Author: Neal O’Hara, chief technical officer, Adama Innovations  Miniaturisation and the incorporation of nanotechnology into a wider range of industries have escalated in the last few years. The electronics and, particularly, the semiconductor industry have been scaling towards the nanoscale for the last 25 years. This has driven the development of very specialised and innovative manufacturing techniques, which often bear little resemblance to more traditional engineering enterprise. Major ongoing research programmes are focusing on the integration of these high-tech processes into more traditional manufacturing industry. Nanotechnology is an exciting field, offering a whole new paradigm in terms of material properties and functionality – for example, new materials such as nanoscale composites provide enhanced strength, while reducing weight. Adama Innovations is leading the way in bringing together expertise in materials science and high-tech fabrication to deliver the highest quality product for customers. When technology developed by the semiconductor industry is applied to the engineering of nanoscale features, various properties such as hydrophobicity can be targeted, leading to novel applications such as self-cleaning glass. Other applications of engineered materials at the nanoscale include hard-to-copy security features and cellular filtration devices. Of particular interest is the integration of novel advanced machining techniques to create injection moulds for cheap and disposal microfluidic chips for point-of-use diagnostics. The key engineering challenge in all the above is the incorporation of semiconductor fabrication techniques – particularly photolithographic patterning.

Photolithography vs nanotechnology

In the semiconductor industry, photolithography is used to define the length and width of a feature. While photolithography has served the semicon industry well to enable continuous miniaturisation, the technology is not very well suited to transfer outside chip fabrication to more traditional manufacturing processes. Apart from the high costs of the technology, including the necessity to use complex masks, it also requires pristine, flat surfaces due to the light processing nature of the technique (depth of focus, defects, etc.) To truly harness the power of nanotechnology, the manufacturing community need a technique that is free from these restrictions: one that has the flexibility to deliver nanoscale fabrication across different materials and geometries, and can integrate easily into the mass manufacturing techniques currently used, such as injection moulding. A patented invention, by Trinity College Prof Graham Cross, has already been deployed to address these challenges. It has been successfully commercialised with the help of Trinity College, Enterprise Ireland and Adama Innovations. Adama Innovations consists of a small team of industry experienced engineers who developed and optimised the technology. The technique allows a mask-free, ‘direct-write’ patterning down to the nanoscale, on multiple materials and shapes, including tools currently used in mass manufacturing. The technology is a simple two-step process: first the desired pattern is directly ‘written’ on the surface using a focused ion beam (FIB) tool, and then the second dry-etch step is used to etch away the unwritten material, to reveal the pattern in three dimensions. Using the technology, it is a simple exercise to directly create nano-scale features on a large variety of materials and objects –e.g. the Adama logo created below on industrial diamond (Fig 1.). [caption id="attachment_17648" align="aligncenter" width="640"]New Picture Figure 1[/caption] The first product that demonstrated the technology was the manufacturing of high-performance probes for use in atomic force microscopy (AFM). The AFM uses touch to provide an image of a surface at the nanoscale. Usually a silicon cantilever or beam with a sharp tip is scanned across a surface. A laser is reflected off the back of the cantilever into a photodiode detector. The laser spot will move across the photodiode as the cantilever responds to the surface. The output from the photodiode provides a computer-generated image of surface (see Fig 2). [caption id="attachment_17650" align="aligncenter" width="640"]New Picture Figure 2[/caption] The resolution of the image is governed by the tip radius and the tip wear. As the tip wears, the radius will increase and resolution will be lost. Therefore, choice of material for the tip is critical and diamond is the ideal candidate. The AFM industry already uses silicon probes coated in diamond, providing increased lifetime but at the sacrifice of resolution. By using the patented technology, a diamond-coated tip can be selectively implanted with gallium and the unwanted material can be removed using the dry plasma etch to reveal a sharp diamond tip (see Fig 3). This AFM product has now demonstrated significantly improved performance within the industry. [caption id="attachment_17651" align="aligncenter" width="640"]New Picture Figure 3[/caption]

FP7 Fabimed project

The company has also joined an EU-funded FP7 project called Fabimed. The main focus of the project is to integrate the expertise of all the partners to provide high-volume moulding and embossing techniques for length scales down to nanometer level . This can enable the cost-efficient fabrication of polymer products, for example microfluidics chips for use in point of care medical devices such as insulin testing. To achieve this, several machining techniques have to be integrated such as computer numerical control (CNC) machining , laser micromachining and the new patented technology into the same moulding die. The direct writing of the ion beam is controlled using a CAD/CAM software that is very similar to software used for tradition CNC milling. Therefore, the software control integration is very compatible. Figure 4 shows a stainless steel die fabricated by traditional machining techniques. This die is then coated with DLC and the Adama technology is then used to create micron and nanoscale engineered features into specific locations on the die. The SEM images show features created in the coated stainless test dies, and also the features subsequently replicated in biocompatible polymer. [caption id="attachment_17653" align="aligncenter" width="640"]New Picture Figure 4[/caption] This trend to miniaturise in the biotech area is also demonstrated in other major European research programs such as PolyNano and Cell-o-matic, which focus on polymer chips used for next-generation DNA sequencing, etc. In summary, the Adama platform technology has been proven in AFM probe fabrication and is now being deployed into mould fabrication, providing a mass-manufacturing solution for miniturisation, and bringing the benefits of the nanotechnology era to a broad range of fields beyond electronics.