Tien-Chun Wu1 Andrea De Luca2 Thomas Albrow-Owen1 Guohua Hu1 Florin Udrea2 Tawfique Hasan1

1, Cambridge Graphene Centre, University of Cambridge, Cambridge, , United Kingdom
2, Department of Engineering, University of Cambridge, Cambridge, , United Kingdom

Early diagnosis of diseases with smartphone/wearable devices is at the forefront of intelligent personal healthcare monitoring system. Analysis of components in exhaled breath is a practical and non-invasive approach. We focus on the detection of exhaled ammonia (NH3) level which is a critical biomarker associated with hepatitis, kidney failure, and stomach cancer.
We present a novel and industrially scalable inkjet-printed graphene-based sensory system that is integrated onto a miniaturized CMOS MEMS platform. We inkjet-printed nano-composite sensing layer of graphene/ZnO which is synthesized by a cost-effective solution-processing approach. The approach involves liquid phase exfoliation (LPE) of graphite and mixing of ZnO nanoparticles, producing uniformly decorated nanoparticles in a network of graphene flakes.
Our device outperforms conventional metal oxide semiconductor (MOS) sensors via improved gas adsorption ability at materials interface. Moreover, thanks to precisely-controlled thin-film inkjet deposition technologies, we achieve consistent readings among the fabricated devices (<1% variation in response among four devices).
The device is ideal for implementation in smartphones due to its compact size (1mm2) and its ultralow power consumption (5mW). Coupled with rapid temperature modulation of the built-in micro-hotplate, we achieve ultrahigh response of 1600% at 10 ppm of NH3 (compared to N2) at a low operating temperature (150 oC) with fast rise and fall time (30s and 45s, respectively).
The versatile technologies enable multi-analyte sensors to be fabricated reliably and cost-effectively, offering new routes towards the development of multi-disease diagnostics platforms.