A microscopic ‘pen’ that is able to write structures adequately small to trap and harness light using a commercially available printing method could be used for sensing, lasers, biotechnology, and investigating the interaction between light and matter.
The printing-based technique, developed by researchers at the University of Cambridge in conjunction with the Hitachi Cambridge Laboratory, integrates high-resolution inkjet printing with nanophotonics – the study and harnessing of light on the scale of a billionth of a meter – the first time that this has been effectively showcased. The results are reported in the Advanced Materials journal.
Over the last 10 years, inkjet printing – the same standard technology that many people have at home – has progressed to the point where it can be used to print miniature devices, using a variety of printable materials, including living cells, as ‘ink’. This method is both simple and inexpensive, and it is extensively used in biotechnology and electronics.
“Most inkjet printers push the ink through the nozzle by heating or applying pressure, producing ink droplets about the size of the diameter of a human hair,”
Dr Vincenzo Pecunia, co-first author, former PhD student, postdoctoral researcher, currently visiting researcher at the University’s Cavendish Laboratory.
Pecunia’s research concentrates on printable optoelectronic materials for a variety of applications, and his team recently acquired a printer based on electrohydrodynamic jets: a long word that basically means a printer capable of ultra-high resolution printing. Rather than relying on heat or pressure, this type of printer applies a voltage to the ink, providing sufficient force to push it through a much smaller nozzle, creating ultra-small ink droplets – ten to a hundred times smaller than those created by conventional printers.
Thanks to an unintended meeting between Pecunia and co-first author Dr Frederic Brossard from the Hitachi Cambridge Laboratory, the researchers discovered that the new printer could print structures sufficiently small enough to be used in nanophotonics, which is Brossard’s area of research.
“Previous efforts to combine these two areas had bumped into the limitations of conventional inkjet printing technology, which cannot directly deposit anything small enough to be comparable to the wavelength of light,” said Pecunia. “But through electrodynamic inkjet printing we’ve been able to move beyond these limitations.”
The researchers managed to deposit ultra-small ink droplets onto photonic crystals. The ink droplets are small enough that they can be ‘drawn’ on the crystals on demand as if from an extremely fine pen, and locally alter the properties of the crystals so that light could be captured. This method enables the formation of many types of patterns onto the photonic crystals, at high speed and across a large area. Furthermore, the patterns can be made of all types of printable materials, and the technique is scalable, cost-effective, and the photonic crystal is reusable since the ink can be just washed away.
“This fabrication technique opens the door for diverse opportunities in fundamental and applied sciences,” said Brossard. “A potential direction is the creation of a high density of highly sensitive sensors to detect minute amounts of biomolecules such as viruses or cancer cells. This could also be a very useful tool to study some fundamental phenomena requiring very strong interaction between light and matter in new materials and create lasers on demand. Finally, this technology could also enable the creation of highly compact optical circuits which would guide the light and which could be modified by inkjet printing using the photonic crystal template.”
The research was funded partly by the Engineering and Physical Sciences Research Council (EPSRC) and the Science and Technology Facilities Council (STFC).
Frederic S.F. Brossard et al. ‘Inkjet printed nanocavities on a photonic crystal template.’ Advanced Materials (2017). DOI: 10.1002/adma.201704425