The demand for wearable sensors has grown rapidly in recent years, with increasing attention being given to epidermal chemical sensing. Here, we present the first example of a fully-integrated eyeglasses wireless multiplexed chemical sensing platform capable of real-time monitoring of sweat electrolytes and metabolites. The new concept has been realized by integrating an amperometric lactate biosensor and a potentiometric potassium ion-selective electrode on the two nose bridge pads of the glasses and interfacing them to a wireless electronic backbone placed on the glasses arms. Simultaneous real-time monitoring of sweat lactate and potassium levels with no apparent cross-talk is demonstrated along with wireless signal transduction. The electrochemical sensors were screen printed on a polyethylene terephthalate (PET) stickers and placed on each side of the glasses nose pads in order to monitor sweat metabolites and electrolytes. The electronic backbone on the arms of the glasses frame offers control of the amperometric and potentiometric transducers and enables Bluetooth wireless data transmission to the host device. The new glasses system offers an interchangeable-sensor feature in connection to variety of different nose-bridge amperometric and potentiometric sensor stickers. For example, the lactate bridge-pad sensor was replaced with a glucose one to offer convenient monitoring of sweat glucose. Such fully-integrated wireless “Lab-on-a-Glass” multiplexed biosensor platform can be readily expanded for the simultaneous monitoring of additional sweat electrolytes and metabolites.

Paper-based ion-selective electrodes (ISEs) are simple, flexible, and cost-efficient in comparison to conventional solid-contact ISEs. Yet, paper-based ISEs have poor limits of detection (in the micromolar range) relative to conventional solid-contact ISEs. Here we describe the construction and optimization of ISEs based on commercially available filter paper modified with single-walled carbon nanotubes (SWCNTs), sputtered gold, and conductive polymer poly(3-octylthiophene) to support an ion-selective membrane. The ion-selective membrane presented here is based on the copolymer methyl methacrylate-decyl methacrylate (MMA-DMA). The copolymer MMA-DMA is highly water-repellent and has a low coefficient of diffusion, which makes it particularly suitable for the creation of sensors with high performance in reaching low limits of detection. Three different configurations of the electrodes have been characterized by using contact angle surface analysis, oxygen influence, and testing for the presence of a water layer. Paper-strip ISEs for cadmium, silver, and potassium ions were developed with groundbreaking limits of detection of 1.2, 25.1, and 11.0 nM, respectively. In addition to such low limits of detection, paper-strip ISEs display high selectivity for their ion of interest and high reproducibility.

Preparation of ISEs often requires long and complicated conditioning protocols limiting their application as tools for in field measurements. Herein, we eliminated the need for conditioning by loading the membrane cocktail with primary ion solution. This protocol significantly shortens the preparation time of ISEs yielding functional electrodes with submicromolar detection limits.The scientific research in ion-selective electrodes (ISEs) has gained momentum within the last years due to improvements in the limits of detection and selectivity, becoming now applicable for trace-level measurements by understanding transmembrane ion fluxes. 1 The response of ISEs can be described by the phase boundary potential, E PB , according the following equation:Here a I (aq) and a I (org) are the activities of primary ion (I) of charge z in aqueous and organic phases respectively, while E 0 , R, T, and F are the standard potential, gas constant, temperature and Faraday constant, respectively. When a I (org) is kept constant, the equation 1 reduces to the well-known Nernst equation:In order to render an ion-selective membrane functional, the ionophore and lipophilic ionic sites are required. One of the major roles of ionophore is to make relatively strong complexes with the primary ion, thereby establishing their constant activity in the membrane. 2 For more details see Equations SI1-SI5 in the supporting information. The role of the lipophilic ionic sites is to provide ion-exchange properties. For cation selective membrane, this process could be described by the following equilibrium:where L is a ligand (ionophore) that forms ion-ionophore complex with ion I of stoichiometry n. + − is a lipophilic ion exchanger composed of lipophilic anion R -and its counterion M + . Partitioning of I from aqueous sample into the membrane results in its exchange with M + . Anion − remains in the membrane thereby rendering the membrane permselective while preserving the charge balance. 3 In a typical experimental protocol for the preparation of ion-selective membranes the ion-exchange process is obtained by conditioning (soaking) the membrane in an aqueous solution containing the ion I (traditional protocol). 4 Significant effort in ISEs field has been spent on researching ways to miniaturize 5-9 and optimize/simplify the preparation of ISEs. [10][11][12] Reducing or eliminating the need for the conditioning step prior to the use of the electrodes is an important step for devising a simple, practical protocol for ISEs applications. 12 This would enable nontrained personnel to use ISEs quickly and reliably. In this work we propose a simple alteration of the sensor's conditioning protocol. Instead of placing the ISEs in a solution of primary ions I, solution is added directly into the membrane cocktail prior to its casting. The concentration of that solution is calculated to allow for stoichiometric exchange of I and M. Consequently, ions I are present in the membrane facilitating the formation of ion-ionophore complex according to the ...

Novel optical materials capable of advanced functionality in the infrared will enable optical designs that can offer lightweight or small footprint solutions in both planar and bulk optical systems. UCF's Glass Processing and Characterization Laboratory (GPCL) with our collaborators have been evaluating compositional design and processing protocols for both bulk and film strategies employing multi-component chalcogenide glasses (ChGs). These materials can be processed with broad compositional flexibility that allows tailoring of their transmission window, physical and optical properties, which allows them to be engineered for compatibility with other homogeneous amorphous or crystalline optical components. This paper reviews progress in forming ChG-based GRIN materials from diverse processing methodologies, including solution-derived ChG layers, poled ChGs with gradient compositional and surface reactivity behavior, nanocomposite bulk ChGs and glass ceramics, and meta-lens structures realized through multiphoton lithography (MPL).

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