Graphene Sensors for Food Allergen Detection

Exceptional electronic properties, surface sensitivity & selectivity, inferred by functionalisation, makes graphene ideal for sensor applications. Novel, generic, real-time monitoring sensor technology, based on chemically modified graphene transducers, will be demonstrated for food safety applications, detecting peanut (Ara h 1-9) allergens in food products. Trace quantities of nuts can be present in food processing plants at very low concentrations & can trigger an immune response in allergic individuals, ranging from hives to severe gastrointestinal & respiratory symptoms, & in serious cases - anaphylactic shock.

Where there is a possibility of cross-contamination, food producers are obliged to label products or recall incorrectly labelled products - costing industry millions (£5m/recall incidence) & producing negative publicity. Our sensor system, developed for in-situ smart monitoring of food & food processing units, would enable instant and low-cost allergen monitoring. Using chemically modified graphene, integrated into a packaged allergen sensor, for in situ monitoring would offer end-user Unilever a real breakthrough in monitoring for trace nut contaminants.

The sensor technology uses a graphene channel functionalised with a receptor molecule - capable of selective & specific detection of a particular allergen. Chemical functionalisation methods, for attaching antibodies to graphene, have already been developed by the consortium. This project will use antibodies targeted against peanut allergens as the receptors. Commercial sensor production requires large area, uniform, electronic-grade graphene - on an insulating substrate. UCAM
will develop "Transfer free" graphene on pre-patterned Ge could providing a step change in graphene electronics. In parallel, work will be performed on graphene grown on copper - transferred onto SiO2/Si wafers - mitigating risk by enabling device and functionalisation work to be completed prior to the availability of graphene/ Germanium.

Characterisation of these materials (NPL) is essential to providing uniform graphene with consistent and controlled electrical properties. NPL will analyse layer thicknesses, uniformity, defect densities and electrical performance following growth and also subsequent to chemical modification of graphene. PG will transfer existing graphene device fabrication process to large area CVD graphene on SiO2/Si & pre-patterned graphene on Ge wafers to fabricate graphene Chemical Field Effect Transistors. Chem-FETs comprise a graphene channel, patterned via lithography & subsequent oxygen plasma etch, between two metal (Ti/Au) contacts. Large area fabrication will reduce individual sensor costs. Based on current pricing wafer & processing costs of £1000 & using 4mm square chips, yields a cost of £2.22 per sensor. This could be reduced to £0.55 per chip by using a 2mm square chip. As the price of graphene comes down, this cost could be further reduced. Amine surface chemistry, developed under previous EPSRC grants [OJ Guy], will be used by PG to attach allergen-specific antibodies. Novel electrochemical diazonium functionalisation developed for antibody attachment to graphene will be used along with new plasma amine termination processes, before (a) amide coupling to the antibody & (b) blocking non-specific binding sites. Allergen binding to modified graphenes surface induces a gating effect, which can be electrically/electrochemically detected. PG and NPL will characterise functionalised graphene (XPS, I-V, CV, Raman, SKPM). PG's prototype sensors would ultimately be integrated into a model food processing unit at Unilever & used to detect trace quantities of allergens.

Chemically modified graphene sensors, developed by University of Cambridge (UCAM), ProGnomics (PG), National Physical Laboratory (NPL) and Unilever, will impact several major industries including: food processing, food security, health and beauty products, household products and environmental monitoring.

New device technology on pre-patterned Germanium, developed by UCAM / PG could provide a breakthrough for electronic grade graphene - as a "transfer free" method. This could also initiate developments with UK industry (IQE, SPTS) for volume production of graphene. In turn, this could provide a springboard for graphene electronics, by providing functionalised graphene (with a bandgap induced through chemical modification) on semi-insulating substrates. Development of characterisation methods for functional graphene, by NPL would impact the whole graphene industry -
from materials producers to applications end users. Characterised functional graphene would give confidence to the applications industry with regard to product quality, uniformity and performance.

Monitoring of food safety using functional allergen sensors would directly impact end user Unilever through increased sales - due to consumer confidence - and a wider, more flexible product range (facilitated by safe conversion of food processing equipment). Successful allergen monitoring could also have spin-off impact to the NHS - with potentially reduced numbers of cases of patients with anaphylaxis.

Unilever would also benefit from energy and water savings, from reduced cleaning requirements, reduced waste. Projected savings of 1.5% of the total plant energy use, with consequent reduction in CO2 emissions, and 5% of the site water consumption would have a considerable environmental impact.

Impact generated from sensor sales (through PG) would impact on all partners, through being stakeholders in the technology at all levels of the supply chain. UCAM and PG would benefit from exploitation of their intellectual property and licensing deals / royalties.

UCAM would generate impact from engagement and dissemination activities including conference and tradeshow presentations, high impact journal publications, publication in industry-focussed magazines, website postings, press releases and outreach events. Journal articles will be published in an open access journal to maximise readership where possible. UCAM and PG researchers have a track record of industrial, schools and public engagement activities and the project would promote micro and nanotechnology science via interactive demonstrations at Open Days and STEM
initiatives with local schools. Unilever will also participate in Schools events.

The project will also provide sustainability of the graphene activities at UCAM - generating some of the first graphene application products. This will also benefit the graphene industry as a whole - providing a case study for successful graphene products.