Our health in our hands: Surface decorated metasurfaces for sensing exhaled breath markers & solid-state nanopores towards complex sample sensing.

The development of highly sensitive, portable and selective sensing technologies capable of detecting disease biomarkers is vital for early detection and monitoring of adverse health conditions like diabetes and multiple sclerosis. ‘Our Health in Our Hands’ (OHIOH) is a research initiative by the Australian National University to develop innovative technologies to this end, and in turn we explore several platforms i.e.: optical metasurfaces, chemiresistive devices, electrochemical sensors and solid-state nanopore sensors. Here we discuss our work on dielectric metasurfaces for label-free sensing. Metasurfaces are nanostructured 2D surfaces that possess intriguing optical properties. With low losses, high quality-factors and electric field extended beyond the surface following light interaction, these metasurfaces are highly sensitive to the refractive index (RI) change induced by placing target molecules on the metasurface. However, metasurfaces lack the selectivity towards a target molecule, that mitigates its real-world applications in complex sample testing. Additionally, they are not sensitive enough for gas sensing due to the ultra-small RI change caused by gas molecule adsorption on bare metasurfaces. To overcome these challenges, we use surface decorated metasurfaces—by organic functional layers and metal textures—for highly sensitive and selective bio and gas sensing to monitor biological samples and volatile organic compounds (VOCs) in breath. In gas sensing, our decorated metasurfaces operate at ambient conditions vs most gas sensors and can be regenerated when VOC is removed making the sensor reusable and pragmatic. We demonstrated the textured metasurfaces elevating the sensor response significantly and sensing acetone down to 0.1% concentration. Moreover, we explore solid-state nanopores to characterize proteins at single-molecular level with bandwidths up to 10 MHz to uncover unattenuated and ultra-fast translocation events towards developing technologies to monitor adverse health conditions.