February 2020 From the original article at Specialty Chemicals Magazine
One size does not fit all
Landon Mertz of Cerion Nanomaterials puts the case for nanomaterial customisation
TO BORROW FROM an old idiom, the field of nanotechnology continues to demonstrate that good things come in small packages. What sets nanomaterials apart from their larger sub-micron and micron-sized cousins is not simply their size per se, but the unique behaviours they exhibit at this smaller scale.
How these behaviours are leveraged forms the foundation for enhancing existing products, or creating new market-disrupting products. Getting nanomaterials to work properly in products, however, is a complex proposition. Further, ensuring that they will work consistently outside of a lab environment, when manufactured at scale, can be a frustrating and expensive exercise for those not practised in the art. At a time when exciting new innovations using the unique properties of nanomaterials are entering into the market, new adopters must bear in mind the critical aspects of nanomaterials and the degree of customisation required to ensure fitness of use, as well as the prerequisites for commercialisation.
The generally accepted definition of the nanoscale is where a material is 1-100 nanometers (nm) in at least one dimension. While this cut-off is somewhat arbitrary, as we approach these smaller sizes the surface area of a material increases exponentially, and new electronic properties are expressed. Compounding this, further manipulation of the material can often express unique and unexpected behaviours.
To demonstrate this, we can evaluate one of the most abundant metals in the periodic table, aluminium, which we all interact with daily. At bulk scale, aluminium is generally benign. However, at nanoscale, it becomes highly reactive and pyrophoric, which has allowed researchers to explore its use as a next generation solid-state propellant for rocket engines.
When tin is alloyed into the microstructure of an aluminium particle, the material can be made to off-gas significant quantities of hydrogen in the presence of water. Paired with a fuel cell, this allows for on- demand electricity generation, where 1 kg of nanomaterial has the same energy density as 13 kg of batteries. Finally, when the surface of aluminium is properly stabilised, it can be used as a cost- effective means to increase thermal conductivity in heat transfer fluids for products such as refrigerators, air conditioners and heat pumps.
This is just one example among many, where materials can be made to express a wide variety of commercially useful behaviours. Due to this, nanomaterials are considered to be an enabling technology, which, broadly speaking, has the potential to impact over 40 different industries and thousands of different products or systems.
Customisation in the lab
Cerion Nanomaterials, which specialises in designing, scaling and manufacturing metal, metal oxide and ceramic nanomaterials, frequently sees companies work with a material, only to conclude that it has limited utility in their product. An often-overlooked aspect of nanomaterials is that small changes to their composition, size, size distribution, phase and surface functionalisation can have outsized impacts on their performance.
By way of example, a customer asked us to create a nanomaterial to validate a theory that the properties of a rare earth element could be used to catalyse a proprietary chemical reaction. In this application, high oxygen storage capacity and rate of oxygen release were critical performance attributes. This was largely proven to be true, where the precise size of the material alone was a significant contributor to its performance (Table 1).
While a strong validation of the theory, the performance was insufficient for the intended application. However, with a small degree of exploration, we found that creating an alloy of the rare earth element with a small amount of a low-cost metal yielded a transformation in behaviour. Oxygen storage capacity increased by an impressive 1,100% over baseline, while the rate of oxygen release improved by 55%.
In another example, a nanomaterial was explored as a remediator of free radicals, which are a significant contributor to disease conditions such as multiple sclerosis and amyotrophic lateral sclerosis. Developed as an injectable therapeutic compound, the size of the material again played an important role. With a mean particle size of just 2.4 nm, the material was capable of passing through the blood-brain barrier and into the brain, where it could deliver its therapeutic effect. This is a distinction that fewer than 2% of neurological drugs have been capable of achieving. Equally important was a requirement for stabilisation of the nanomaterial to ensure biocompatibility in vivo, while not inhibiting the mechanism of action. After a small number of stabilisers were tested, a ratio of two stabilisers was chosen.
Animal testing showed that simply varying the ratio of each stabiliser exhibited results as far-ranging as premature death, high tolerability with marginally improved clinical scores, all the way to clinically significant performance with high tolerability.
Figure 1 – Fine tuning of biocompatible stabiliser ratio (A:B) to achieve safety & efficacy
Commercialisation from the lab
For decades, the nanomaterials industry has been plagued with bold statements around its disruptive nature, though only in the past decade has it begun to deliver on that promise. In order to transition a material to the commercial marketplace, three core competencies are required:
- Precise control over the design of the material
- Scaling up the quantity produced progressively, while preserving the desired material features and attributes
- Manufacturing consistently and cost-effectively at the required volumes
Generalising, more often than not those experienced in the art of nanomaterial science have expertise in one or two of these functional areas, with a select number of companies possessing all three. Cerion has sought to take this approach, by combining its own R&D and engineering expertise with industrially available equipment to enable us to pick the synthesis pathway with the best technical and cost fit for the customer.
There are multiple pathways to synthesise nanomaterials. Each method has unique advantages and disadvantages that must be evaluated against the technical outcome desired, design criteria for the material and the cost of using that method.
Table 1 – Measured performance of rare earth nanoparticles of varying sizes for oxygen storage and oxygen release
Typical methods include bottom-up approaches, such as precipitation, hydrothermal, solvothermal and high temperature reactions, and top- down processes, such as ball milling and high-energy milling. As is often the case, material providers will have strength in one synthesis method and attempt to force-fit this approach for material development and manufacturing.
When working with a nanomaterials firm, it is important that a customer understands, before experimentation begins, the relative advantages and disadvantages inherent to each method, so as to ensure that their research can transition effectively to a commercial product or system.
Another overlooked aspect of nanomaterials is the experimental design of the formula created in the laboratory and its ability to scale for manufacturing. The critical factors here include aspects like chemical yield, volumetric yield and processing conditions. For example, a formulation that makes the desired material but has a chemical yield of 50% or requires 1,000 kg of water to react 1 kg of material – is neither cost- effective nor practical to execute in a manufacturing environment.
To overcome this challenge, nanomaterial providers must use, and their customers must insist on, a ‘design for manufacture’ (DFM) methodology where development scientists, process engineers and business analysts collaborate with the researchers designing the material.
The goal here is to ensure the work performed in the lab will achieve successful scale-up and be cost-effective in the later stages of commercialisation. The DFM team must also evaluate the availability of raw material supply and cost, formula processability, tact time and energy inputs, to name a few.
These inputs must then be translated into manufacturability assessments and cost models that guide the researcher’s effort to meet the customer’s target price. Any effort below these standards runs the risk of a product development roadmap that takes longer, costs more to execute or fails late into the commercialisation process.
Big things with nano
The use of nanomaterials to create improved or disruptive products is virtually limitless. R&D into nanomaterials for commercial applications is currently enjoying a dizzying period of understanding, appreciation, and utilisation.
Users of these materials will be best served during their product development process by considering the customisation required to express unique behaviours that make product performance possible and the processes required to ensure that nanomaterials can be commercialised and transitioned to the marketplace.