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We demonstrate a novel system for the detection and discrimination of varying levels of exposure to gunshot residue from subjects in various control scenarios. Our aim is to address the key challenge of minimizing the false positive identification of individuals suspected of discharging a firearm. The chemometric treatment of voltammetric data from different controls using Canonical Variate Analysis (CVA) provides several distinct clusters for each scenario examined. Multiple samples were taken from subjects in controlled tests such as secondary contact with gunshot residue (GSR), loading a firearm, and postdischarge of a firearm. These controls were examined at both bare carbon and gold-modified screen-printed electrodes using different sampling methods: the ‘swipe’ method with integrated sampling and electroanalysis and a more traditional acid-assisted q-tip swabbing method. The electroanalytical fingerprint of each sample was examined using square-wave voltammetry; the resulting data were preprocessed with Fast Fourier Transform (FFT), followed by CVA treatment. High levels of discrimination were thus achieved in each case over 3 classes of samples (reflecting different levels of involvement), achieving maximum accuracy, sensitivity, and specificity values of 100% employing the leave-one-out validation method. Further validation with the ‘jack-knife’ technique was performed, and the resulting values were in good agreement with the former method. Additionally, samples from subjects in daily contact with relevant metallic constituents were analyzed to assess possible false positives. This system may serve as a potential method for a portable, field-deployable system aimed at rapidly identifying a subject who has loaded or discharged a firearm to verify involvement in a crime, hence providing law enforcement personnel with an invaluable forensic tool in the field Refereed/Peer-reviewed

Objective: Current continuous glucose monitors (CGM) measure glucose in the subcutaneous interstitial fluid (ISF). Previous ex vivo research with hypodermic needles has shown that glucose in the dermal ISF is highly correlated to venous glucose with little or no lag time. However, this methodology is not viable for continuous measurement. In this study, we have developed and tested a wearable microneedle array sensor for continuous in situ measurement of glucose in the dermal ISF. A dermal CGM could be applied without an introducer needle and without pain during application. Methods: In this study the microneedle array sensor was tested against venous glucose measured every 15 minutes from a YSI analyzer in 8-hour sessions over 2 days (Phase One) and 5-7 days (Phase Two). Results: Five participants without diabetes and 10 participants with diabetes were recruited for phase One and 10 participants with diabetes were recruited for phase Two. A high degree of linear correlation (R2 ≥ 0 .90) between the microneedle array measured dermal ISF glucose and venous glucose was observed. The figure shows the linear correlation (A) and temporal profile (B) for one microneedle array sensor over 8 hours. Conclusions: A wearable microneedle array measuring dermal ISF glucose can accurately track glucose values. The study demonstrated early human feasibility of a CGM based on microneedle sensing of dermal ISF. Disclosure P.P. Samant: Employee; Self; Biolinq. M.P. Christiansen: Research Support; Self; Abbott, Ascensia Diabetes Care, Biolinq, Dexcom, Inc., Eli Lilly and Company, Lexicon Pharmaceuticals, Inc., Medtronic, Merck & Co., Inc., Novo Nordisk A/S, Sanofi-Aventis, Senseonics, ViroMed Laboratories, Xeris Pharmaceuticals, Inc. S. Sattayasamitsathit: None. A. Campbell: None. T.A. Peyser: Consultant; Self; Insulet Corporation. Employee; Self; Biolinq. J.R. Windmiller: Employee; Self; Biolinq. J.R. Tangney: Board Member; Self; Biolinq. R. Lal: Consultant; Self; Abbott, Biolinq. N.C. Bhavaraju: Employee; Self; Biolinq.

The present work describes an attractive skin-worn microneedle sensing device for the minimally invasive electrochemical monitoring of subcutaneous alcohol. The device consists of an assembly of pyramidal microneedle structures integrated with Pt and Ag wires, each with a microcavity opening. The microneedle aperture was modified by electropolymerizing o-phenylene diamine onto the Pt wire microtransducer, followed by the immobilization of alcohol oxidase (AOx) in an intermediate chitosan layer, along with an outer Nafion layer. The resulting microneedle-based enzyme electrode displays an interference-free ethanol detection in artificial interstitial fluid without compromising its sensitivity, stability and response time. The skin penetration ability and the efficaciousness of the biosensor performance towards subcutaneous alcohol monitoring was substantiated by the ex vivo mice skin model analysis. Our results reveal that the new microneedle sensor holds considerable promise for continuous non-invasive alcohol monitoring in real-life situations.

A microneedle-based self-powered biofuel-cell glucose sensor is described. The biofuel cell sensor makes use of the integration of modified carbon pastes into hollow microneedle devices. The system displays defined dependence of the power density vs glucose concentration in artificial interstitialfluid. An excellent selectivity against common electroactive interferences and long-term stability are obtained. The attractive performance of the device indicates considerable promise for subdermal glucose monitoring. Keywords: Microneedle array, Glucose, Self-powered sensor, Biofuel cell

The present work describes the first example of real-time noninvasive lactate sensing in human perspiration during exercise events using a flexible printed temporary-transfer tattoo electrochemical biosensor that conforms to the wearer's skin. The new skin-worn enzymatic biosensor exhibits chemical selectivity toward lactate with linearity up to 20 mM and demonstrates resiliency against continuous mechanical deformation expected from epidermal wear. The device was applied successfully to human subjects for real-time continuous monitoring of sweat lactate dynamics during prolonged cycling exercise. The resulting temporal lactate profiles reflect changes in the production of sweat lactate upon varying the exercise intensity. Such skin-worn metabolite biosensors could lead to useful insights into physical performance and overall physiological status, hence offering considerable promise for diverse sport, military, and biomedical applications.

This article reviews recent advances and developments in the field of wearable sensors with emphasis on a subclass of these devices that are able to perform highly-sensitive electrochemical analysis. Recent insights into novel fabrication methodologies and electrochemical techniques have resulted in the demonstration of chemical sensors able to augment conventional physical measurements (i.e. heart rate, EEG, ECG, etc.), thereby providing added dimensions of rich, analytical information to the wearer in a timely manner. Wearable electrochemical sensors have been integrated onto both textile materials and directly on the epidermis for various monitoring applications owing to their unique ability to process chemical analytes in a non-invasive and non-obtrusive fashion. In this manner, multi-analyte detection can easily be performed, in real time, in order to ascertain the overall physiological health of the wearer or to identify potential offenders in their environment. Of profound importance is the development of an understanding of the impact of mechanical strain on textile- and epidermal (tattoo)-based sensors and their failure mechanisms as well as the compatibility of the substrate employed in the fabrication process. We conclude this review with a retrospective outlook of the field and identify potential implications of this new sensing paradigm in the healthcare, fitness, security, and environmental monitoring domains. With continued innovation and detailed attention to core challenges, it is expected that wearable electrochemical sensors will play a pivotal role in the emergent body sensor networks arena.

This article describes a rapid and reliable electrochemical/enzymatic method of verifying the presence of nitroaromatic explosives. The new technique leverages both conventional voltammetric analysis and biocatalytic conversion of TNT. The simultaneous use of independent measurement schemes, based on two distinct processes, dramatically increases the information content and offers substantially improved reliability while minimizing the occurrence of false alarms. This has been accomplished by coupling direct voltammetric analysis with the biocatalytic conversion of the TNT substrate via nitroreductase (NR), which reduces a nitro group of TNT using NADH as an electron donor. This chemical reduction (30 s timescale) can then be observed using square-wave voltammetry by examination of the reductive and oxidative features. This novel protocol was found to be selective for TNT, not only when compared to DNT and NT, but also to other explosive species such as RDX and PETN. This unique dual-mode detection strategy for measuring TNT at a single device holds considerable promise for improving the probability of explosive detection and hence for diverse security screening applications.

Bio-logic-al: an autonomous, integrated "sense-act-treat" system that is based on an enzymatic biofuel cell has been developed. The system couples a biocomputing logic-detection method with a drug-release system to provide a logic-activated therapeutic intervention in response to a simulated abnormal physiological state, without the need for an external power source, control electronics, or microelectromechanical actuators.

We report on the development of a microneedle-based multiplexed drug delivery actuator that enables the controlled delivery of multiple therapeutic agents. Two individually addressable channels on a single microneedle array, each paired with its own reservoir and conducting polymer nanoactuator, are used to deliver various permutations of two unique chemical species. Upon application of suitable redox potentials to the selected actuator, the conducting polymer is able to undergo reversible volume changes, thereby serving to release a model chemical agent in a controlled fashion through the corresponding microneedle channels. Time-lapse videos offer direct visualization and characterization of the membrane switching capability and, along with calibration investigations, confirm the ability of the device to alternate the delivery of multiple reagents from individual microneedles of the array with higher precision and temporal resolution than conventional drug delivery actuators. Analytical modeling offers prediction of the volumetric flow rate through a single microneedle and accordingly can be used to assist in the design of subsequent microneedle arrays. The robust solid-state design and lack of mechanical components circumvent reliability issues that challenge fragile conventional microelectromechanical drug delivery devices. This proof-of-concept study demonstrates the potential of the drug delivery actuator system to aid in the rapid administration of multiple therapeutic agents and indicates the potential to counteract diverse biomedical conditions.

We report on the development of a rapid enzyme logic gate-based electrochemical assay for the assessment of traumatic brain injury (TBI). The concept harnesses a biocatalytic cascade that emulates the functionality of a Boolean NAND gate in order to process relevant physiological parameters in the biochemical domain. The enzymatic backbone ensures that a high-fidelity diagnosis of traumatic brain injury can be tendered in a rapid fashion when the concentrations of key serum-based biomarkers reach pathological levels. The excitatory neurotransmitter glutamate and the enzyme lactate dehydrogenase were used here as clinically-relevant input TBI biomarkers, in connection to the low-potential detection of the NADH product in the presence of methylene green at a glassy carbon electrode. A systematic optimization of the gate and the entire protocol has resulted in the effective discrimination between the physiological and pathological logic levels. Owing to its robust design, the enzyme-based logic gate mitigates potential interferences from both physiological and electroactive sources and is able to perform direct measurements in human serum samples. Granted further detailed clinical validation, this proof-of-concept study demonstrates the potential of the electrochemical assay to aid in the rapid and decentralized diagnosis of TBI.

This article describes the design of a new and attractive minimally-invasive bicomponent microneedle sensing device for the electrochemical monitoring of the excitatory neurotransmitter glutamate and glucose. The new device architecture relies on the close integration of solid and hollow microneedles into a single biosensor array device containing multiple microcavities. Such microcavities facilitate the electropolymeric entrapment of the recognition enzyme within each microrecess. The resulting microneedle biosensor array can be employed as a minimally-invasive on-body transdermal patch, obviating the extraction/sampling of the biological fluid, thereby simplifying device requirements. The new concept is demonstrated for the electropolymeric entrapment of glutamate oxidase and glucose oxidase within a poly(o-phenylenediamine) (PPD) thin film. The PPD-based enzyme entrapment methodology enables the effective rejection of coexisting electroactive interferents without compromising the sensitivity or response time of the device. The resulting microneedle-based glutamate and glucose biosensors thus exhibit high selectivity, sensitivity, speed, and stability in both buffer and undiluted human serum. High-fidelity glutamate measurements down to the 10 µM level are obtained in serum. The attractive recess design also serves to protect the enzyme layer upon insertion into the skin. This simple, yet robust microneedle design is well-suited for diverse biosensing applications in which real-time metabolite monitoring is a core requirement.

In this work we describe the development of a novel microelectronic backbone configured specifically for the control of biocomputing systems applied to diagnostic merits. The operation of the sensor system is validated towards the rapid assessment of pathological conditions arising from soft tissue injury (STI) and abdominal trauma (ABT) using NAND and AND Boolean enzyme logic gates, respectively. The miniaturized 19 × 19 mm device employs a custom-designed three-electrode potentiostat coupled with an integrator, voltage amplifier, comparator, and digital logic and is easily interfaced with a screen-printed electrode contingent. By implementing an adjustable threshold comparator, a precise decision threshold could be established corresponding to pathological levels of the target biomarkers. As a result, a rapid amperometric analysis tendered the diagnosis in a straightforward ‘YES’/‘NO’ digital format via the illumination of a light emitting diode. Using low quiescent current voltage regulators, the device is able to achieve microwatt power operation and can be sustained by a single 3 V coin-cell battery for over 45 h under continuous use. The low-power, low-cost, and miniaturized device meets the requirements of field-deployable logic gate amperometric sensors. Such a reconfigurable micro-/bioelectronic logic-based multi-parameter sensing system shows considerable potential for the assessment of key analytes in a multitude of relevant clinical, security, and environmental applications where go/no-go readout, rapid measurement, device miniaturization, and extended longevity on battery power are key requirements.

This study examines the influence of textile substrates upon the behavior of wearable screen-printed electrodes and demonstrates the attractive sensing properties of these sensors towards the detection of nitroaromatic explosives. Compared to electrodes printed on common cotton or polyester substrates, GORE-TEX-based electrochemical sensors display reproducible background cyclic voltammograms, reflecting the excellent water-repellant properties of the GORE-TEX fabric. The wetting properties of different printed textile electrodes are elucidated using contact angle measurements. The influence of laundry washing and mechanical stress is explored. The GORE-TEX-based printed electrodes exhibit favorable detection of 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) explosives, including rapid detection of DNT vapor.

The development of a novel enzyme logic sensing concept for the detection of soft tissue injury (STI) is reported. The new biocatalytic scheme employs creatine kinase (CK) and lactate dehydrogenase (LDH) as enzyme biomarker inputs to a biochemical cascade that mimics the operational functionality of a NAND Boolean logic gate. Under the optimal conditions, physiological and pathological levels of CK and LDH are detected optically and electrochemically by monitoring the level of reduced nicotinamide adenine dinucleotide (NADH) as an output of the logic gate. The latter technique employs a flexible carbon screen-printed electrode (SPE) to facilitate the on-site detection of STI. By establishing a pathologically meaningful threshold, relatively simple optical and amperometric assays tendered the diagnosis in a straightforward ‘True’/‘False’ digital format. Only the simultaneous presence of elevated levels of both enzyme inputs would thus trigger a positive diagnosis. Moreover, an interference investigation is performed that employs circulating levels of potential interferents. Such an enzyme cascade and enzymatically-processed biochemical information offer promise for point-of-care injury screening where a rapid determination of pathological situations is a prime consideration.

A new technique for dispersion mapping of low dispersion fibers is reported. A counter-colliding pump-probe power transfer is used to achieve localized four-photon mixing at arbitrary waveguide locations. By controlling the position and strength of the counter-colliding interaction, the entire waveguide length is scanned to obtain high-resolution dispersion map. The new technique is used to demonstrate meter-scale dispersion retrieval in highly nonlinear fibers for the first time.

Continuously tunable optical delay lines based on parametric process in optical fibers are described theoretically and demonstrated experimentally. Performance limits are outlined and compared to alternative approaches capable of continually adjustable delay management. The current record of 105 ns tunable optical delay at 10 Gb/s is presented, with a delay-bandwidth product of 1055.

A new wearable electrochemical sensor for monitoring the pH of wounds is introduced. The device is based on the judicious incorporation of a screen-printed pH potentiometric sensor into bandages. The fabrication of this sensor, which uses an electropolymerized polyani- line (PANi) conducting polymer for pH sensing, combines the screen-printing fabrication methodology with all- solid-state potentiometry for implementation of both the reference and the working electrodes. The pH bandage sensor displays a Nernstian response over a physiological- ly relevant pH range (5.5-8), with a noteworthy selectivi- ty in the presence of physiological levels of most common ions. The bandage-embedded sensor can track pH fluctu- ations with no apparent carry-over effect. The sensor dis- plays good resiliency against mechanical stress, along with superior repeatability and reproducibility. The in vitro performance of the device was successfully evaluated using buffer solutions emulating the composition of a wound. The novel pH-sensitive bandages facilitate new avenues towards the realization of telemedicine.

We investigate the synthesis of flat parametric response of a dual-pumped device with a distant pump separation ranging from 130 to 180 nm. The Raman contribution to the nonlinear polarization introduced predictable gain ripple and dispersion fluctuation along the highly nonlinear fiber had to be precisely accounted for. A 3-dB equalized gain was observed over 100 nm using 130-nm separated pumps. Record gain bandwidth of 155 nm was also measured for the first time.

A continuously tunable optical delay line based on a two-pump parametric process in a highly nonlinear fiber providing 400.5-ns range for a 10-Gb/s optical signal is reported. This record 4005-bit delay used fixed dispersion elements, compatible with requirements for fast delay reconfiguration. The large delay range was made possible by partial dispersion slope cancelation.

A record continuous-wave one-pump fiber-optic parametric amplifier was constructed using localized dispersion measurement of highly nonlinear fiber. Record 3-dB equalized gain bandwidth of 120 nm was measured for the first time. The second amplifier constructed using suboptimal segments of the identical fiber spool did not replicate the wideband performance, confirming the importance of accurate dispersion fluctuating fiber map.

A continuously tunable optical delay line providing over 105 ns of 10-Gb/s optical channel is reported using a two-pump parametric process in a nonlinear optical fiber. Performance limits are measured and compared with recently reported all-optical delay results. The figure of merit defined by the delay-bandwidth product is 1055.

This article describes the fabrication, characterization and application of an epidermal temporary-transfer tattoo-based potentiometric sensor, coupled with a miniaturized wearable wireless transceiver, for real-time monitoring of sodium in the human perspiration. Sodium excreted during perspiration is an excellent marker for electrolyte imbalance and provides valuable information regarding an individual's physical and mental wellbeing. The realization of the new skin-worn non-invasive tattoo-like sensing device has been realized by amalgamating several state-of-the-art thick film, laser printing, solid-state potentiometry, fluidics and wireless technologies. The resulting tattoo-based potentiometric sodium sensor displays a rapid near-Nernstian response with negligible carryover effects, and good resiliency against various mechanical deformations experienced by the human epidermis. On-body testing of the tattoo sensor coupled to a wireless transceiver during exercise activity demonstrated its ability to continuously monitor sweat sodium dynamics. The real-time sweat sodium concentration was transmitted wirelessly via a body-worn transceiver from the sodium tattoo sensor to a notebook while the subjects perspired on a stationary cycle. The favorable analytical performance along with the wearable nature of the wireless transceiver makes the new epidermal potentiometric sensing system attractive for continuous monitoring the sodium dynamics in human perspiration during diverse activities relevant to the healthcare, fitness, military, healthcare and skin-care domains.

This article presents the fabrication and characterization of novel tattoo-based solid-contact ion-selective electrodes (ISEs) for non-invasive potentiometric monitoring of epidermal pH levels. The new fabrication approach combines commercially available temporary transfer tattoo paper with conventional screen printing and solid-contact polymer ISE methodologies. The resulting tattoo-based potentiometric sensors exhibit rapid and sensitive response to a wide range of pH changes with no carry-over effects. Furthermore, the tattoo ISE sensors endure repetitive mechanical deformation, which is a key requirement of wearable and epidermal sensors. The flexible and conformal nature of the tattoo sensors enable them to be mounted on nearly any exposed skin surface for real-time pH monitoring of the human perspiration, as illustrated from the response during a strenuous physical activity. The resulting tattoo-based ISE sensors offer considerable promise as wearable potentiometric sensors suitable for diverse applications.

The realization of epidermal chemical sensing requires a fabrication methodology compatible with the non-planarity and irregularities of the human anatomy. This Communication describes the development of printed temporary transfer tattoo (T3) electrochemical sensors for physiological and security monitoring of chemical constituents leading towards the demonstration of ‘electronic skin’.

The development of wearable screen-printed electrochemical sensors on underwater garments comprised of the synthetic rubber neoprene is reported. These wearable sensors are able to determine the presence of environmental pollutants and security threats in marine environments. Owing to its unique elastic and superhydrophobic morphology, neoprene is an attractive substrate for thick-film electrochemical sensors for aquatic environments and offers high-resolution printing with no apparent defects. The neoprene-based sensor was evaluated for the voltammetric detection of trace heavy metal contaminants and nitroaromatic explosives in seawater samples. We also describe the first example of enzyme (tyrosinase) immobilization on a wearable substrate towards the amperometric biosensing of phenolic contaminants in seawater. Furthermore, the integration of a miniaturized potentiostat directly on the underwater garment is demonstrated. The wearable sensor-potentiostat microsystem provides a visual indication and alert if the levels of harmful contaminants have exceeded a pre-defined threshold. The concept discussed here is well-suited for integration into dry- and wetsuits worn by divers and recreational surfers/swimmers, thereby providing them with the ability to continuously assess their surroundings for environmental contaminants and security hazards.

The development of a highly parallel enzyme logic sensing concept employing a novel encoding scheme for the determination of multiple pathophysiological conditions is reported. The new concept multiplexes a contingent of enzyme-based logic gates to yield a distinct ‘injury code’ corresponding to a unique pathophysiological state as prescribed by a truth table. The new concept is illustrated using an array of NAND and AND gates to assess the biomedical significance of numerous biomarker inputs including creatine kinase, lactate dehydrogenase, norepinephrine, glutamate, alanine transaminase, lactate, glucose, glutathione disulfide, and glutathione reductase to assess soft-tissue injury, traumatic brain injury, liver injury, abdominal trauma, hemorrhagic shock, and oxidative stress. Under the optimal conditions, physiological and pathological levels of these biomarkers were detected through either optical or electrochemical techniques by monitoring the level of the outputs generated by each of the six logic gates. By establishing a pathologically meaningful threshold for each logic gate, the absorbance and amperometric assays tendered the diagnosis in a digitally encoded 6-bit word, defined as an ‘injury code’. This binary ‘injury code’ enabled the effective discrimination of 64 unique pathological conditions to offer a comprehensive high-fidelity diagnosis of multiple injury conditions. Such processing of relevant biomarker inputs and the subsequent multiplexing of the logic gate outputs to yield a comprehensive ‘injury code’ offer significant potential for the rapid and reliable assessment of varied and complex forms of injury in circumstances where access to a clinical laboratory is not viable. While the new concept of parallel and multiplexed enzyme logic gates is illustrated here in connection to multi-injury diagnosis, it could be readily extended to a wide range of practical medical, industrial, security and environmental applications.

Experimental and theoretical analyses of the lactate dehydrogenase and glutathione reductase based enzymatic AND logic gates in which the enzymes and their substrates serve as logic inputs are performed. These two systems are examples of the novel, previously unexplored, class of biochemical logic gates that illustrate potential biomedical applications of biochemical logic. They are characterized by input concentrations at logic 0 and 1 states corresponding to normal and abnormal physiological conditions. Our analysis shows that the logic gates under investigation have similar noise characteristics. Both significantly amplify random noise present in inputs, however we establish that for realistic widths of the input noise distributions, it is still possible to differentiate between the logic 0 and 1 states of the output. This indicates that reliable detection of abnormal biomedical conditions is indeed possible with such enzyme-logic systems., PDF, 29 pages

The development of a screen-printed strip-based amperometric biosensor for the determination of myeloperoxidase (MPO) levels is reported. The biosensor utilizes 3,3',5,5'-tetramethylbenzidine (TMB) as a redox mediator to enable high-sensitivity quantification of physiological levels of MPO. A multivariate parameter optimization was performed. Under the optimal conditions, physiological levels of MPO between 3 and 18 U/L were detected in both acetate buffer (pH 4.5) and human serum using flexible screen-printed electrodes (SPE). The potential interference generated by common serum-based electroactive compounds and a similar peroxidase enzyme was also investigated. The proposed detection methodology offers a simpler, more rapid, and cost-effective alternative to conventional MPO immunoassays, thereby leading to further development in point-of-care testing of acute cardiac events.

A biocomputing system composed of a combination of AND/IDENTITY logic gates based on the concerted operation of three enzymes: lactate oxidase, horseradish peroxidase and glucose dehydrogenase was designed to process biochemical information related to pathophysiological conditions originating from various injuries. Three biochemical markers: lactate, norepinephrine and glucose were applied as input signals to activate the enzyme logic system. Physiologically normal concentrations of the markers were selected as logic 0 values of the input signals, while their abnormally increased concentrations, indicative of various injury conditions were defined as logic 1 input. Biochemical processing of different patterns of the biomarkers resulted in the formation of norepi-quinone and NADH defined as the output signals. Optical and electrochemical means were used to follow the formation of the output signals for eight different combinations of three input signals. The enzymatically processed biochemical information presented in the form of a logic truth table allowed distinguishing the difference between normal physiological conditions, pathophysiological conditions corresponding to traumatic brain injury and hemorrhagic shock, and abnormal situations (not corresponding to injury). The developed system represents a biocomputing logic system applied for the analysis of biomedical conditions related to various injuries. We anticipate that such biochemical logic gates will facilitate decision-making in connection to an integrated therapeutic feedback-loop system and hence will revolutionize the monitoring and treatment of injured civilians and soldiers.

An S-band tunable optical source based on highly-efficient parametric conversion is investigated. Generation of a continuous-wave 2.5W source that is tunable over 1470–1520nm is demonstrated.

A record continuous-wave one-pump fiber-optic parametric amplifier with a 4-dB equalized gain bandwidth over 140nm was constructed. The importance of employing an accurate dispersion fluctuation map in the synthesis of wideband equalized parametric response was experimentally verified.

Raman-induced gain distortions in broadband (pump separations of 132 and 155nm) double-pumped parametric amplifiers are theoretically and experimentally analyzed. A gain profile possessing 100nm of 3dB ripple and 140nm of 4.7dB ripple is demonstrated.

Efficient generation of a cascade of four-wave mixing products using a low-dispersion highly nonlinear fiber is demonstrated. The measured optical frequency comb (with a spacing of 100 GHz) spans over more than 350 nm.

We present an RF-driven two-stage 40 GHz RZ pulse source based on self-phase modulation and a fiber optic parametric amplifier, for generation of 1.1 ps pulses, and demonstrate generation of OTDM data up to 320 Gb/s.

A record 730 nm parametric conversion in silica fiber from the near-infrared to the short-wave infrared band is reported and analyzed. A parametric gain in excess of 30 dB was measured for a signal at 1300 nm (with corresponding idler at 2030 nm). This conversion was performed in a travelling single-pass one-pump parametric architecture and high efficiency is achieved by a combination of high peak power and a nonlinear fiber with a reduced fourth-order dispersion coefficient.

The development and analytical characterization of a novel ion-selective potentiometric cell in a temporary-transfer tattoo platform for monitoring ammonium levels in sweat is presented. The fabrication of this skin-worn sensor, which is based on a screen-printed design, incorporates all-solid-state potentiometric sensor technology for both the working and reference electrodes, in connection to ammonium-selective polymeric membrane based on the nonactin ionophore. The resulting tattooed potentiometric sensor exhibits a working range between 10(-4) M to 0.1 M, well within the physiological levels of ammonium in sweat. Testing under stringent mechanical stress expected on the epidermis shows that the analytical performance is not affected by factors such as stretching or bending. Since the levels of ammonium are related to the breakdown of proteins, the new wearable potentiometric tattoo sensor offers considerable promise for monitoring sport performance or detecting metabolic disorders in healthcare. Such combination of the epidermal integration, screen-printed technology and potentiometric sensing represents an attractive path towards non-invasive monitoring of a variety of electrolytes in human perspiration.

Increasing security needs require field-deployable, on-the-spot detection tools for the rapid and reliable identification of gunshot residue (GSR) and nitroaromatic explosive compounds. This manuscript presents a simple, all-solid-state, wearable fingertip sensor for the rapid on-site voltammetric screening of GSR and explosive surface residues. To fabricate the new Forensic Fingers, we screen-print a three-electrode setup onto a nitrile finger cot, and coat another finger cot with an ionogel electrolyte layer. The new integrated sampling/detection methodology relies on 'voltammetry of microparticles' (VMP) and involves an initial mechanical transfer of trace amounts of surface-confined analytes directly onto the fingertip-based electrode contingent. Voltammetric measurements of the sample residues are carried out upon bringing the working electrode (printed on the index finger cot) in direct contact with a second finger cot coated with an ionogel electrolyte (worn on the thumb), thus completing the solid-state electrochemical cell. Sampling and screening are performed in less than four minutes and generate distinct voltammetric fingerprints which are specific to both GSR and explosives. The use of the solid, flexible ionogel electrolyte eliminates any liquid handling which can resolve problems associated with leakage, portability and contamination. A detailed study reveals that the fingertip detection system can rapidly identify residues of GSR and nitroaromatic compounds with high specificity, without compromising its attractive behavior even after undergoing repeated mechanical stress. This new integrated sampling/detection fingertip strategy holds considerable promise as a rapid, effective and low-cost approach for on-site crime scene investigations in various forensic scenarios.

This article describes a new alternative approach to the fabrication of printed electrochemical sensors and biosensors based on the transfer of electrode patterns comprising common conductive and insulating inks from elastomeric stamps to a wide variety of rigid and flexible substrates. This simple, low cost, yet robust methodology is demonstrated to be well-suited for the formation of electrochemical sensors on non-planar substrates and large objects/structures, which have traditionally been off-limits to conventional screen printing techniques. Furthermore, the stamped electrode devices are shown to exhibit electrochemical performance that rivals that of their screen printed counterparts and display resilience against severe mechanical deformation. The stamp transfer approach is further extended to the demonstration of epidermal electrochemical sensors through the transfer of the electrode patterns directly onto the skin. The resulting sensors demonstrate a wide range of usability, from the detection of various physiological analytes, including uric acid on the skin, to the identification of residues originating from the handling of munitions and explosives. The migration of printable electrochemical sensors to non-conventional (non-planar and/or oversized) surfaces provides new opportunities within the personal healthcare, fitness, forensics, homeland security, and environmental monitoring domains.

The integration of a biosensor employing a DNAzyme logic system within a biofuel cell is presented. The self-powered DNAzyme logic biosensor conforms with INH logic operation and generates power output in accordance with a truth table. The new concept of logic-activated DNAzyme by the input signals has wide-ranging implications in the self-powered diagnostics domain.

The ability to assess diverse security threats using a biochemical logic network system is demonstrated. The new biocatalytic cascade, emulating a NOR logic gate, is able to identify the presence of explosive compounds and nerve agents by providing a simple and rapid 'YES'/'NO' alert.

The design and characterization of a microneedle array-based carbon paste electrode towards minimally invasive electrochemical sensing are described. Arrays consisting of 3 × 3 pyramidal microneedle structures, each with an opening of 425 µm, were loaded with a metallized carbon paste transducer. The renewable nature of carbon paste electrodes enables the convenient packing of hollow non-planar microneedles with pastes that contain assorted catalysts and biocatalysts. Smoothing the surface results in good microelectrode-to-microelectrode uniformity. Optical and scanning electron micrographs shed useful insights into the surface morphology at the microneedle apertures. The attractive performance of the novel microneedle electrode arrays is illustrated in vitro for the low-potential detection of hydrogen peroxide at rhodium-dispersed carbon paste microneedles and for lactate biosensing by the inclusion of lactate oxidase in the metallized carbon paste matrix. Highly repeatable sensing is observed following consecutive cycles of packing/unpacking the carbon paste. The operational stability of the array is demonstrated as well as the interference-free detection of lactate in the presence of physiologically relevant levels of ascorbic acid, uric acid, and acetaminophen. Upon addressing the biofouling effects associated with on-body sensing, the microneedle carbon paste platform would be attractive for the subcutaneous electrochemical monitoring of a number of physiologically relevant analytes.

A multi-enzyme biocatalytic cascade processing simultaneously five biomarkers characteristic of traumatic brain injury (TBI) and soft tissue injury (STI) was developed. The system operates as a digital biosensor based on concerted function of 8 Boolean AND logic gates, resulting in the decision about the physiological conditions based on the logic analysis of complex patterns of the biomarkers. The system represents the first example of a multi-step/multi-enzyme biosensor with the built-in logic for the analysis of complex combinations of biochemical inputs. The approach is based on recent advances in enzyme-based biocomputing systems and the present paper demonstrates the potential applicability of biocomputing for developing novel digital biosensor networks.

We report first experimental demonstration of single stage, self-seeded 2-pump fiber optic parametric amplifier for simultaneous wavelength conversions. 320 Gb/s single channel OTDM signal was successfully copied to 5 wavelengths with ≪3 dB Q-factor penalty.