Biocatalytic Nanolithography: Nanofabrication of High Chemical Complexity Surfaces

Living organisms construct a tremendous variety of structures across a range of sizes, from large bones to microscopic cell components in order to carry out their life processes. Despite this variation in size, the assembly of all of these objects ultimately relies on the generation of molecules that are nanometres in scale (a billionth of a metre, or 1/100,000th of the thickness of a human hair). These biological "building blocks", composed of compounds such as sugars and proteins are produced by enzymes, the molecular machinery of all living organisms. In order to generate these complex larger structures, living organisms have developed a range of methods for moving these enzymes to specific locations where the structures need to be formed.

The ability to manipulate and study objects on nanometre scales is called nanotechnology, and is particularly interesting since at this size range, materials display new properties that are radically different from when they exist in their bulk form. By finding ways of harnessing these unusual properties, it is expected that they can be used to create entirely new types of technologies and devices. The basic idea of being able to move enzymes to particular locations as a means of controlling the construction of objects on this scale would therefore be extremely useful if it could be applied by us to assemble highly miniaturised devices, such as electronic components or circuits.

Harnessing enzymes for this purpose is particularly appealing since they are able to conduct a wide range of chemical reactions very efficiently and generate few unwanted by-products. Furthermore, they function under mild conditions and do not rely on rare or toxic materials. In contrast, many of the current techniques used in nanotechnology are derived from the electronics industry are not only limited in the types of chemistry they can achieve due to the harshness of the conditions under which they operate, but are also very power consuming.

Accordingly, the aim of this research project is to use enzymes that are able to promote the formation and deposition of materials to generate nanometre-scale patterns on a variety of surfaces. To achieve this aim, enzymes will be used together with an instrument called a "scanning probe microscope". This instrument uses miniature electrical motors to move a very sharp tip, the "probe" of the instrument, which is only a few nanometres wide. The instrument is also able to control the movement of this probe with nanometre precision. This ability to move and position the probe with such fine control makes it possible to use it to "write" patterns on surfaces. By attaching these enzymes to the tips of these probes, the chemical reactivity of the enzymes can be directed to deposit their materials as nanoscopic patterns. This new method of writing nanopatterns will be further facilitated by developing modified versions of these enzymes so that they will perform efficiently on a scanning probe. For example, they may be modified to deposit a wider range of compounds, or to be more resistant to damage so they may be used for a longer period of time before needing to be replaced.

The materials that are produced will then be tested to determine their electrical properties so that they can then be applied for the construction of miniaturised electronic devices. Furthermore, experiments will be carried out using many scanning probes writing patterns simultaneously, which will demonstrate how this new method of nanofabrication could be used for the mass production of chemically complex miniaturised devices.

This study will employ recombinantly engineered enzymes on scanning probes to develop a new nanolithography method. In doing so, it is intended that the method will enable the fabrication of organically functionalised nanopatterns that would be difficult to achieve using existing methods and be more sustainable. This research will therefore benefit a wide range of parties in academia and industry through the development of new biocatalysts and nanotechnology tools.

Firstly, this research would be relevant to scientists working in surface nanofabrication since current methods of manipulating materials at nanoscopic length scales are relatively limited in terms of the types of materials and surfaces that can be used. Furthermore, the two types of polymers proposed here are amenable to the generation of devices with potential applications in biosensing and electronics. This research would therefore be of interest to materials engineers that are attempting to harness new materials for the construction of miniaturised devices.

In terms of the enzyme engineering, the enzymes that will be developed here will give rise to new synthetic methods, as well as processes that are non-energy intensive and avoid the need for toxic feedstocks (i.e. more sustainable). This research will therefore benefit researchers in the area of applied biocatalysis through the development of new biocatalysts and insights into their application for the synthesis of polymers.

Beyond academic research, the development of this nanofabrication technique would be a significant step towards a low cost "desktop fab" that would allow access to a nanofabrication tool for a wider range of industries and researchers in the micro- (and nano-) machining sectors for the rapid production and prototyping of nanoscale devices, and would be an alternative to the current high cost, harsh and limited fabrication methods derived from the electronics industry.

Similarly, the ability to generate polymers with increased efficiency through the use of enzymes would lead to cost savings during the manufacturing of such materials. This is particularly important as silicones are widely used as components in a variety of areas, from consumer products (e.g. cosmetics, paints, detergents) to industrial applications (e.g. lubricants, coatings, sealants). The use of electrically conducting polyanilines, on the other hand, offers a route towards the production of electronic circuits that are not critically reliant on metals or semiconductors, which may rare or subject to supply insecurity.

More generally, the outcome of this research will contribute to the UK's position as a major participant in the fields of biotechnology and nanotechnology. Research in these areas will cultivate a new generation of scientists and enable the UK to better harness the potential economic and social benefits arising from the life science-nanotechnology interface, in the so-called area of "gold" biotechnology. The sustainable processes developed here will also reduce the environmental impact of human activity, enhancing the UK's green credentials and benefit the wider global community.

By the end of this grant period, we expect to have demonstrated the feasibility of using modified enzymes in conjunction with scanning probe microscopy for nanofabrication, allowing external parties to take our findings forward for wider applications in their respective areas. We will engage the potential end users of our research through publishing our findings in scientific papers and meetings and, where appropriate, through the exploitation of our intellectual property (e.g. patents, consultancy).