Sensitive and specific DNA biomarker detection is critical for accurately diagnosing a broad range of clinical conditions. However, the incorporation of such biosensing structures in integrated microfluidic devices is often complicated by the need for an additional labelling step to be implemented on the device. In this review we focused on presenting recent advances in label-free DNA biosensor technology, with a particular focus on microfluidic integrated devices. The key biosensing approaches miniaturized in flow-cell structures were presented, followed by more sophisticated microfluidic devices and higher integration examples in the literature. The option of full DNA sequencing on microfluidic chips via nanopore technology was highlighted, along with current developments in the commercialization of microfluidic, label-free DNA detection devices.

The concept of micro-total analysis systems (µTAS) introduced in the early 1990s revolutionized the development of lab-on-a-chip (LoC) technologies by miniaturizing and automating complex laboratory processes. Despite their potential in diagnostics, drug development, and environmental monitoring, the widespread adoption of LoC systems has been hindered by challenges in scalability, integration, and cost-effective mass production. Traditional substrates like silicon, glass, and polymers struggle to meet the multifunctional requirements of practical applications. Lab-on-Printed Circuit Board (Lab-on-PCB) technology has emerged as a transformative solution, leveraging the cost-efficiency, scalability, and precision of PCB fabrication techniques. This platform facilitates the seamless integration of microfluidics, sensors, and actuators within a single device, enabling complex, multifunctional systems suitable for real-world deployment. Recent advancements have demonstrated Lab-on-PCB’s versatility across biomedical applications, such as point-of-care diagnostics, electrochemical biosensing, and molecular detection, as well as drug development and environmental monitoring. This review examines the evolution of Lab-on-PCB technology over the past eight years, focusing on its applications and impact within the research community. By analyzing recent progress in PCB-based microfluidics and biosensing, this work highlights how Lab-on-PCB systems address key technical barriers, paving the way for scalable and practical lab-on-chip solutions. The growing academic and industrial interest in Lab-on-PCB is underscored by a notable increase in publications and patents, signaling its potential for commercialization and broader adoption.

The recent COVID-19 outbreak highlighted the need for lab-on-chip diagnostic technology fit for real-life deployment in the field. Existing bottlenecks in multistep analytical microsystem integration and upscalable, standardized fabrication techniques delayed the large-scale deployment of lab-on-chip solutions during the outbreak, throughout a global diagnostic test shortage. This study presents a technology that has the potential to address these issues by redeploying and repurposing the ubiquitous printed circuit board (PCB) technology and manufacturing infrastructure. We demonstrate the first commercially manufactured, miniaturised lab-on-PCB device for loop-mediated isothermal amplification (LAMP) genetic detection of SARS-CoV-2. The system incorporates a mass-manufactured, continuous-flow PCB chip with ultra-low cost fluorescent detection circuitry, rendering it the only continuous-flow μLAMP platform with off-the-shelf optical detection components. Ultrafast, SARS-CoV-2 RNA amplification in wastewater samples was demonstrated within 2 min analysis, at concentrations as low as 17 gc μL⁻¹. We further demonstrate our device operation by detecting SARS-CoV-2 in 20 human nasopharyngeal swab samples, without the need for any RNA extraction or purification. This renders the presented miniaturised nucleic-acid amplification-based diagnostic test the fastest reported SARS-CoV-2 genetic detection platform, in a practical implementation suitable for deployment in the field. This technology can be readily extended to the detection of alternative pathogens or genetic targets for a very broad range of applications and matrices. LoCKAmp lab-on-PCB chips are currently mass-manufactured in a commercial, ISO-compliant PCB factory, at a small-scale production cost of £2.50 per chip. Thus, with this work, we demonstrate a high technology-readiness-level lab-on-chip-based genetic detection system, successfully benchmarked against standard analytical techniques both for wastewater and nasopharyngeal swab SARS-CoV-2 detection.

Graphene oxide (GO) is a promising material for H2O vapour sensing. However, H2O sensing mechanisms are still under investigation especially in the case of thermally reduced GO. To this purpose, planar devices were fabricated by spin-coating graphene oxide on glass substrates. Ultra high response to H2O was recorded but poor repeatability and stability over time were also noted. Three different degrees of thermal reduction were applied to improve material stability. An inverse change of resistance was observed for reduced graphene oxide compared to pure graphene oxide upon interaction with H2O. The sensing mechanisms that govern GO and reduced GO behaviour were studied based on DC measurements. In the case of GO, strong ionic conductivity was proposed whereas in the case of reduced GO mixed electronic/ionic with the leading mechanism affected by H2O percentage in air, degree of material reduction and sensor working temperature. Finally, it was found that by promoting one sensing mechanism over the other, improved operating humidity range of the sensor can be achieved.

We demonstrate permanent water trapping in reduced graphene oxide after high relative humidity exposure. For this purpose, we grew graphene oxide films via spin-coating on glass substrates followed by thermal reduction. The electrical resistance of the planar device was then measured. We observed that resistance is significantly increased after water vapor exposure and remains stable even after 250 days in ambient conditions. Various techniques were applied to desorb the water and decrease (recover) the material's resistance, but it was achieved only with low temperature thermal annealing (180 °C) under forming gas (H₂/N₂ mixture). The permanent effect of water absorption was also detected by x-ray photoelectron spectroscopy.