Saturday, 29 November 2014
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Human-eye-inspired inkjet nozzle prevents clogging

Missouri University (MU) engineers have taken inspiration from the human eye to create an inkjet nozzle that doesn’t clog up.

‘The eye and an inkjet nozzle have a common problem: they must not be allowed to dry while, simultaneously, they must open,’ said Jae Wan Kwon, associate professor in the university’s College of Engineering. ‘We used biomimicry, the imitation of nature, to solve human problems.’

According to the university, Kwon’s invention uses a droplet of silicone oil to cover the opening of the nozzle when not in use, similar to the film of oil that keeps a thin layer of tears from evaporating off the eye. On the surface of the human eye, eyelids spread the film of oil over the layer of tears.

However, at the scale of the inkjet nozzle, mechanical shutters such as eyelids would not work, as they would be stuck in place by surface tension. Instead, the droplet of oil for the nozzle is moved in and out of place by an electric field.

To clear a clogged nozzle in most inkjet printers, a burst of fresh ink breaks through the crust of dried ink that forms if the machine isn’t used constantly.

Over time, this cleaning operation can waste ink; Kwon’s invention is intended to eliminate this.

Kwon said: ‘Other printing devices use similar mechanisms to inkjet printers. Adapting the clog-free nozzle to these machines could save businesses and researchers thousands of dollars in wasted materials.

‘For example, biological tissue printers, which may some day be capable of fabricating replacement organs, squirt out living cells to form biological structures.

‘Those cells are so expensive that researchers often find it cheaper to replace the nozzles rather than waste the cells. Clog-free nozzles would eliminate the costly replacements.’

Similarly, rapid prototyping systems used by engineers and product designers emit streams of liquid plastic through nozzles such as those on an inkjet printer.

The thick, sticky liquid used in the devices can make it necessary to replace the whole nozzle when they become clogged. These speciality printer parts can cost thousands of dollars.

MU engineering doctoral student Riberet Almieda worked with Kwon on the oil droplet nozzle cover and a paper documenting the discovery has been published in the Journal of Microelectromechanical Systems.


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