28-Jul-2021: Nano-structured self-cleaning aluminium surface that reduces bacterial growth can be useful for biomedical & aerospace applications
A group of researchers have recently developed a nano-structured self-cleaning sustainable aluminium surface by utilizing a simple and environment-friendly fabrication route. It could have multiple applications ranging from biomedical to aerospace and automobiles to household appliances, and the process is easily scalable to industrial-level production.
Aluminium is a light metal, which has many industrial applications as it can be easily cast, machined and shaped. However, atmospheric degradation due to the accumulation of contaminants and humidity significantly limits its performance and sustainability. Besides, the leaching of aluminium also causes environmental and health-related issues.
To overcome these problems, Dr Harpreet Singh Grewal, Dr Harpreet Singh Arora and Mr. Gopinath Perumal, researchers from the Department of Mechanical Engineering and Dr Sajal Kumar Ghosh and Ms. Priya Mandal from Department of Physics of Shiv Nadar University, Delhi-NCR have jointly developed the nano-structured aluminium surfaces that show immense mechanical, chemical, and thermal durability restricting the corrosion and leaching effects. A Raman spectrometer obtained through the ‘Fund for Improvement of Science & Technology infrastructure’ (FIST) project of the Department of Science & Technology, Government of India, has been used to carry out this work. This result is reported in the Journal of Cleaner Production.
The researchers have developed a flake-like nano-structure on aluminium surface. This is achieved by heating the aluminium sample in water with a temperature maintained at 80oC for an hour, without using any chemical reagents and toxic solvents. The surface obtained by this facile and environment-friendly approach showed a complete wetting nature (ability of a liquid to spread over a solid surface). A coating of low surface energy hydrocarbon material on it converts it into a surface where a water droplet immediately rolls off the surface. This makes it useful for self-cleaning applications.
“This self-cleaning surface is stable over a wide range of temperature, from -80 to 350oC, improving its corrosion resistance property. In fact, it shows 40 times reduction in the corrosion rate when compared to the existing surfaces developed by other processing routes,” said Dr Grewal.
Dr Ghosh explains that because of their nanostructured morphology coated with hydrocarbons, these surfaces are capable of reducing bacterial adhesion and growth to a great extent and hence can be used in healthcare and medical devices, including dental implants and heart assistive devices.
24-Jul-2021: Indian scientists discover materials that self-repair mechanical damages
New materials may soon make it possible for damaged electronic components, such as in space crafts, to mend themselves. The materials recently developed by scientists can repair their own mechanical damages with the electrical charges generated by the mechanical impact on them.
Devices that we use daily often break down due to mechanical damage, forcing us either to repair or replace them. This decreases the life of the equipment and increases maintenance costs. In many cases, like in space crafts, human intervention for restoration is not possible.
Keeping such necessities in mind, researchers from the Indian Institute of Science Education and Research (IISER) Kolkata, teaming up with IIT Kharagpur, have developed piezoelectric molecular crystals that repair themselves from mechanical damages without need for any external intervention. Piezoelectric crystals are a class of materials that generate electricity when it undergoes a mechanical impact.
The piezoelectric molecules developed by the scientists called bipyrazole organic crystals recombine following mechanical fracture without any external intervention, autonomously self-healing in milliseconds with crystallographic precision.
In these molecular solids, due to the unique property of generating electrical charges on mechanical impact, the broken pieces acquire electrical charges at the crack junction, leading to attraction by damaged parts and precise autonomous repair. This research supported by the Department of Science and Technology, GoI via Swarnajayanti Fellowship to CM Reddy and Science and Engineering Research Board (SERB) research grants has been published in the journal ‘Science’ recently.
This methodology was initially developed by the IISER Kolkata team led by Prof. C Malla Reddy, a recipient of Swarnajayanti fellowship (2015) given by the Department of Science & Technology, GoI. Prof. Nirmalya Ghosh of IISER Kolkata, a laureate of the Society of Photo-Optical Instrumentation Engineers (SPIE) G.G. Stokes Award in Optical polarization 2021, used a custom-designed state-of-the-art polarization microscopic system to probe and quantify the perfection of the piezoelectric organic crystals. These materials with perfect internal arrangement of molecules or ions are called ‘crystals’, which are abundant in nature.
The IIT Kharagpur’s team, Prof. Bhanu Bhusan Khatua and Dr. Sumanta Karan studied the performance of the new materials for fabricating mechanical energy harvesting devices. The material may find application in high-end micro-chips, high precision mechanical sensors, actuators, micro-robotics, and so on. Further research into such materials may eventually lead to the development of smart gadgets that self-repair cracks or scratches.
29-May-2021: A natural dye extract may protect our eyes from harmful laser
Scientists have found that the natural indigo dye extracted from leaves of a plant of the bean family is capable of protecting human eyes from harmful laser radiation. It could be used to develop optical limiters useful in weakening the potentially harmful radiation and protecting the human eyes or other sensitive optical devices from accidental damage in an environment where such lasers are in use.
The blue dye extracted from Indigoferatinctoria or the famed Indigo plants has been used over the years to colour clothes and clothing materials. Although synthetic indigo dyes are now available, the natural variety also is in common use. It is extracted from the leaves of the plant, following standard protocols in scientific laboratories.
Researchers from the Raman Research Institute (RRI), Bengaluru, and Kensri School and College, Bengaluru, studied the optical properties of the natural Indigo dye and found that it can act as a device to protect human eyes from harmful laser radiation. The study, funded by the Department of Science and Technology, Government of India, was published in the journal ‘Optical Materials’.
The researchers extracted the dye and stored it in a refrigerator below 4º Celsius to preserve its natural properties. Their study on how much it absorbed light at different wavelengths of the electromagnetic spectrum showed that the absorption is maximum in the ultraviolet region of the spectrum, at a wavelength close to 288 nanometres, and in the visible region, close to 660 nanometres. The absorption is comparatively high for the green light as well. “Indigo absorbs light because of molecular absorption bands. The maximum absorption wavelength can vary over several nanometers depending on the dye’s solvent and concentration,” explains Reji Philip, professor at RRI and a co-author of the study. The absorption’s variation with wavelength indicated that chlorophyll, an organic compound that takes part in photosynthesis, is present in the dye.
The researchers wanted to study whether the organic dye showed additional absorption when the input light intensity is high.
The team found that when they increase the intensity of the laser pulse, the dye absorbs more light. That is, it is more opaque to higher intensity light. Scientists refer to such materials as an ‘optical limiter’.
Optical limiters are useful in weakening the potentially harmful radiation emitted by powerful lasers and protecting both eyes and sensitive optical instruments. “Making a prototype optical limiter using natural Indigo is the next logical step, followed by a commercially viable product,” Reji pointed out.