IISc researchers develop low-cost, drop-on-demand printing technique

Apart from traditional printing, it could also potentially be useful for 3D printing of living cells, ceramic materials, electronic circuits and machine components, the Bengaluru-based IISc said in a statement on Thursday. Printers used currently -- from inkjet printers to bio- printers that dispense living cells -- have a nozzle with a small opening to eject droplets.

A low-cost, drop-on-demand printing technique capable of generating a wide range of droplet sizes using a variety of inks has been developed by researchers at the Centre for Nano Science and Engineering (CeNSE) of the Indian Institute of Science (IISc) here. Apart from traditional printing, it could also potentially be useful for 3D printing of living cells, ceramic materials, electronic circuits and machine components, the Bengaluru-based IISc said in a statement on Thursday.

Printers used currently -- from inkjet printers to bio- printers that dispense living cells -- have a nozzle with a small opening to eject droplets. However, particles in the ink or a cell suspension can clog the opening, which limits the amount of particles or cells that can be loaded initially. Consequently, the thickness of the layer that can be printed is also limited, it was noted.

The new technique replaces the nozzle with a mesh covered with chemically treated nanowires that repel water, IISc said. When a large droplet impacts on this mesh, it bounces back. However, a small part of the liquid is ejected through the mesh pore as a jet that breaks to create a micro-scale droplet, which is then printed onto a surface.

Because of the short contact time of the impacting droplet with the mesh, the particles in the ink do not get a chance to clog the mesh pore, the researchers said. This allowed them to load the ink with larger quantities of nanoparticles, enabling printing of very thick lines in a single cycle. The mesh can also be easily cleaned and reused.

"The mesh costs only a small fraction of the nozzles that it replaces. This significantly reduces the operational cost when compared to conventional printing techniques," says Prosenjit Sen, Associate Professor in CeNSE and senior author of the study published in 'Nature Communications'. The researchers said they were able to demonstrate the use of this technique for various applications.

"Using drop impact printing, we could print 3D pillars of different sizes, an electronic circuit for semiconductor device applications, and bio-based droplet arrays for cell culture," said Chandantaru Dey Modak, first author and PhD student at CeNSE. "The capability to print a wide range of droplet sizes while using different kinds of inks for different applications makes this technique unique," he added.

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