The use of fully printed electrochemical devices has gained more attention for the monitoring of clinical, food, and environmental analytes due to their low cost, great reproducibility, and versatility characteristics, serving as an important technology for commercial application. Therefore, a paper-based inkjet-printed electrochemical system is proposed as a cost-effective analytical detection tool for paraquat. Chromatographic paper was used as the printing substrate due its sustainable and disposable characteristics, and an inkjet-printing system deposited the conductive silver ink with no further modification on the paper surface, providing a three-electrode system. The printed electrodes were characterized with scanning electron microscopy, cyclic voltammetry, and chronopotentiometry. The proposed sensor exhibited a large surface area, providing a powerful tool for paraquat detection due to its higher analytical signal. For the detection of paraquat, square-wave voltammetry was used, and the results showed a linear response range of 3.0–100 μM and a detection limit of 0.80 µM, along with the high repeatability and disposability of the sensor. The prepared sensors were also sufficiently selective against interference, and high accuracy (recovery range = 96.7–113%) was obtained when applied to samples (water, human serum, and orange juice), showing the promising applicability of fully printed electrodes for electrochemical monitoring.

Over the past few years, the emergence of electrochemical wearable sensors has attracted considerable attention because of their promising application in point-of-care testing due to some features such as high sensitivity, simplicity, miniaturization, and low fabrication cost. Recent developments in new fabrication approaches and innovative substrates have resulted in sensors able to real-time and on-body measurements. Wearable electrochemical sensors have also been combined with paperbased substrates and directly used on human skin for different applications for non-invasive analyses. Furthermore, wearable electrochemical sensors enable monitoring analytes in different biofluids without complex procedures, such as pre-treatment or sample manipulation. The coupling of IoT to various wearable sensors has also attracted attention due to real-time data collection and handling in remote and resource-limited conditions. This mini-review presents the significant advances in developing wearable electrochemical devices, such as sampling, data collection, connection protocols, and power sources, and discusses some critical challenges for higher performance in this field. We also present an overview of the application of paper as an intelligent substrate for electrochemical wearable sensors and discuss their advantages and drawbacks. Lastly, conclude by highlighting the future advances in wearable sensors and diagnostics by coupling real-time and on-body measurements to multiplexed detection of different biomarkers simultaneously, reducing the cost and time of classical analysis to provide fast and complete overall physiological conditions to the wearer.

The demand for wearable sensors has been grown rapidly over the past few years, mainly those related to monitor health, fitness and their surroundings. Consequently, wearable chemical sensing has become a crucial appliance area for wireless sensors and has proved to be a very challenging and multidisciplinary area. The great advantage of coupling wireless communication to different types of wearable sensors is the enhancement of the sensor’s scope for remote and resource-limited settings with the possibility of obtaining real-time data acquisition and application in different areas like homeland defense, home-based healthcare, and food logistics. Being the electrochemical sensors considered attractive and promising to use in the wireless chemical sensor field, due to its features such as simple structure, the possibility of miniaturization, comfort, simplicity of operation, high sensitivity, fast response, relatively low energy consumption and low manufacturing cost. Furthermore, wearable electrochemical sensors enable obtaining insights into individuals' health status through the noninvasive monitoring of clinically relevant biomarkers in different biofluids without complex sampling, manipulation and treatment steps. In this review, we present the main advances in technologies used in the development of fully integrated wireless wearable electrochemical devices, such as communication protocols, data collection and privacy concerns and power sources. We also discuss in a critical way the main challenges, trends, strategies and new technologies that will drive this research line in the future. Lastly, we highlight the progress in the last few years in healthcare, sports, security and defense, and forensic applications.

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