Turning food waste into nano-fibres

Saeed Mohan, a post-graduate student at the University of Reading, has been working on a project to research various fibres in order to improve their mechanical properties, funded by the European Union in a collaborative project (under EU FP7) with a variety of other partners who are involved in producing materials for use as polymers and in their subsequent commercial exploitation. Polymers are long chains of repeated unit molecules (called monomers) which are particularly useful as they can be braided together to make a strong and lightweight material, like carbon fibre.

The simple way of describing Saeed's method is that it works like a candy floss machine. The polymer is dissolved in a solvent, at a concentration viscose enough to produce fibres. The motors drive the extrusion drum with its fine apertures and the fluid is centrifugally spun into fibres as it is extruded. As part of this process the solvent is naturally spun off. Saeed first contacted Maxon Motor UK when he was looking for a high-speed DC motor with a DC motor controller, capable of variable speed, in order to test his theory at different centrifugal forces with different viscosities.

Saeed says: "I liked the idea that Maxon had a motor and controller package that made it fairly simple to get started. I used the brushless EC-max 30 motor, together with the ESCON controller as I was looking for up to 10,000 RPM (the ESCON is capable of 150,000 rpm). The ESCON Studio software (escon.maxonmotor.com/Downloads/en/ESCON_Setup.exe) was easy to download and Mark gave me some initial help with using the ESCON 50/5."

Mark Gibbons, Technical Engineer with Maxon Motor, explains: "We started with a mass of 300g at 10,000 rpm and we tested the concept with his prototype cylinder. Once we were both happy about the application and the appropriate use of the motor and controller, I offered the motor at a reduced price as we often do when supporting educational projects."

The first stage of the project involved a large cylinder, vertically mounted. The cylinder was filled with solution and spun up to speed, which produced a lot of waste material during the acceleration phase where the centrifugal extrusion force was not constant or high enough. Saeed focussed on reducing the waste and increasing the yield, and his early tests showed the feasibility of the concept. After further discussions Mark came up with an approach: a motor with a hollow shaft where the solution could be constantly gravity fed and the flow would not begin until the cylinder was up to speed. The ESCON has a speed monitor output that can be used to keep the valve shut until the required speed was reached, enabling the continuous production of fibre with minimum wastage.

Environmentally friendly products

Saeed is particularly interested in using the spinning process to produce high-quality fibres from waste product from food processing. Polymeric materials make up a large portion of food materials but are not always used as such. Different polymer materials can be sourced from specific food waste; apple pulp, being fibrous, is currently a throw-away product after the manufacture of apple juice, but it could be generated into polymers that could easily be constructed into useful environmentally friendly products.

For the future Saeed is looking at larger-scale production of the nano-fibres. Fine polymer strands can be used for more intricate applications or the ability to weave more complex materials for better strength and compactness. Such materials can be used to produce scaffolds for tissue regrowth after serious damage to tissue or even bone, or as ultrafine filters for respirators. The lightweight polymer could also be used in the manufacture of aircraft, racing cars and prosthetics, all areas that are constantly looking to reduce weight in order to be more competitive.

To learn more about Maxon's high-speed DC motors and controllers, please visit www.maxonmotor.co.uk.