Microwaving cells using graphene

Biological materials can be probed by their interaction with radio- and microwaves (MW), resulting in a specific signature, courtesy of their dielectric properties, i.e. how the materials respond to an applied electric field at a given frequency. This is already an established technique at the organ and tissue level; for tens of thousands and down to 10's of cells. I am using nanofabrication to bring the interaction between microwaves and biological materials to the single cell and few molecule range. This has been done for single cells using solely metallic waveguides.
What I am using to monitor the MW/biomaterial interaction at the nanoscale are 2D materials. They range from conductive, to semiconductors and insulators, while their main characteristic is, they can be peeled down to a single layer, even atomically thick, i.e. 0.3 nm, compared to an antibody which is ca. 10 nm in size. This results in the ultimate surface area to volume ratio and makes them very sensitive to changes in conditions on their surface.
The idea is to combine these layered materials and microwave biosensing in a single device. I am using graphene integrated into a self-designed and manufactured coplanar waveguide. A coplanar waveguide is a specific arrangement of conducting material, similar to a lengthwise cross section of a coaxial cable and allows for efficient travel of high frequency electrical signals, while confining the electric field to the vicinity of the central conductor/graphene. The ratios between strength and delay of the incoming signal, its reflection and the outgoing signal for each frequency changes due the electrical response of the surroundings close to the centre of the structure. In biological materials there are multiple mechanisms of this electric response, of different strength, at different frequencies, which then compose a spectral fingerprint allowing for the identification of the specific biological compound or tissue type. In order to bring the biological material into the centre of the waveguide, microfluidic channels are integrated into the design, allowing for controlled deposition and adsorption of the analyte on the sensor by controlling the flow and type of solution. The main advantage of graphene and related two-dimensional materials is that they are themselves modified by the environment in the solution, resulting in a strong signal even with minor differences. As these devices are quite small, they can be arranged in an array, each one functionalised for a different chemical, enabling multicomponent characterisation of bio-logical/-chemical on the same chip.
The initial focus of the PhD was designing and manufacturing the graphene waveguides and integrating them with microfluidics. The physical design was based on simulations performed using industry standard tools CST Microwave studio and Keysight EMPro. Graphene tends to form creases and tears, and the chemical process used to remove it from the growth substrate introduces impurities which change its chemical potential, conductivity and interaction with the environment. To obtain good sensitivity to the desired analyte and repeatability in the devices the process of depositing and patterning graphene on the electronics substrate had to be optimised, to minimise the above-mentioned effects. With the manufacturing process developed and the devices fabricated, the microwave waveguides can now be used for characterising the dielectric response. Graphene is functionalised with biological materials such as DNA, enzymes etc., which are non-covalently bound to the graphene surface. An analyte is then introduced in the solution, which if compatible with the functionalisation binds to it, changing the chemical potential of graphene. The binding of analytes is very specific for biological materials, leading the entire sensor to inherit it, allowing for determination of analyte concentrations and binding kinetics even in many-components solutions.

Our vision is to take graphene from a state of raw potential to a point where it can revolutionise flexible, wearable and transparent (opto)electronics, with a manifold return in innovation and exploitation. Such change in the paradigm of device manufacturing may revolutionise the global industry. The importance of graphene was recognised by the 2011 statement of the Chancellor of the Exchequer launching the initiative that lead to the funding of the Cambridge Graphene Centre, where the proposed Graphene Technology CDT will be based. The aim is take graphene and related materials from "the British laboratory" to the "British factory floor". Not only does our vision align with this mandate, but it also exploits and strengthens several key areas of national importance where the UK has recognised excellence, such as printed electronics, energy and RF & Microwave Communications. Thus, we will strive for both economic impact, by stimulating new UK-manufactured high-value products, and societal benefits, by utilising graphene in potentially many areas including security, energy efficiency and quality of life.
The beneficiaries of our proposal will be of course the cohorts of students that will be trained every year, but will extend more widely. Considering the private sector, we have already indentified tens of companies that will benefit from our work. To achieve the final goal of graphene-technology, and to ease the transition to commercialisation, we have strong alignment with industry needs and engage them as project partners of the CDT: Dyson, Novalia, Plastic Logic, Nokia, Toshiba, BAE Systems, Aixtron, PEL, Nanocyl, IdTechEx, Philips, Dupont, CambridgeIP, Polyfect, Agilent, Nippon Kayaku, Victrex, IMEC. Many more are also partnering with the Cambridge Graphene Centre, and even more are expected to join and benefit directly or indirectly from our work. We consider the civilian sectors of healthcare, telecommunications, energy and homeland security to be those in which applications based on graphene can make significant impact on society at large. There are also applications in defence, especially in secure communications and radars. This will foster competitiveness and enhance quality of life. In particular, the proposed CDT will be of prime interest to industries dealing with the following devices and applications: 1. Mobile communications, wireless sensor networks, including wearable devices. 2. Nano-structured materials for light and microwave energy harvesting. 3. Active and reconfigurable microwave, terahertz and optical materials, including advanced antenna applications for radar and communications.
Policy-makers, within international, national, local government will also benefit. If the vision of graphene as the material of the 21st century is fulfilled, there will be a need for its properties, benefits, applications and advantageousness compared to current technology to be known by the relevant public bodies. For example, any new policy on energy saving, or mobile communications may need to include a reference to the benefits, or limitations, of graphene-based devices.
Economic resilience and innovation require post-doctoral researchers and students trained in new areas. We will contribute to increasing the talent pool for the future graphene industry. The proposed doctoral training centre will provide unique training to students in various aspects of graphene technology: from graphene nanotechnology to energy, RF/microwave and (opto)electronics. This will develop many skilled researchers over the project lifetime, who will stimulate the sustainability of UK graphene engineering research and future commercialisation opportunities across a variety of sectors.