21-Jul-2020: Researchers use metamaterials to enhance detection of defects in large structures
Periodic testing is required to prevent catastrophic failures in many engineering structures like buildings, pipelines and rails. High-frequency sound waves that travel in the bulk (bulk ultrasound) are widely used for non-invasive and non-destructive testing of structural materials.
Conventional bulk ultrasonic inspection is tedious and time-consuming, as it involves point-by-point assessment of structures, and this is especially challenging in large-scale assets.
To address this challenge, Indian Institute of Technology (IIT) Madras and University of Nairobi researchers have used metamaterials to improve detection of defects in large structures by Guided Wave Ultrasound.
In Guided Wave Testing (GWT), the sound waves are sent along the length of the structure rather than into the structure. This allows the waves to travel long distances.
Whereas, conventional ultrasound-based testing has to be done at multiple regions of the test material and is therefore quite difficult to be used with large objects such as train tracks, oil-pipelines and reinforcing structures of tall buildings, etc.
Metamaterials are artificially crafted materials with unique internal microstructures that give them properties not found in nature. The constituent artificial units of the metamaterial can be tailored in shape, size, and interatomic interaction, to exhibit unusual properties.
Acoustic metamaterials are useful in manipulating sound waves. The researchers used a metamaterial structure consisting of a series of periodically arranged channels.
With proper selection of channel size, length and periodicity of the metamaterial, the evanescent waves arising from scattering by a defect can be magnified by a process called Fabry–Pérot resonance.
Resonance is a phenomenon in which a wave, in this case, the ultrasound wave, is amplified due to a match in frequency between the wave and the frequency generated by the metamaterial.
In conventional bulk ultrasound-based testing, the sound waves are sent into the sample, say pipe or pillar, perpendicular to the item, and a detector calculates the time interval between the transmission and reception of the sound waves that are either transmitted or reflected. Sound waves travel at a uniform speed if the object is defect-free, but defects impede or deflect sound waves, which results in delays in reception.
GWT has poorer resolution than conventional ultrasound-based testing due to diffraction limitations. Thus, guided waves are only a long-range screening tool and must be used in conjunction with a testing tool with better resolution for accurate detection of defects.
29-Jun-2020: Eco-friendly Synthesis of Gold Nanoparticles from Antarctic Bacteria for Therapeutic Use
The National Centre for Polar and Ocean Research (NCPOR) and the Goa University (GU) have successfully synthesized gold nanoparticles (GNPs) using psychrotolerant Antarctic bacteria through a non-toxic, low-cost, and eco-friendly way. Through a study, NCPOR and GU have established that 20-30-nm-sized spherical-shaped GNPs could be synthesized in a controlled environment. These GNPs can be used as a composite therapeutic agent clinical trials, especially in anti-cancer, anti-viral, anti-diabetic, and cholesterol-lowering drugs.
The NCPOR-GU study revealed genotoxic effect of GNPs on a sulphate reducing bacteria (SRB). The GNPs displayed enough anti-bacterial properties by inhibiting the growth of SRB and its Sulphide production by damaging the genetic information of the DNA of the bacterial cell. Genotoxicity describes the property of a chemical agent that is capable of damaging the genetic information of DNA and thus causing mutation of the cell, which can lead to cancer.
Nanoparticles (NPs) have wide variety of potential applications in the fields of biomedical, optical and electronics research. Metallic NPs have been efficiently exploited for biomedical applications and among them GNPs are found to be effective in biomedical research.
Now, what is nanotechnology and nanoparticle (NP)? Nanotechnology is a technology that creates new and novel materials through controlled manipulation at a size range of 1 nm (nanometer) to 100 nm (1 nm equals to 10-9 m). And NPs are those materials that are at least one dimension smaller than 100 nanometres. NPs have a high surface-to-volume ratio and they can provide tremendous driving force for diffusion, especially at elevated temperatures. Sintering, i.e., coalescing into solid or porous mass by means of heating without liquefaction, can occur at lower temperatures at shorter time scales than larger particles. GNPs are melted at much lower temperatures (300 °C) than bulk gold (1064 °C). NPs have been found to impart various desirable properties to different day-to-day products. For example, GNPs are found to have greater solar radiation absorbing ability than the conventional bulk gold, which makes them a better candidate for use in the photovoltaic cell manufacturing industry.
GNPs have unique optical properties too. For example, particles above 100 nm show blue or violet colour in water, while the colour becomes wine red in 100 nm gold colloidal particles. They can thus be used of therapeutic imaging. GNPs also have unique physicochemical properties. Their biocompatibility, high surface area, stability, and nontoxicity make them suitable for various applications in therapeutic use including detection and diagnosis of diseases, bio-labeling, and targeted drug delivery. As nano-carriers, GNPs are capable of transferring various drugs made out of peptides, proteins, plasmid DNAs, small interfering RNAs, and chemotherapeutic agents to target diseased cells of the human body.
GNPs are also found to be useful in the electronics industry. Scientists have constructed a transistor known as NOMFET (Nanoparticle Organic Memory Field-Effect Transistor) by embedding GNPs in a porous manganese oxide as a room temperature catalyst to break down volatile organic compound in air and combining GNPs with organic molecules. NOMFETs can mimic the feature of the human synapse known as plasticity, or the variation of the speed and strength of the signal going from neuron to neuron. These novel transistors can now facilitate better recreation of certain types of human cognitive processes, such as recognition and image processing and have their application in artificial intelligence.
NCPOR and GU have resorted to environmentally acceptable green chemistry procedures to reduce gold ion to GNPs using psychrotolerant Antarctic bacteria. Moreover, they did not have to use synthetic chemical additives as stabilizing or reducing agents. Use of psychrotolerant Antarctic bacteria is found to have special advantages like mild reaction condition to reduce gold ion to Gold Nanoparticles (GNPs) with a good dispersion capability.
16-May-2020: ARCI scientists develop next-generation biodegradable metal implants
Scientists at the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) and Sree Chitra Tirunal Institute of Medical Sciences, Thiruvananthapuram both autonomous institute under the Department of Science & Technology (DST) have jointly developed new generation Iron-Manganese based alloys for biodegradable metal implants for use in humans.
Biodegradable materials (Fe, Mg, Zn, and polymer), which can participate in the healing process and then degrade gradually by maintaining the mechanical integrity without leaving any implant residues in the human body are better alternatives to currently used metallic implants which remain permanently in the human body and can cause long-term side effects like systemic toxicity, chronic inflammation, and thrombosis.
The ARCI team employed both conventional melting and powder metallurgy techniques in manufacturing of the new Fe-Mn based biodegradable alloys and stent having dimensions as Diameter: 2 mm, Length: 12 mm and Wall thickness: 175 µm.
Iron-Manganese based alloy Fe-Mn (having Mn composition of more than 29% by weight) is a promising biodegradable metallic implant which exhibits single austenitic phase (non-magnetic form of iron) with MRI compatibility.
The Fe-Mn alloy produced at ARCI exhibited 99% density with impressive mechanical properties and behaved as a nonmagnetic material even under a strong magnetic field of 20 Tesla. These properties are comparable to presently used permanent Titanium (Ti) and stainless-steel metallic implants. The alloy also showed a degradation rate in the range of 0.14-0.026 mm per year in the simulated body fluid, which means that the Fe-Mn alloy exhibits mechanical integrity for 3-6 months and completely disappears from the body in 12-24 months.
During the degradation process, calcium phosphate deposits on the implant due to local alkalization and saturation of calcium and phosphate, allow cells to adhere onto the surface to form tissues.
The team is making further efforts to achieve control in corrosion rates through alloying addition and surface engineering and to employ advanced manufacturing processes like additive manufacturing to realize complicated shapes.
Based on the impressive results, the ARCI team is certain that the newly developed Fe-Mn based alloys are suitable for biodegradable stent and orthopedic implant applications. In vivo and in-vitro studies are being planned at Sri Chitra Tirunal Institute of Medical Sciences by the team.