Taha, M., Wang, S., Yan, W. Higashitarumizu, N., Wen, D., Azar, N.S., Bullock, J., Mulvaney, P., Javey, A., Crozier, K.B. (2023).
Flexible Vanadium Dioxide Photodetectors for Visible to Longwave Infrared Detection at Room Temperature. Advanced Functional Materials, 2301790. https://doi.org/10.1002/adfm.202301790
Partners and Funding
This work was supported by the Defence Science Institute, an initiative of the Victorian Government. It was completed in laboratories across the Department of Electrical and Electronic Engineering, School of Chemical and Biomedical Engineering , School of Chemistry, and the School of Physics at the University of Melbourne, with assistance from the Materials Characterisation and Fabrication Platform (MCFP) at the University of Melbourne and the Victorian Node of the Australian National Fabrication Facility (ANFF).
First published on 8 June 2023.
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