RSTV: SCIENCE MONITOR 9.8.2021 – INSIGHTSIAS

Self-repairing materials IISER Kolkata-IIT KGP:

• 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.
• 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.

Novel 3D Robotic Motion Phantom:

• Doctors in India may soon have the facility to simulate the lung motion of a cancer patient to help deliver focused radiation in the upper abdomen or thoracic region.
• Breathing motion is a hurdle for delivering focused radiation dose to the cancer tumour attached to upper abdomen and thoracic regions. The motion exposes an area larger than the tumour to radiation during cancer treatment, thus affecting tissues surrounding the targeted tumour.
• A focused radiation for a patient could be customised by simulating the lung movement of the particular patient and then orienting the delivery of the radiation so that it can be effective with minimal dosage.
• Before this is done on a human, its effectiveness needs to be checked on a robotic phantom.
• Recent technological development have resulted in state-of-the-art motion management techniques like-gating and tracking. Though there is incremental development in radiation therapy delivery of respiratory moving targets, the quality assurance (QA) tools have not been developed in parallel.
• For quantitative determination of the absorbed dose in an organ in the patient for a specific type of treatment procedure accuracy of respiratory motion management techniques, additional respiratory motion phantoms are required.
• A group of Indian scientists have developed a novel and cheap 3D robotic motion phantom that can reproduce the lung motion of a human during breathing.
• The phantom is part of a platform not only emulates the human lung motion as a patient is breathing but can also be used to check if the radiation is being correctly focussed on a moving target.
• The phantom is placed inside a CT scanner on the bed in place of the human, and it emulates human lung motion as it is irradiated during therapy. During irradiation, consistently high-quality images of advanced 4D radiation therapy treatments are obtained with minimum exposure of the patients and workers.
• Before the targeted radiation is delivered to a human subject, its effectiveness in focusing only on the tumor is checked with this phantom.
• The major part of the phantom is a dynamic platform over which any dosimetric or imaging quality assurance devices can be placed, and the platform can mimic 3D tumor motion by using three independent stepper-motor systems.
• This platform is placed on the bed where the patient lays down during radiation therapy. As phantom emulates the lung movement, a moving or gating window is used to focus the radiation from the radiation machine on the moving tumour.
• Detectors placed in the phantom help detect whether the radiation is localised on the tumour.
• The dose effectiveness is checked during therapy. The researchers are in the process of testing the system on a phantom. Once done, they will test it on human beings.
• This is the first time in India for manufacturing this type of robotic phantoms, and it is more affordable than other imported products available in the market as the program can be changed to produce different types of lung motion.
• The innovators are further trying to commercialize the product, which can be used in place of the overseas model that is very much more expensive and does not give access to the control software.

Size-selective deposition of nanocomposite coatings which can wear and friction of these dynamic systems:

• Several aerospace, defense, automobile, space devices need to reduce friction, wear, and tear to enhance the life of components. The usual route taken is to lubricate these dynamic systems, which add to the cost, complexity, and weight of these systems.
• A group of scientists at the International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI), an autonomous R&D center of the Department of Science & Technology (DST) have developed a process for size-selective deposition of nanocomposite coatings which can wear and friction of these dynamic systems.
• The scientists have found that nickel tungsten-based coatings with impregnation of particular sized Silicon Carbide (SiC) submicron particles using an economical and straightforward pulsed electroplating or electrodeposition process can provide an excellent combination of wear and corrosion resistance with the low friction coefficient and good oil retention capacity.
• The coatings developed by the ARCI group reduced friction more and could withstand corrosion due to salt spray better than many similar wear-resistant coatings available in the market.
• The coating could address the emerging need for coatings with low friction and wear. Nanocomposite coatings with hard particles inside a tough matrix result in the best combination of wear resistance and reduced friction.
• However, the size of reinforcement particles is a critical factor in deciding the friction characteristics. Too much variation in the size of reinforcement particles in composite coating results in premature failure of the coating due to stress concentration.
• Electrodeposition also called as electroplating, involves the metal parts to be immersed in an electrolyte bath solution, in this case, typically prepared by dissolving crystals of Nickel (Ni) and Tungsten (W) salts in a mix of distilled water and other additives.
• A direct current (DC) was passed through the solution, and the resulting reaction left a deposit of Ni-W alloy on the piece being plated. During electrodeposition, a diffusion layer was formed at the cathode surface due to movement and deposition of metallic ions in solution.
• For size-selective electrodeposition, pulse current (PC) electrodeposition – intermittent application of current was used in place of conventional direct current (DC) deposition. Pulsed currents of certain amplitude and duration helped in depositing coatings of desired properties, which would not be possible with conventional DC plating.
• The recent finding by Engineered Coatings group at ARCI shows that, by careful selection of pulse parameters, reinforcing particles of a given size can be selectively and uniformly deposited in a metallic matrix. In this process, during electrodeposition, only particles having a size equal to or less than diffusion layer thickness can be incorporated into the nanocrystalline coating.
• The size of the diffusion layer thickness is controlled by changing the duration of the electric current pulse during pulsed electrodeposition. The process is suitable to many other composite coatings requiring reinforcement for various applications, including fuel cells, batteries, catalysis, and so on.