Mumbai | A study by IIT researchers has found that adding tiny, four-armed nanoparticles to certain plastics can significantly reduce their stickiness, making them easier to melt, mix and shape during manufacturing.

Mixing tetrapod-shaped nanoparticles - tiny particles resembling the four-armed concrete structures used as sea wave breakers - can make certain polymers flow more easily, discovered the collaborative study conducted recently by researchers from the Indian Institute of Technology (IIT) Bombay, IIT Madras, and IIT Kanpur.

"This study opens a pathway to potentially lower processing energy in the future, if we can mass synthesise precisely-shaped sustainable nanoparticles," said Prof Mithun Chowdhury, who heads the Lab of Soft Interfaces at IIT Bombay.

The inspiration for using tetrapods came during a walk along Mumbai's iconic Marine Drive, where these large concrete blocks are used to break sea waves and prevent beach erosion, he disclosed.

"This gave the inspiration of testing out tetrapods because of their unusual geometry. Nanoparticles of other shapes, such as spheres or rods, are known to increase viscosity rather than reduce it," noted Prof Chowdhury.

Researchers also ran control experiments with spherical and rod-shaped CdSe nanoparticles for comparison and noted that only the tetrapods improved flow, whereas the other shapes made the polymer more viscous and resistant to flow.

Prof Tarak Patra and Dr Sachin M B Gautham, both from IIT Madras, conducted the relevant simulation-based studies.

"The simulations showed the inner curvatures of a tetrapod create regions that long polymer chains find unfavourable to enter. This causes the lowering of the number of polymers around the nano tetrapod and thereby lets polymer chains slide past one another more easily," explained Prof Chowdhury.

The findings also suggested nanoparticle shape could potentially be used to tune how plastics flow.

"Many applications, like coatings, adhesives, or 3D printing resins, require specific viscosity for shape retention or load bearing. There are plenty of examples of nanoparticles increasing viscosity, but our study shows it can go both ways. Compact particles like spheres or roads can thicken materials, while branched geometries like tetrapods can make them thinner," said the IIT Bombay professor.

The team of researchers is currently exploring ways to scale up the process for preparing polymer-nanoparticle composites and adapt it to different types of polymers.

Key challenges remain, including large-scale nanoparticle synthesis and replacing toxic materials such as cadmium with more environmentally friendly alternatives, he stated.

"Future work will extend this to other polymers and more complex nanoparticle geometries. In the future, we aim to develop models, using AI or machine learning techniques, to predict the behaviour and flow patterns of polymer-nanoparticle composites based on nanoparticle geometry," Prof Chowdhury added.