Multi-dimensional microwave sensing using graphene waveguides

TL;DR

This paper introduces a multi-dimensional microwave sensor using graphene waveguides integrated with microfluidics, enabling highly sensitive chemical and biological detection through combined microwave and chemical field-effect sensing.

Contribution

It presents a novel graphene-based microwave sensing platform that merges chemical and microwave measurement techniques for enhanced detection capabilities.

Findings

Achieved a detection limit of ~1 attomole per litre for DNA sequences.

Demonstrated a sensitivity of ~3 dB/decade for sub-pM concentrations.

Developed a multidimensional dataset approach for thorough solution analysis.

Abstract

This paper presents an electrolytically gated broadband microwave sensor where atomically-thin graphene layers are integrated into coplanar waveguides and coupled with microfluidic channels. The interaction between a solution under test and the graphene surface causes material and concentration-specific modifications of graphene's DC and AC conductivity. Moreover, wave propagation in the waveguide is modified by the dielectric properties of materials in its close proximity via the fringe field, resulting in a combined sensing mechanism leading to an enhanced S-parameter response compared to metallic microwave sensors. The possibility of further controlling the graphene conductivity via an electrolytic gate enables a new, multi-dimensional approach merging chemical field-effect sensing and microwave measurement methods. By controlling and synchronizing frequency sweeps, electrochemical gating and liquid flow in the microfluidic channel, we generate multidimensional datasets that enable a thorough investigation of the solution under study. As proof of concept, we functionalize the graphene surface in order to identify specific single-stranded DNA sequences dispersed in phosphate buffered saline solution. We achieve a limit of detection of ~1 attomole per litre for a perfect match DNA strand and a sensitivity of ~3 dB/decade for sub-pM concentrations. These results show that our devices represent a new and accurate metrological tool for chemical and biological sensing.