Materials, nanotechnology and advanced manufacturing

Prelims

Natural mines are depleting, and a stone grown in a reactor is the same substance rather than an imitation of it. What separates the two is therefore not quality but provenance, which is where the trade argument sits.

• High Pressure, High Temperature (HPHT) synthesis mimics conditions in the Earth's mantle.
• Chemical Vapour Deposition (CVD) deposits carbon from a gas onto a diamond seed.
• The grown stone is cheaper than a mined one and easier to trace.
• Conflict diamonds still evade the Kimberley Process, which is part of the case made for the grown stone.
• India is investing in its own production and research.

Prelims

Jute's oldest market is sacking and its newest is civil engineering, where a geotextile woven from it is laid into the ground rather than over it. A fabric holding a slope until vegetation roots need not outlast the plants, so here biodegradability is the point rather than a defect.

• Jute geotextile protects embankment and riverbank slopes, aids vegetation on degraded land and goes under road and railway formations.
• The fibre comes from Corchorus capsularis, white jute, and Corchorus olitorius, tossa jute.

Prelims

A thermoelectric material turns a temperature difference straight into electricity, so a hot flue beside cool air is already a generator. The difficulty is that it must conduct electricity well while conducting heat poorly, which is why the search is for crystals whose lattice carries heat badly.

• The Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), an autonomous institute of the Department of Science and Technology (DST) in Bengaluru, found heat moving through thallium copper selenide (TlCu₅Se₃) in a wave-like way rather than as phonons, the lattice vibrations that normally carry it.
• That ultralow lattice thermal conductivity gives the crystal a zT of 1.7.
• Recovering electricity from industrial waste heat is the use claimed for it.

Prelims

A piezoelectric material gives out charge when it is pressed or bent, and the useful ones have been hard, inorganic and unwelcome inside the body. Peptides, the biodegradable building blocks of proteins, are none of those things, and the Centre for Nano and Soft Matter Sciences (CeNS), another DST institute in Bengaluru, has now made them piezoelectric.

• Piezoelectricity needs a non-centrosymmetric structure, one with no centre of symmetry, so that molecular dipoles line up instead of cancelling.
• In water alone the peptides form nanofibres with no response; one per cent of a co-solvent switches the property on.
• The co-solvent triggers chiral self-assembly into exactly that order, the chemistry unchanged.
• Implantable sensors, electronic skin and wearables powered by a heartbeat are the uses claimed.

Prelims

A graft has to fit the hole it fills, which is the argument for printing one patient by patient. A material put inside the body also has to be non-toxic and tissue compatible, and the best of them are resorbable, dissolving as new tissue takes their place.

• The Technology Development Board (TDB), a statutory body under the Technology Development Board Act, 1995, funded a company to 3D print patient specific bone grafts.
• It pays for a proven technology's move to commercial production rather than for the research behind it.
• The grafts are printed from hydroxyapatite, the calcium phosphate mineral of most bone and tooth enamel, and from beta-tricalcium phosphate, both bioceramics.
• Two printing routes were named: Digital Light Processing (DLP), which cures a whole layer with a projected image, and extrusion, which pushes a paste through a nozzle.