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Advances in several engineering fields have led to a trend toward miniaturization and portability of wearable biosensing devices, which used to be confined to large tools and clinical settings. Various systems to continuously measure electrophysiological activity through electrical and optical methods are one category of such devices. Being wearable and intended for prolonged use, the amount of noise introduced on sensors by movement remains a challenge and requires further optimization. User movement causes motion artifacts that alter the overall quality of the signals obtained, hence corrupting the resulting measurements. This paper introduces a fully wearable optical biosensing system to continuously measure pulse oximetry and heart rate, utilizing a reflectance-based probe. Furthermore, a novel data-dependent motion artifact tailoring algorithm is implemented to eliminate noisy data due to the motion artifact and measure oxygenation level with high accuracy in real time. By taking advantages of current wireless transmission and signal processing technologies, the developed wearable photoplethysmography device successfully captures the measured signals and sends them wirelessly to a mobile device for signal processing in real time. After applying motion artifact tailoring, evaluating accuracy with a continuous clinical device, the blood oxygenation measurements obtained from our system yielded an accuracy of at least 98%, when compared to a range of 93.6%-96.7% observed before from the same initial data. Additionally, heart rate accuracy above 97% was achieved. Motion artifact tailoring and removal in real time, continuous systems will allow wearable devices to be truly wearable and a reliable electrophysiological monitoring and diagnostics tool for everyday use.

Flexible sensors composed of carbon nanostructures and elastic materials have been developed for healthcare monitoring, environmental monitoring, disposable biochemical or electrochemical sensors, and many other applications. Fabrication approaches for such sensors and their advantages and current issues related to patterning high‐performance flexible sensors are reviewed. A focus is placed on patterning techniques for carbon‐based flexible sensors including carbon nanotubes, graphene, and other carbon nanostructures. First, novel patterning techniques for nanomaterials are described, along with their current challenges. Next, emerging flexible sensors including humidity, temperature, strain, and pressure sensors are discussed. Finally, the challenges and perspectives for flexible sensors are addressed.

Microelectrodes for detection of chemicals present several advantages over conventional sized electrodes. However, rapid and low-cost fabrication of microelectrodes is challenging due to high complexity of patterning equipment. We present the development of a low-cost, customizable inkjet printer for printing nanomaterials including carbon nanotubes for the fabrication of microelectrodes. The achieved spatial resolution of the inkjet printer is less than 20 µm, which is comparable to advanced commercially available inkjet printers, with the advantage of being low-cost and easily replicated.

This paper presents a two dimensional force sensor fabricated on PDMS nanocomposite, with patterned carbon nanotubes (CNTs) acting as a force sensing unit. A novel fabrication method is composed of inkjet printing of CNTs onto polyethylene terephthalate (PET) and subsequent transfer of the CNT patterns to PDMS, resulting in a CNT-elastomer nanocomposite that is flexible and conductive. This approach allows patterning of a large-area conductive carbon nanotube pattern on PDMS. The achieved sheet resistance of the transferred patterns on PDMS was 1.2k/ when printed 35 times, using an office inkjet printer. The fabricated sensor changes its resistance when force is applied perpendicularly to the sensor. A two dimensional force sensor, working on the principle of compression-induced deformation was fabricated and characterized with achieved resolution of four sensing cells per cm2. Additionally, we demonstrate a two dimensional flexible force sensor capable of creating a pressure map of the applied force. Together with inkjet printing, this pattern transfer process represents a highly effective patterning technique for embedding carbon nanotubes in PDMS. Display Omitted A transfer printing technique has been developed to pattern embedded carbon nanotubes onto PDMS.Patterns show good uniformity, forming an embedded CNT network.A highly flexible two dimensional force sensor has been demonstrated, showing the pressure map applied.

© 2019 The Authors Although health, development, and environment challenges are interconnected, evidence remains fractured across sectors due to methodological and conceptual differences in research and practice. Aligned methods are needed to support Sustainable Development Goal advances and similar agendas. The Bridge Collaborative, an emergent research-practice collaboration, presents principles and recommendations that help harmonize methods for evidence generation and use. Recommendations were generated in the context of designing and evaluating evidence of impact for interventions related to five global challenges (stabilizing the global climate, making food production sustainable, decreasing air pollution and respiratory disease, improving sanitation and water security, and solving hunger and malnutrition) and serve as a starting point for further iteration and testing in a broader set of contexts and disciplines. We adopted six principles and emphasize three methodological recommendations: (1) creation of compatible results chains, (2) consideration of all relevant types of evidence, and (3) evaluation of strength of evidence using a unified rubric. We provide detailed suggestions for how these recommendations can be applied in practice, streamlining efforts to apply multi-objective approaches and/or synthesize evidence in multidisciplinary or transdisciplinary teams. These recommendations advance the necessary process of reconciling existing evidence standards in health, development, and environment, and initiate a common basis for integrated evidence generation and use in research, practice, and policy design.

This paper proposes a simple and rapid fabrication of a glucose sensor based on inkjet printing method. A commercially available inkjet printer is used to print carbon nanotubes and polyaniline nanowires for patterning low sheet resistance electrodes and a chemiresistive glucose sensing area, respectively. Enzyme glucose oxidase, in conjunction with platinum nanoparticles were also incorporated into the chemiresistive sensor to generate a two-step catalytic process: in the first step, glucose is catalyzed by the oxidase to produce hydrogen peroxide as a byproduct, and in the second step, platinum nanoparticles catalyze hydrogen peroxide to produce hydroxide ions which causes a local pH change near the site of reaction. Since the conductivity of polyaniline is known to be pH-responsive, the polyaniline layer serves as a chemiresistive sensor to detect the H2O2 concentration which subsequently leads to the quantification of the glucose concentration. The developed inkjet-printed glucose sensor was able to achieve a detection limit of 2 mM and a good linear relationship between current measurements and glucose concentration was obtained. The results indicate that the proposed method to print a simple, rapid, and disposable glucose sensing device can lead to the development of an on-demand printable point-of-care diagnostic kit for glucose measurement.

Evidence-based approaches to sustainability challenges must draw on knowledge from the environment, development and health communities. To be practicable, this requires an approach to evidence that is broader and less hierarchical than the standards often applied within disciplines.

Display Omitted Inkjet printing method was used to pattern a conducting polymer nanowire network.Nanowire morphology and electrical properties were preserved even after printing.A printed chemiresistive pH sensor and hydrogen peroxide sensor were demonstrated.Potential applications include print-and-use disposable biochemical sensors. This work reports an inkjet printing technique for patterning a conducting polymer nanowire network on a flexible film for applications in chemical sensing. The novelty of this work is in the patterning capability of polymer nanowires to form a conducting path. Polyaniline nanowires were chemically synthesized in an aqueous solution and a surfactant was added to lower the surface tension which enabled the printing of the nanowires using a commercially available inkjet printer. The nanowire network-based patterns were printed on a flexible transparency film, and its morphology characterization, patterning ability as well as the electrical properties were investigated. Finally, as a proof-of-concept, a fully-printed chemical sensors were developed by using the proposed printing technique on flexible films. Two types of sensors were fabricated: a pH sensor and a hydrogen peroxide sensor. The results demonstrate that the developed sensors can be utilized as a low cost, disposable, and easily printable chemical sensors. The proposed technology may find applications in the development of a simple print-and-use biochemical sensing kit for potential use in point-of-care diagnostics.

This paper presents a fully inkjet-printed electrochemical sensor on paper which consists of carbon nanotube-printed working, reference, and counter electrodes. The proposed technique aims at low-cost and disposable paper-based electrochemical sensors. First, a carbon nanotube (CNT) ink was inkjet-printed directly on paper, forming a conductive network. Additionally, a hydrophobic barrier was patterned on paper to limit the absorption of liquid to the designed area. The inkjet printing method allows for rapid patterning of electrodes on paper, resulting in a simple and effective electrochemical sensor. The sheet resistance of the CNT-printed paper was as low as 1 k / after 33 prints. A potential step voltammetry method was applied to determine the concentration of the analytes, iron ion (Fe2+) and dopamine (DA), with linear ranges of 10 μM-200 μM and 10 μM-100 μM, respectively. The reported approach for a fully inkjet-printed electrochemical sensor is easy and cheap, and it has a potential for simple and rapid paper-based point-of-care diagnostics. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0121510jss] All rights reserved.

This work presents inkjet printing of carbon nanotubes on a flexible substrate for a sensor application. An inkjet printed carbon nanotube pattern can be used as a conductive trace or an electrode for a low-cost flexible sensor or a printable electronic device. In this work, an office inkjet printer was modified to print an ink solution made of carbon nanotubes to form conductive patterns on a flexible substrate. Preparation of aqueous carbon nanotube ink was investigated and optimized to achieve good dispersion of carbon nanotubes and high conductance of the printed carbon nanotube patterns. Electrical properties of the printed carbon nanotube pattern were also characterized with a flexible substrate. For a sensor demonstration, the printed carbon nanotube electrode was tested as a working electrode of an electrochemical cell. The results show a promising feasibility for inkjet printed sensor applications.

Capacitor-type energy storage is becoming an attractive option as it can be fabricated with simple methods and allows integration into a flexible substrate for wearable applications. Currently, there is a need for reliable and simple fabrication methods that take into account the characteristics of nanomaterials for their controlled deposition. Inkjet printing presents advantageous features because it allows solution-processed materials to be printed with high accuracy and resolution. Therefore, a number of patterning steps can be performed sequentially, thus minimizing the need for lithography or other fabrication methods. We have fabricated a fully inkjet-printed capacitor as energy storage for wearable sensors. We have explored several configurations of capacitors. A parallel plate capacitor is composed of carbon nanotubes that are inkjet printed on PET film to form a compact conductive mat structure. The assembly is composed of two layers of carbon nanotubes separated by a dielectric layer of polymer, as illustrated in the figure (left). The advantage of this design is that it does not require an electrolyte to function and can be printed on flexible substrate such as PDMS. On the other hand, a supercapacitor configuration achieves higher energy storage, power density, and is also of simple construction [1]. The supercapacitor type is constructed by printing carbon nanotubes and subsequently by electrodepositing a metal oxide. It is finally assembled with a separator membrane for ion conduction and filled with electrolyte, as shown in the figure (right). The charge storage based on the redox reactions of the metal oxide is mainly responsible for its capacitance [2]. The energy storage and power density of the supercapacitor are greatly improved with the use of carbon nanotube electrodes, because of the high surface area of carbon nanotubes. We demonstrate the capacitor as a charge storage component that is integrated in a wearable system. Moreover, our inkjet printing system precisely prints a network of carbon nanotubes. We show that the inkjet-printed capacitors provide a rapid and reliable fabrication for wearable systems. References [1] M. Zhi, C. Xiang, J. Li, M. Li, and N. Wu, Nanoscale, 5, 72–88 (2013). [2] X. Zhang et al., ACS Nano, 5, 2013–2019 (2011). Figure 1

Heather Tallis, Jane Lubchenco and 238 co-signatories petition for an end to the infighting that is stalling progress in protecting the planet.

We present a fully inkjet-printed electrochemical sensor on paper, which uses inkjet-printed carbon nanotubes as the working, counter, and reference electrodes. Although paper-based electrochemical sensors have been demonstrated previously, our method of fabrication is both faster and cheaper and fully inkjet-printed. Due to its superior patterning ability, inkjet printing allows for the fabrication of on-demand paper-based electrochemical sensors without the use of templates or post-deposition photolithography. Additionally, in combining inkjet printing with an exciting material like carbon nanotubes rather than common metals (i.e. gold and silver), the fabrication cost is further reduced, and the possibility for mechanically flexible sensors becomes a reality. The use of paper as a substrate offers many advantages over other possible rigid substrates as well as flexible polymer substrates. Of course, paper is indeed a renewable resource and thus is a very cost-effective substrate for fabrication of disposable sensors. Additionally, paper is naturally flexible, preventing damage to the sensor upon external stress during use. Finally, paper is a great candidate for microfluidic applications due to its superb ability to transport liquids. The fabrication process is remarkably simple. The electrode design was developed using any drawing software or CAD. Multi-walled carbon nanotubes (MWCNTs) were dispersed in deionized (DI) water using sodium dodecyl sulfate (SDS), an anionic surfactant. More specifically, a bottle containing 10 mg/ml of MWCNTs and 8 mg/ml of SDS was sonicated for 30 minutes and centrifuged at 12,000 rpm for 5 minutes. The carbon nanotube ink was then injected into a clean ink cartridge and printed using an office inkjet printer. In order to ensure proper functionality, a low electrode resistance was necessary. This was achieved by printing the carbon nanotube ink multiple times to reduce the sheet resistance. We were able to achieve less than 2 k-ohm/square with 20 prints on paper. The sensor was tested with various concentrations of FeSO4 in 0.1 M H2SO4. A simple potentiostat circuit was used along with a LabView FieldPoint module for voltage control and current measurement. Potential step voltammetry was employed and the saturation current was used as a means to determine analyte concentration.

Printing becomes an emerging manufacturing technology for mechanics, electronics, and consumer products. Carbon nanotubes have recently been used as a material for sensors and electrodes due to their unique electrical and mechanical properties. Printed electrodes and conductive traces particularly offer versatility of fabricating low-cost, disposable, and flexible sensors and devices. While screen-printing has been a conventional method for printing conductive traces and electrodes, inkjet-printing recently attracts a wide attention due to its unique advantages including no template requirement, rapid printing at low cost, on-demand printing capability, and precise control of the printed material. Computer generated conductive trace or electrode patterns can simply be printed on a flexible substrate with proper conductive ink. However, for inkjet-printing of nanotubes to form conductive traces and electrodes, there are few challenges that need to be addressed. One is nanotube dispersion in an ink base solution while others include adjusting surface tension and controlling viscosity of the ink and treating the surface of the printing substrate. This work presents carbon nanotube ink preparation and its demonstration in chemical sensing along with our recent achievements. It is essential to disperse carbon nanotubes to make a carbon nanotube ink. In our previous work, we have demonstrated an inkjet printed electrochemical sensor using an office HP inkjet printer and a carbon nanotube ink. Sodium dodecyl sulfate (SDS) was used as a dispersant and a surfactant in preparing the carbon nanotube ink. It should be noted that that a ratio of SDS concentration and carbon nanotube concentration would be an important factor determining the sheet resistance of a printed carbon nanotube pattern. A preliminary test result confirmed that there would be an optimum SDS:CNT ratio. For flexible sensor applications, sheet resistance change of the printed carbon nanotube patterns on a flexible substrate was measured for varying curvatures of the substrate. For a curvature up to 0.36 cm-1, the sheet resistance increase was less than 2.5% showing that the printed carbon nanotube patterns could be used for a flexible and printed sensor. Using the developed technologies, a fully printed carbon nanotube sensor on a flexible substrate will be demonstrated for chemical and biological sensing.

Land use, watershed processes, and coastal biodiversity are often intricately linked, yet landsea interactions are usually ignored when selecting terrestrial and marine reserves with existing models. Such oversight increases the risk that reserves will fail to achieve their conservation objectives. The conceptual model underlying existing reserve selection models presumes each site is a closed ecological system, unaffected by inputs from elsewhere. As a short-term objective, we recommend extending land-conservation analyses to account for effects on marine biodiversity by considering linkages between ecosystems. This level of integration seems feasible and directly relevant to agencies and conservancies engaged in protecting coastal lands. We propose an approach that evaluates terrestrial sites based on whether they benefit or harm marine species or habitats. We then consider a hypothetical example involving estuarine nurseries. Whether this approach will produce more effective terrestrial reserves remains to be seen.