Graphene is a true marvel of material science. In this form of carbon, the atoms arrange themselves into two-dimensional layers. This gives graphene advantageous properties: it is electrically conductive, nearly transparent, and has high tensile strength. The material has been actively researched since its first synthesis in 2004, including at Empa. Its effects on humans and the environment were extensively studied in a EU 'Graphene Flagship' project with Empa's participation.
Now, Empa researchers are taking it a step further by applying the 'Safe and Sustainable by Design' (SSbD) principle to this novel material. 'Graphene is a good example because there have already been many studies and data on it,' explains Peter Wick, head of the Empa Laboratory 'Nanomaterials in Health'. 'We too have been working with this material for ten years as part of the “Graphene Flagship”.'
The fundamental ideas behind the SSbD concept are not new, the researcher further explains: The safety and sustainability of graphene were already central themes in the flagship project. What is new is the unification of these topics in the 'SSbD Framework', which is intended to enable sustainable and safe innovations for the industry.
Accordingly, the Empa researchers were not (only) interested in determining whether graphene is inherently safe and sustainable. 'We wanted to use the good data situation to test the application of the SSbD Framework and find out where and how it can still be developed and simplified,' explains Empa researcher Fiorella Pitaro from the 'Technology and Society' department.
A Name, Many Materials
The task is complex: thanks to active research and development over the past two decades, a whole range of related products known as graphene-like materials have been added to pure graphene. There is pure graphene as well as graphene oxide, reduced graphene oxide, 'few- layer graphene', which consists of several layers, and many more. Even these terms are not always clear and can themselves denote several slightly different materials.
This diversity is both a challenge and an advantage for the application of SSbD. 'We can use the data for each of these material subclasses to make statements about how the damage potential of a particular variant is related to its structure,' explains Wick. 'Since they often have similar functionalities, it is then ideally possible to use the safest form of graphene for each application.'
The way in which the material enters the human body is also crucial for statements about its safety: Is it inhaled or directly injected into the bloodstream as part of a medication? Does it enter our digestive tract through the food chain, or is it applied to the skin? 'To reliably assess the risk to humans, we need to know the application of the material,' says Wick. For it is the application that determines whether, how, and in what quantities exposure occurs.
Accessible and Reliable
'The tools and models used for assessments in the SSbD framework were mainly developed for chemicals,' says Fiorella Pitaro. While for chemicals the molecule structure primarily determines the properties, many more factors come into play for materials: the surface characteristics, the shape and size of the particles, the type of processing, and much more. Another goal of the Empa researchers, therefore, is to further develop the existing SSbD tools so that they can also be applied to materials.
The goal of SSbD is to promote sustainable and safe innovations. 'For it to be used by industry, especially SMEs, the framework must become more accessible and simpler', says Peter Wick. The statements it makes about the safety and sustainability of researched materials and chemicals should still be as reliable as possible. To reconcile these contradictory requirements, further research is needed – something the Empa teams are advancing in various projects.
As for the safety and sustainability of graphene, the experts are cautiously optimistic. In many areas and applications, the material seems to be safer and more sustainable than the carbon-based alternatives used today. However, this is not a carte blanche to release it into the environment without restrictions, they warn. 'We still don't know everything,' says Empa researcher Wick.
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