3D glassjet printer

A team of researchers from Southampton and Cambridge universities is developing very high temperature inkjet-style printers that will print with glass to produce 3D optical or electronic components.

A team of researchers from Southampton and Cambridge universities is developing very high temperature inkjet-style printers that will print with glass to produce 3D optical or electronic components.

The project is led by Dr Wei Loh, principal research fellow at Southampton’s Optoelectronics Research Centre, who explained: ‘Although we call this a glassjet printer, we are designing a multi-purpose high-temperature printing platform. If it can print glass, it can print other materials such as metals.’

Although inkjet printers started life printing ink on paper, the technology rapidly evolved to print a wider variety of materials, such as polymers for prototyping, manufacturing and research. The main constraint in using it for materials that are liquid only when very hot is that it typically works at room temperatures.

Loh said: ‘The polymers that it prints are typically low-temperature materials, and you have to apply quite a bit of polymer chemistry to get the right viscosity given that you have a temperature constraint,’ said Loh. ‘You can use materials that work with the existing printer, or you can change the printer so it works at higher temperature, in which case it relaxes a lot of constraints on the materials you can use.’

There already exist solder jet and metal jet printers for printed circuit boards. Solder jet printers are essentially modified versions of the inkjet printer that operate at between 200 and 300°C. There remains, however, the constraint on the basic inkjet printer design, which is the low-temperature piezoelectric actuator.

A printer that could print a wide range of materials such as metals and glass would be a highly versatile, useful 3D rapid prototyping tool for optoelectronics.

‘Nowadays if you want to make a prototype, you would make a mask, do a lithography, and etch,’ said Loh. ‘If you had a printer that could print the same materials, all you would need to do is program it to quickly give you the structure you need without the overhead costs.’

The applications could include making optical fibres and electronics — a CMOS gate is made from silicon dioxide, which is basically glass.

‘Glass can be easily made in certain geometries using conventional methods,’ explained Loh. ‘It can be made as a flat surface, you can use it to draw on a flat surface, or you can pull it into fibres with cylindrical geometry. Trying to make glass in other arbitrary geometries is not so easy.

‘What this printing platform will be able to do is make glass in a number of geometries, including spherical.’

An inkjet-style printer naturally prints out little droplets or tiny spheres. Sub-micron spheres produced by a glassjet printer could be used to accumulate into arbitrary geometry that is difficult to achieve by conventional methods. The spheres themselves could also be used as resonators or sensors, and there are emerging areas such as metamaterials that require complicated 3D structures for metal conductors and dielectrics. The glass could also be used to produce complex lab-on-a-chip technology.

Loh said that maintaining the necessary operating temperatures of 1,000°C or more would be one of the main challenges faced by the project. ‘But the advantage is that the materials you print at those temperatures are very stable and reliable at room temperature,’ he said.

When materials are cooled very rapidly, they can take on glasslike properties, as glass is a supercooled liquid. ‘If you took molten metal and cooled it rapidly, it would become like a metallic glass,’ said Loh, ‘so by cooling it rapidly we could have new and interesting materials.’ To be able to operate at the necessary high temperatures, the researchers will incorporate a furnace and develop a nozzle design that can withstand the high temperature. It will also need to be able to cope with any corrosive or reactive interactions with the glasses and other materials the researchers intend to use.

As the project is at a very early proof-of-concept stage, there are no industrial collaborators as yet, but those aware of the initiative include Kodak, other printing companies and end-user sensor developers.

The inkjet research centre in Cambridge is contributing printing expertise, modelling and theoretical work to help understand the droplet formation for these materials. ‘These materials such as glass and metals that we are intending to print have different properties from conventional inks, for example surface tension and conductivity of the materials,’ said Loh.

The government-funded project runs for three years. By the end, the researchers hope to have a prototype printing platform that works for glasses, metals and a range of other materials.

Berenice Baker