Using airbrushes to pattern reagents for microarrays and paper-fluidic devices

Flexible Multi-Element Photothermoelectric Detectors Based on Spray-Coated Graphene/Polyethylenimine Composites for Nondestructive Testing

Photothermoelectric (PTE) detectors receive much attention owing to the superiority of self-powered, non-bias input, and friendly ambient environments, facilitating abundant prospective applications in industrial inspection, medical diagnostics, homeland security, and wearable Internet of Things. However, many drawbacks of currently applicable PTE materials, involving unstable material oxidation, an uncontrollable fabrication process, and unscalable manufacturing, hinder the development of industrial productions. Herein, we demonstrate a vertical graphene/polyethylenimine composite PTE detector fabricated with an optimized spray-coating method in compact alignment on various surfaces, achieving a significant photovoltage detectivity and responsivity of 6.05 × 10⁷ cm Hz^1/2 W^-1 and 2.7 V W^-1 response at a 973 K blackbody temperature radiation (2.98 μm peak wavelength). In addition, the long-term stability and resistible concave and convex bending flexibility are presented. Furthermore, a nondestructive testing system is established and verified through high-spatial-resolution and high-penetration illustration. Overall, the spray-coated and flexible PTE graphene/polyethylenimine multi-elements with broadband infrared absorption compatibility and stable energy conversion are promising candidates for future health monitoring and wearable electronics.

Bio-inspired deposition of electrochemically exfoliated graphene layers for electrical resistance heating applications

Electrochemically exfoliated graphene (eeG) layers possess a variety of potential applications, e.g. as susceptor material for contactless induction heating in dynamic electro-magnetic fields, and as flexible and transparent electrode or resistivity heating elements. Spray coating of eeG dispersions was investigated in detail as a simple and fast method to deposit both, thin conducting layers and ring structures on polycarbonate substrates. The spray coating process was examined by systematic variation of dispersion concentration and volume applied to heated substrates. Properties of the obtained layers were characterized by UV-VIS spectroscopy, SEM and Confocal Scanning Microscopy. Electrical conductivity of eeG ring structures was measured using micro-four-point measurements. Modification of eeG with poly(dopamine) and post-thermal treatment yields in the reduction of the oxidized graphene proportion, an increase in electrical conductivity, and mechanical stabilization of the deposited thin layers. The chemical composition of modified eeG layer was analyzed via x-ray photoelectron spectroscopy pointing to the reductive behavior of poly(dopamine). Application oriented experiments demonstrate the direct electric current heating (Joule-Heating) effect of spray-coated eeG layers.

Label-free Paper-based Immunosensor with Graphene Nanocomposites for Electrochemical Detection of Follicle-stimulating Hormone

Follicle-stimulating hormone (FSH) is an important indicator of ovarian reserve function in women in clinical testing. In this work, a label-free paper-based immunosensor was developed for electrochemical rapid detection of FSH. A hydrophilic channel surrounded with hydrophobic barriers was firstly fabricated on the chromatography paper by wax printing technology. Then three electrodes were screen-printed on the circle zones of the channel, in which one carbon electrode further modified by reduced graphene-oxide /thionine /gold nanoparticles nanocomposites and FSH monoclonal antibody was used as the working electrode to provide sensitivity of the immunosensor. The detection of FSH is based on the decreased electrochemical current of Thi produced from the specific binding of the FSH and anti-FSH, and the decrease of the current is proportional to the concentration of the FSH. The experimental results exhibited that the immunosensor could be used to detect the standard FSH in range of 1-100 mIU/mL with the detection limit of 1 mIU/mL. And the proposed immunosensor had been successfully applied to detect FSH in serum samples.