The Communication describes a textile-based wearable multi-ion potentiometric sensor array. The printed flexible sensors operate favorably under extreme mechanical strains (that reflect daily activity) while offering attractive real-time non-invasive monitoring of electrolytes such as sodium and potassium.

Herein, the reproducibility and a double validation of on-body measurements provided by new wearable potentiometric ion sensors (WPISs) is presented. Sweat collected during sport practice was first analyzed using the developed device, the pH-meter, and ion chromatography (IC) prior to on-body measurements (off-site validation). Subsequently, the accuracy of on-body measurements accomplished by the WPISs was evaluated by comparison with pH-meter readings and IC after collecting sweat (every 10–12.5 min) during sport practice. The developed device contains sensors for pH, Cl–, K+, and Na+ that are embedded in a flexible sampling cell for sweat analysis. The electrode array was fabricated employing MWCNTs (as an ion-to-electron transducer) and stretchable materials that have been exhaustively characterized in terms of analytical performance, presenting Nernstian slopes within the expected physiological range of each ion analyte (Cl–, 10–100 mM; K+, 10–10 mM; and Na+, 10–100 mM and pH, 4.5–7.5), drift suitable for midterm exercise practice (0.3 ± 0.2 mV h–1), fast response time, adequate selectivity for sweat measurements, and excellent reversibility. Besides that, the designed sampling cell avoids any sweat contamination and evaporation issues while supplying a passive sweat flow encompassing specifically the individual’s perspiration. The interpretation of ion concentration profiles may permit the identification of personal dynamic patterns in sweat composition while practicing sport.

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We present the most complete study to date comprising in vitro cytotoxicity tests of ion-selective membranes (ISMs) in terms of cell viability, proliferation, and adhesion assays with human dermal fibroblasts. ISMs were prepared with different types of plasticizers and ionophores to be tested in combination with assays that focus on the medium-term and long-term leaching of compounds. Furthermore, the ISMs were prepared in different configurations considering (i) innerfilling solution-type electrodes, (ii) all-solid-state electrodes based on a conventional drop-cast of the membrane, (iii) peeling after the preparation of a wearable sensor, and (iv) detachment from a microneedle-based sensor, thus covering a wide range of membrane shapes. One of the aims of this study, other than the demonstration of the biocompatibility of various ISMs and materials tested herein, is to create an awareness in the scientific community surrounding the need to perform biocompatibility assays during the very first steps of any sensor development with an intended biomedical application. This will foster meeting the requirements for subsequent on-body application of the sensor and avoiding further problems during massive validations toward the final in vivo use and commercialization of such devices.

Balloon-embedded stretchable sensors, undergoing a simultaneous equalmultiaxial 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 infl ation and defl ation 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 infl ated spherical dynamic balloon substrate. The infl uence of the balloon infl ation 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 infl ation and defl ation cycles, involving over 400% increase of the balloon area.