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How to define complex materials in patent applications

It can be difficult to get a patent granted at the best of times — so what can you do when you need to provide a clear definition of a material that is near impossible to define?

Many patent applications have been filed over the last few years directed to graphene and graphene-containing products. However, what does the term ‘graphene’ actually mean in a patent claim?

Theoretically, graphene is a perfect monolayer of graphite. However, in practice, product material and devices do not generally comprise a perfect monolayer of graphite. The material may contain multiple layers and variable numbers of layers. The material may be doped, have impurities or various other functional components. Often, the user of the material may have little or no information about the specific type and composition of graphene material being used, other than the commercial source of the material. At best, characterisation of the material may only be partial. Furthermore, it may not be clear exactly which forms of graphene are required for a particular application.

Defining materials in patent applications

Patent claims must meet the requirements of novelty and inventive step. That is, they must define an invention which is new and non-obvious. Patent claims must also define an invention in a manner such that it is absolutely clear to a skilled person what the scope of the invention actually is — i.e. what would fall within the scope of the claims (and therefore infringe the patent) and what would not, and therefore be a legitimate work-around which is free to be used. The patent application as a whole must also describe the invention in sufficient detail such that a skilled person can put the invention into effect without undue burden, given the teachings of the patent application and common general knowledge in the field.

Problematic materials

While all of the above seems well and good, clearly defining certain materials can prove problematic. Small, organic molecules are relatively simple and easy to define by their molecular formula, or — more often — a generalised version of a molecular formula, which covers a family of compounds having the essential characteristics to enable the invention to work. However, it is more problematic to explicitly and clearly define materials such as crystalline materials, where the functional performance of the material may relate to crystal defect types, concentrations and distributions which are difficult or impossible to precisely define.

shutterstock_350946899-1copy.png#asset:1453A crystal dislocation defect, an example of a material which is difficult to precisely characterise

Measurement parameters and functional definitions

In light of the above, for certain materials, the only practical way to define a material may be in terms of its measured properties. In this regard, legal provisions allow for such definitions when it is not possible to more precisely define the invention and when the parameters can be readily tested to determine whether a material does (or does not) fall within the scope of a patent claim defined in this manner.

The type of measurement parameters which may be utilised to define a new material in a patent claim will depend to some extent on the type and envisaged applications of the new material and include mechanical, electronic, magnetic, thermal and optical characteristics, to name a few general types.

It is also advisable, where possible, to use well-established measurement parameters which can be readily compared with those of other materials in the public domain. This helps patent offices to assess whether a new material is novel and inventive over the prior art in the field. Patent offices are wary of claims defining new materials in terms of unusual measurement parameters, which are not easily compared with those in the literature for other comparable materials. They need to ask ‘is this actually a new material, or just a known material, defined in a new way?’ Defining a known material in a new way does not make the material itself novel.

It is also advisable to describe how the measurement parameters are obtained. If measured characteristics are used to define the material in patent claims, the method of making the measurement should be clearly defined — particularly where a measurement result can vary significantly depending on how the measurement is made. If this is not done, a claim could be deemed to lack clarity or, in extreme cases, lack sufficiency of disclosure, in that the invention is not sufficiently defined to put it into effect.

Example — a better diamond heat spreader

As an illustration of the above, I was lead counsel at a UKIPO hearing to determine the patentability of a diamond heatspreader invention, where the diamond material was defined in terms of Raman spectroscopy measurements (Patent Application GB1415353.0). The case has been cited in case law reviews as an example of what can be obtained in terms of parameterised measurement characteristics. The case in question related to a GaN-on-Diamond semiconductor structure. The patent claims focused on the diamond interface with the GaN and defined the diamond at the interface in terms of a Raman measurement. The claims were originally rejected as defining the material in terms of a result to be achieved, rather than clearly defining the product itself. I challenged the initial rejection and, at a hearing before a board of examiners, successfully overturned the rejection, obtaining grant of the patent. Arguments included:

  • (i) the Raman measurement characteristics were not a result to be achieved — the result to be achieved was a better heat spreader, which was achieved by modifying the manufacturing method, leading to a lower graphite content at the diamond interface which was measured via Raman spectroscopy
  • (ii) there was no other way of more clearly defining the invention
  • (iii) the measurement was readily testable
  • (iv) the Raman measurements were already used in the art to assess graphite content of diamond material.


While it can be difficult or impossible to answer all questions in relation to the characteristics and composition of certain materials, it is important to take due consideration of what is actually meant when specifying a material with a generic name in a patent claim. You must provide sufficient detail about the material in the patent specification to meet the requirements of clarity, support, and sufficiency. Materials should be characterised sufficiently such that a skilled person can select or manufacture a suitable form of the material which is capable of putting the invention into effect.

You might want to take a look at our dedicated materials sector webpage, or find out more about patents.

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