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The fabrication and performance of a wearable paper‐based chemiresistor for monitoring perspiration dynamics (sweat rate and sweat loss) are detailed. A novel approach is introduced to measure the amount of aqueous solution in the order of microliters delivered to the sensor by monitoring a linear change in resistance along a conducting paper. The wearable sensor is based on a single‐walled carbon nanotubes and surfactant (sodium dodecylbenzenesulfonate) nanocomposite integrated within cellulose fibers of a conventional filter paper. The analytical performance and the sensing mechanism are presented. Monitoring sweat loss in the human body while exercising is demonstrated using the integration of a wireless reader and a user‐friendly interface. By addressing the barriers of cost, simplicity, and the truly in situ demanding measurements, this unique wearable sensor is expected to serve in the future in many different applications involving the on‐body detection of biofluids, such as a monitoring tool of dehydration levels for athletes as well as a tool for enhancing the sport performance by providing an accurate recovery of the hydration status in daily exercises.

Objective. To determine the frequency and distribution of ABO and Rh (D) antigens and, additionally, investigate gene diversity and the structure of Mexican populations.Materials and Methods. Blood groups were tested in 271,164 subjects from 2014 to 2016. The ABO blood group was determined by agglutination using the antibodies anti-A, Anti-B, and Anti-D for the Rh factor, respectively.Results. The overall distribution of ABO and Rh (D) groups in the population studied was as follows: O: 61.82%; A: 27.44%; B: 8.93%; and AB: 1.81%. For the Rh group, 95.58% of people were Rh (D), and 4.42% were Rh (d). Different distributions of blood groups across regions were found; additionally, genetic analysis revealed that theIOandIDallele showed an increasing trend from the north to the center, while theIAandIdallele tended to increase from the center to the north. Also, we found more gene diversity in bothlociin the north compared with the center, suggesting population structure in Mexico.Conclusion. This work could help health institutions to identify where they can obtain blood products necessary for medical interventions. Moreover, this piece of information contributes to the knowledge of the genetic structure of the Mexican populations which could have significant implications in different fields of biomedicine.

The potentiometric response to hydrogen peroxide of a platinum electrode coated with a layer of Nafion is presented. The results show that the Nafion membrane acts as an effective permselective barrier, thus significantly reducing the response to some redox active species, such as ascorbate. Even more interesting, these coated electrodes show a significantly enhanced sensitivity to hydrogen peroxide (H2O2) when the measurements are performed in solutions of high ionic strength. The influence of pH, ionic strength and supporting electrolyte on this enhancement are presented. Under optimized conditions these coated electrodes show a linear dependence with the logarithm of the concentration of H2O2, with sensitivities of -125.1 +/- 5.9mVdecade(-1) (several times higher than the bare electrodes) and a linear range that spans from 10(-5) M to 10(-3) M of H2O2. Preliminary studies suggest that the coupling between the redox potential on the Pt electrode and the Donnan potential of the membrane plays a role on this enhancement. Considering this improved sensitivity, selectivity, stability and linear ranges, this system shows promise as a future platform to build enzyme-based potentiometric biosensors.

The use of commercial carbon fibres (CCF) to build wearable potentiometric sensors for the real-time monitoring of sodium levels in sweat during exercise is presented. CCF are an attractive substrate for building wearable electrochemical sensors because of their good electrical conductivity, chemical inertness, flexibility and mechanical resilience. In the first part of this work, the analytical performance of these novel potentiometric ion-selective electrodes made with CCFs is presented. Then, through the incorporation of a solid-contact reference electrode, the development of a complete miniaturized potentiometric cell with a Nernstian response (59.2 +/- 0.6mV/log [Na+], N=4) is obtained. Finally, the cell is integrated into a wearable patch and attached onto the skin of an athlete. The analytical characterization of the wearable patch shows a near-Nernstian response (55.9 +/- 0.8mV/log [Na+], N=3) for sodium levels from 10(-3)M to 10(-1)M in artificial sweat, well within the physiological range of interest. The device shows low noise levels and very good stability (-0.4 +/- 0.3mVh(-1)). To improve the usability of the sensor in real scenarios, a calibration-free approach is also explored. This platform opens new and attractive avenues for the generation of meaningful personalized physiological information that could be applied - among many other fields - in sports, nutrition and healthcare.

Balloon-embedded stretchable sensors, undergoing a simultaneous equal-multiaxial stretching along global bending motion, have been characterized and tested towards environmental and security monitoring missions. Stress-enduring inks are printed on the curvilinear surface of conventional rubber balloons and their resilience to extreme mechanical deformations, associated with repeated inflation and deflation cycles, is investigated. Unlike early studies of mechanical deformed electrochemical devices-performed with linear stretching or bending-the present balloon-embedded sensors undergo simultaneous multidimensional strains without any alteration of its electrochemical properties. Careful attention is given to the elastomeric, electrical, and electrochemical properties of the new expandable composite inks for addressing the extreme demands of the inflated spherical dynamic balloon substrate. The influence of the balloon inflation and corresponding multiaxial mechanical stress upon the electrochemical behavior is modeled analytically. The electrochemical detection of relevant military and homemade explosives in liquid and vapor phases is used to demonstrate the functionality and potential of the new balloon sensor system to diverse environmental and defense missions. Negligible changes in the response to explosive compounds are observed following multiple repeated inflation and deflation cycles, involving over 400% increase of the balloon area.

A simple and generalized approach to build electrochemical sensors for wearable devices is presented. Commercial cotton yarns are first turned into electrical conductors through a simple dyeing process using a carbon nanotube ink. These conductive yarns are then partially coated with a suitable polymeric membrane to build ion-selective electrodes. Potentiometric measurements using these yarn-potentiometric sensors are demonstrated. Examples of yarns that can sense pH, K+ and NH4+ are presented. In all cases, these sensing yarns show limits of detection and linear ranges that are similar to those obtained with lab-made solid-state ion-selective electrodes. Through the immobilization of these sensors in a band-aid, it is shown that this approach could be easily implemented in a wearable device. Factors affecting the performance of the sensors and future potential applications are discussed.