Graphene Field Effect Biosensor for Concurrent and Specific Detection of SARS-CoV-2 and Influenza.

The SARS-CoV-2 pandemic has highlighted the need for devices capable of carrying out rapid differential detection of viruses that may manifest similar physiological symptoms yet demand tailored treatment plans. Seasonal influenza may be exacerbated by COVID-19 infections, increasing the burden on healthcare systems. In this work, we demonstrate a technology based on liquid-gated graphene field-effect transistors (GFETs), for rapid and ultraprecise sensing and differentiation of influenza and SARS-CoV-2 surface protein. Most distinctively, the device consists of 4 onboard GFETs arranged in a quadruple architecture, where each quarter is functionalized individually (with either antibodies or chemically passivated control) but measured jointly. The sensor platform was tested against a range of concentrations of viral surface proteins from both viruses with the lowest tested and detected concentration at ∼50 ag/mL, or 88 zM for COVID-19 and 227 zM for Flu, which is 5-fold lower than the values reported previously on a similar platform. Unlike the classic real-time polymerase chain reaction test, which has a turnaround time of a few hours, the graphene technology presents an ultrafast response time of ∼10 s even in complex and clinically relevant media such as saliva. Thus, we have developed a multianalyte, highly sensitive, and fault-tolerant technology for rapid diagnostic of contemporary, emerging, and future pandemics.

Continuous cuffless monitoring of arterial blood pressure via graphene bioimpedance tattoos.

Continuous monitoring of arterial blood pressure (BP) in non-clinical (ambulatory) settings is essential for understanding numerous health conditions, including cardiovascular diseases. Besides their importance in medical diagnosis, ambulatory BP monitoring platforms can advance disease correlation with individual behaviour, daily habits and lifestyle, potentially enabling analysis of root causes, prognosis and disease prevention. Although conventional ambulatory BP devices exist, they are uncomfortable, bulky and intrusive. Here we introduce a wearable continuous BP monitoring platform that is based on electrical bioimpedance and leverages atomically thin, self-adhesive, lightweight and unobtrusive graphene electronic tattoos as human bioelectronic interfaces. The graphene electronic tattoos are used to monitor arterial BP for >300 min, a period tenfold longer than reported in previous studies. The BP is recorded continuously and non-invasively, with an accuracy of 0.2 ± 4.5 mm Hg for diastolic pressures and 0.2 ± 5.8 mm Hg for systolic pressures, a performance equivalent to Grade A classification.

Laser-Induced Direct Patterning of Free-standing Ti3C2-MXene Films for Skin Conformal Tattoo Sensors.

The discovery of stable two-dimensional (2D) materials has effectuated a rapid evolution of skin conformal sensors for health monitoring via epidermal electronics. Among the newly discovered 2D materials, MXene stands out as a solution-processable 2D material allowing easy fabrication of highly conductive thin films with the potential to realize flexible skin conformal sensors. Here, we present a successful demonstration of a Ti3C2-MXene resistor as an extremely sensitive strain sensor in the form an ultrathin skin mountable temporary tattoo. The skin conformability and form factor afforded by the sensor promises inconspicuous and continuous monitoring of vital health parameters of an individual, like the pulse rate, respiration rate, and surface electromyography. The sensor serves as a single conduit for sensing the respiration rate and pulse, dispensing with the need of mounting multiple sensors. Its remarkably high sensitivity with a gauge factor of ∼7400 has been ascribed to development of nanocracks and their propagation through the film upon application of strain. The fast response and highly repeatable sensor follows easy fabrication steps and can be patterned into any shape and size using a laser.

Electric Spark Induced Instantaneous and Selective Reduction of Graphene Oxide on Textile for Wearable Electronics.

Reduced graphene oxide (rGO) attracts great popularity as an alternative to pristine graphene because of the facile synthesis process of its precursor, graphene oxide (GO). Electrical conduction of GO is tunable, subject to the extent of reduction of oxygen functional groups in it. This work for the first time demonstrates rapid reduction of GO using spark at ambient conditions. A stream of spark generated by applying high electric potential across two electrodes, when passed through a film of GO deposited on a porous substrate, reduces it into rGO. Upon sparking, the electrical resistance of the GO film drops down by an order of six within a second, making the reduction process instantaneous. X-ray photoelectron spectroscopy and Raman spectra of spark-reduced graphene oxide (SrGO) films revealed a high C/O ratio with an increase in the domain of sp2-hybridized carbon. The electromechanical properties of SrGO were practically examined by testing it as a flex sensor by incorporating its films with commercially available gloves. It showed high sensitivity for bending and good repeatability while offering an easy route for textile integration, making an impactful statement about the potential of sparking as a cost-effective method to reduce GO on a large scale.