Self-care Materials

“We really want to control the materials so that we can have delivery on demand. That’s why we call the Challenge self-care materials—the materials should be able to react autonomously depending on changing conditions in the environment.” René Rossi, Empa

Fibre-shaped substances have large surface areas compared to their mass—this gives them considerable scope for interacting with the surrounding environment.

René Rossi, head of the Laboratory for Protection and Physiology at Empa, and Fabien Sorin, head of the Laboratory of Photonic Materials and Fibre Devices at EPFL—the principal investigators behind the CCMX Materials Challenge “Self-care Materials”—hope to exploit this property to develop fibre-based controlled substance delivery systems for use in fields as diverse as health care, textiles and packaging.

That is, teaming fibre-based systems with so-called smart polymers that react to external triggers such as temperature, pH, humidity or pressure could provide delivery on demand. This may result in items such as packages that can release antioxidants to preserve food longer; textiles that deliver drugs through the skin at specific locations, at a specific rate and specific time; in-body structures that can release anti-inflammatory drugs, or even fibrous tissues that can generate growth factors.

“When we look at the literature, there are a lot of polymeric delivery systems, but they’re usually capsules or maybe some gels, and not many of them have really constituted a breakthrough in industry,” Rossi said. “We think this is maybe due to a large part to processing problems. We have developed advanced fibre technologies and would like to use a different approach.”

Today’s delivery solutions are generally built around small passive capsules that release substances as they degrade or diffuse. There is little control over how the substances spread, where the delivery occurs, or at what time and rate. What’s more, the systems are difficult to activate, there is limited scope for tuning different properties during processing, and they are not particularly well suited to the new types of surfaces with which they need to interact, notably in the fields of health care. Alternative processing approaches could help solve these problems.

The technologies in question involve Rossi’s field of solution spinning and Sorin’s field of multi-material thermal drawing. Solution spinning involves producing fibres by dissolving polymers in solvents and extruding them inside coagulation baths containing non-solvents or into a heated chamber of air, depending on the type of spinning. It also includes the use of electrospinning technology enabling the generation of very small fibres with drug release abilities.

Fairly recent developments mean that the techniques can now be used to make hybrid structures that have controlled geometries that can impact the functionality of the material.

Sorin’s “multi-material” fibre drawing technique refers to integrating metals, semi-conductor materials, insulator materials, functional polymers or polymer nanocomposites with various properties into fibres using preform-based processing methods. Researchers can integrate multiple functional components into one fibre or assemble large-scale two and three-dimensional geometric constructs made of many fibres.

These two approaches—scalable, low cost, and giving researchers the ability to tailor micro and molecular structures with high precision—may lead to a new class of multimaterials micro-structured fibres integrating innovative biodegradable polymer architectures. Fibres have the additional advantage that they can be integrated into a variety of supports such as textiles, scaffold, tissues and even thin packaging films.

The team will investigate the interplay of viscosity, adhesion, surface tension and feature sizes, all of which are essential to achieving the right fibre performance and architecture. They will also look at how fibres interact with and behave in their environments through advanced characterisation techniques.

“There have been a lot of improvements in the way fibres are processed and in the types of materials, architectures and geometries that we can integrate inside them to have both active and passive control of delivery,” Sorin said. “We want to leverage these new developments we’ve both been leading in our research areas for the field of controlled delivery.”

The researchers say one important aspect of their work is simply bringing more materials science to the field of delivery. Until now, it has been dominated by pharmaceutical and medical research, that is, by biologists whose expertise does not lie in the materials science behind drug delivery or processing. Various elements of materials science can be used to integrate complex functionalities into the resulting systems and such expertise is also needed to investigate, for example, how electrospinning or thermal drawing processes affect the morphology and structure of the polymer fibre produced, and how these parameters affect in turn the kinetics of, say, drug release.

“We really want to control the materials so that we can have delivery on demand,” Rossi said. “That’s why we call the Challenge self-care materials—the materials should be able to react autonomously depending on changing conditions in the environment.”

A number of industrial partners from the fields of health care, chemicals and textiles have joined the project, as have collaborators from the broader ETH domain. The consortium is a good indicator of the broadness of the interest in this field, which could develop products that monitor and release substances, preserve products or treat individuals.

Text by Carey Sargent (March 2016).