Engineers create leaf-inspired microreactor

INSPIRED by nature, researchers have developed a leaf-shaped photo-microreactor that they say could one day produce drugs at the point of use – such as malaria treatments in the jungle.

The device created by the team, which includes chemical engineers at Eindhoven University of Technology in the Netherlands, focuses the energy from sunlight falling on the ‘leaf’ and directs it to the ‘veins’ – or micro-channels running through the leaf – where it is used to convert the flowing reactants.

This development hinges on the novel idea of merging two technologies – embedding a flow reactor within a luminescent solar concentrator (LSC) lightguide. This lightguide captures solar light and directs it to a so-called reaction centre, mimicking the way plant leaves drive their own catalytic conversions of chemical species. Synthetic lightguides are already being used commercially, helping to boost the efficiency of photovoltaic power generation. The use of photochemistry has been opened up by the recent introduction of visible-light photoredox catalysis that has significantly expanded the scope of light-induced transformations, the researchers explain in their study.

Lead researcher Timothy Noël anticipates that the merged technology could provide a powerful tool for the sustainable and solar-driven continuous manufacturing of valuable chemical compounds including pharmaceuticals, agrochemicals and solar fuels.

“Using a reactor like this means you can make drugs anywhere, in principle, whether malaria drugs in the jungle or paracetamol on Mars. All you need is sunlight and this mini-factory,” said Noël.

To date, the team has proved the concept by using light and a methylene blue photocatalyst dissolved in with the reactants for the cycloaddition of singlet oxygen to 9,10-diphenylanthracene. Noël says the results of benchmark reaction surpassed all expectations: “Even an experiment on a cloudy day demonstrated that the chemical production was 40% higher than in a similar experiment without LSC material.”

The team says the polydimethylsiloxane (PDMS) that it used to create the leaf-shaped structure of the lightguide is well suited to making microfluidic devices because it can be easily shaped with both soft-lithography and print-and-peel techniques. The cost of the materials for each leaf was less than €1 (US$1).

Other advantages of the technology include that it uses diffuse light so does not need to be coupled with costly sun-tracking techniques and so could also find use at higher latitudes.

“It would be cool to see the boring-greyish piping of chemical plants of today being replaced with our colourful, solar driven photochemical photoreactors. Both the nice colour and the use of a sustainable energy source would help to alter the “negative” public image of the chemical industry,” said Noël. “We hope that this design will find its way into solar-driven photochemical transformations.”

Noël told The Chemical Engineer that the team is working to improve the stability of the leaf because PDMS swells in the presence of certain solvents, and is also seeking to improve the scalability of the production of the leaf.

Asked how long he expects it will be before he commercialises the work, Noël explained: “We did not protect this invention with patents. This was deliberate as I would like to get this on the market as soon as possible. Also my dream is that this would help third world countries in producing chemicals. They do not have a power grid to produce via the classical way with chemicals. With this device you do not need anything. True, we use pumps to introduce chemicals, but in principle you can power the pump with photovoltaics or you could also push the syringe manually!”

Angewandte Chemie: doi.org/f3tnwf