Big challenges for nanomaterials

As the nanomaterials sector increases production volume, there is a growing challenge in product quality assurance (QA).

This is a common and encouraging test for any material provider.

Material providers are one step in a larger system focused on delivering finished products to consumers.

In recent years this entire system has been focused on just-in-time delivery, reduced lead time, and best-cost production centres.

As such, one quality issue or ‘bad batch’ can send ripples through the supply chain.

The need for reliable quality is persistent across all nanomaterials providers.

Nanocomposix, a nanoparticle supplier, was actually started because of the founders’ trouble finding a reliable source for custom nanoparticles.

In the future, we will see continued pressure on graphene or carbon nanotube suppliers – some of whom are notorious for large lot-to-lot variations in quality.

Some chemical industries ensure quality through testing either various material properties (such as viscosity, conductivity, or density) or process conditions during production (such as vessel temperature, or mass balance).

The quality of a nanomaterial, however, is more complicated than bulk material properties.

Tough to test

Nanomaterial performance is based on material properties that are not readily tested using bulk material methods.

Changes in atomic structure, such as number of reactive sites or bonding, have dramatic changes in material properties.

For example, the reactivity of a nanoparticle can depend heavily on the nanoparticle shape.

Even two particles that have the same mass will perform differently.

Considering many nanoparticle suppliers can make up to a tonne of product a month, how do they ensure the correct shape is being produced when there is over 100 trillion nanoparticles in a single gram of material?

This is a difficult challenge even before considering other variables such as particle distribution, throughput rates, and contamination.

One of the most common QA techniques is end product sampling.

Sampling is the best way to get a clear picture of the end product performance.

Here, you can run a barrage of tests to characterise the final material properties.

However, sampling, is also recognised as the most limited form or quality assurance.

End product sampling also comes far too late in the process, when the most work has been done and the product is most valuable.

For nanomaterials providers, characterisation can seriously delay release and dramatically increase testing resource requirements.

The challenge to nanomaterial providers is not easy to bridge.

There are few standard quality control methods and equipment developed for in-process, large-scale nanomaterial production.

No two nanomaterials are created equal and a small change can severely impact the end performance for a customer.

As such, each company has to first determine the product ‘fingerprint’, then figure out how to reliably track that fingerprint over time.

This has been termed “nanoanalysis”, the process of determining properties of a target nanomaterial.

With little production-scale quality assurance equipment available, most companies are forced to employ QA methods using research-grade equipment.

This is neither cost effective nor fast enough to scale with production.

Some fortunate companies can employ custom in-line QA equipment, such as an integrated optical diffraction tool, to track material changes over time.

As an alternative, some laboratories offer nanoscale characterisation expertise or a QA expert on a contract basis.

The need for nanomaterial quality experts has been identified by the European Centre for the Development of Vocational Training (CEDEFOP) where they recognise the need to train quality assurance skilled professionals due to the high level of automation used in plants.

Quality at scale

Long term, a range of techniques need to be developed that ensure quality at production scale and throughput rates.

In-line optical or X-ray characterisation methods currently seem to be the most promising.

Also, surface analysis tools, such as scanning probe microscopy, are versatile and easily implemented.

Nanomaterials face a high quality bar when it comes to their customers.

Because nanomaterials are new and often intended to displace current bulk materials, nanomaterial providers are creating ways to specify customer performance guarantees.

Here, nanomaterial providers are not simply saying “we made the same stuff”, but instead they have to say “our product will act the same way for you”.

To reach this goal, companies are addressing these issues on a case-by-case basis.

Over time QA methods will catch up with production.

Remember the age-old phrase, “quality is remembered long after price is forgotten” - just like it did for steel and automobiles the same weighs true for nanomaterials.

Robert Ferris is elite product line manager at Emerson Process Management