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Typical soil health assessment requires intensive field sampling and laboratory analysis. Although this approach yields accurate results, it can be costly and labor intensive and not suitable for continuous tracking of soil properties. Advances in soil sensor and wireless technologies are poised to replace physical sampling and offline measurement with in-field monitoring. This article reports the development, deployment, and validation of an Internet-of-Things (IoT) system for continuous monitoring of soil health. The end nodes of the proposed system, called soil health monitoring units (SHMUs), are solar powered and can be installed on a field for extended periods of time. Each SHMU transmits soil temperature, moisture, electrical conductivity, carbon dioxide (CO2), and geolocation data wirelessly using long-range wide-area network (LoRaWAN) radio technology. Data are received by a LoRaWAN gateway, which uploads it to a server for long-term storage and analysis. Users can view acquired data through a Web-based dashboard. The following significant experiments were carried out to validate the developed system: 1) a network consisting of eight SHMUs was deployed at an agricultural field site for several weeks and soil health metrics were analyzed using the soil health dashboard; 2) the flexibility of the system was demonstrated by the addition of an extra CO2 sensor allowing an additional variable directly linked to soil health to be recorded; 3) a wireless communication range of 3422 m was estimated at a transmission power of 10 dBm by deploying the developed system on a large field; 4) the average current consumption of a SHMU (including its associated sensors) was estimated to be 13 mA, at this rate, the onboard Li-ion battery is able to sustain a SHMU for several days; and 5) a 7 cm $\times6.5$ cm solar panel was able to fully charge the onboard battery in 14 days while supplying power to the SHMU.

Inefficient soil management is a hindrance to food productivity and a contributing factor to the degradation of soil quality. Despite decades of research confirming the benefits of using sensors in effective soil management and crop yield, they are still not widely used in farms for several reasons including high cost, difficulty in large area deployment, and requirement of labor-intensive wiring. In this paper, we report a low-cost battery-less chipless wireless sensor tag that can be batch-manufactured for large-scale agricultural surveillance. The sensor tag works based on backscattering techniques for the wireless measurements of the volumetric water content (VWC) of the soil. The sensor tag consists of shorted dipole resonators whose resonance frequencies are dependent on the effective permittivity of the VWC of its surrounding soil. The resonant frequency of the sensor tag is measured by an orthogonally polarized reader antenna that observes the peak in the backscattered spectrum. As a proof-of-concept, a sensor tag with two resonators of length 10 cm and 9 cm, is buried at a depth of 10 cm in the soil and is wirelessly read from a free-space distance of 50 cm, to demonstrate its capability to measure the changes in VWC. The resonators of length 10 cm and 9 cm have demonstrated a linear change of −3.92 MHz/VWC and −4.85 MHz/VWC, respectively, within the VWC range 4-27%. By changing the functional passivation layers on the demonstrated sensor tag, this concept can be applied to a wide range of low-cost subsoil sensors for precision agriculture applications.

This work presents a low-cost, passive, flexible, polymeric pump for topical drug delivery which uses wound pH as a trigger for localized drug release. Its operation relies on a pH-responsive hydrogel actuator which swells when exposed to the alkaline pH of an infected wound. The pump enables slow release (

A novel and flexible oxygen sensing patch was successfully developed for wearable, industrial, food packaging, pharmaceutical and biomedical applications using a cost-efficient and rapid prototypable additive inkjet print manufacturing process. An oxygen sensitive ink was formulated by dissolving ruthenium dye and ethyl cellulose polymer in ethanol in a 1 : 1 : 98 (w/w/w) ratio. The patch was fabricated by depositing the oxygen sensitive ink on a flexible parchment paper substrate using an inkjet printing process. A maximum absorbance from 430 nm to 480 nm and a fluorescence of 600 nm was observed for the oxygen sensitive ink. The capability of the oxygen sensitive patch was investigated by measuring the fluorescence quenching lifetime of the printed dye for varying oxygen concentration levels. A fluorescence lifetime decay (τ) from ≈4 μs to ≈1.9 μs was calculated for the printed oxygen sensor patch, for oxygen concentrations varying from ≈5 mg L−1 to ≈25 mg L−1. A sensitivity of 0.11 μs mg L−1 and a correlation coefficient of 0.9315 was measured for the printed patches. The results demonstrated the feasibility of employing an inkjet printing process for the rapid prototyping of flexible and moisture resistant oxygen sensitive patches which facilitates a non-invasive method for monitoring oxygen and its concentration levels.

Phosphate is one of the main nutrients playing many key roles in the human body and plant growth. Because of this essential demand, phosphate is often used as a micronutrient additive in both fertilizers and dietary supplements. However, its excessive amount could result in severe health issues in the human body and the ecosystem of aquatic life. Therefore, there is a need for an inexpensive rapid measurement approach that could assess the optimum level of phosphate by using simple low-cost sensors. Here, for the first time, we demonstrate the use of a nickel oxide modified screen printed carbon (PrC) electrode as a low-cost electrochemical potentiometric phosphate detection sensor. The nickel oxide/oxyhydroxide (NiO/NiOOH)-PrC electrode has been prepared by a facile anodic electrodeposition process onto a screen printed carbon electrode. The characterization performed by field emission scanning electron microscopy (FE-SEM) and energy diffractive X-ray spectroscopy (EDS) techniques confirmed the formation of NiO/NiOOH by significant changes in surface morphology and elemental composition of PrC after electrodeposition. The results exhibited a porous deposited layer containing nickel and an increased oxygen value of the modified electrode as compared to pristine PrC. Potentiometric phosphate detection on the NiO/NiOOH-PrC electrode showed a linear response in the concentration range of 10−6–10−1 M, yielding a slope of −78.48 mV per decade with a fast response time. The electrode demonstrated a stable response with less than 0.8% variability of the recorded potential over 2000 seconds. High durability and reusability of the electrode were confirmed by repeated potentiometric phosphate determination tests over a course of 21 days. Interference tests with chloride, nitrate, sulfate, bromide, acetate, and carbonate solutions revealed very low selectivity coefficients within the range of 10−11–10−2, which indicated a high phosphate-selectivity of the developed sensor. This novel technology provides great potential for future scalable production and applications in portable real-time monitoring of phosphate ions in different precision agricultural and point-of-care diagnostic applications.

In this work, we present a systematic study of laser processing of metallized papers (MPs) as a simple and scalable alternative to conventional photolithography-based processes and printing technologies. Two laser-processing methods are examined in terms of selectivity for the removal of the conductive aluminum film (25 nm) of an MP substrate; these processes, namely direct and indirect laser ablation (DLA and ILA), operate at wavelengths of 1.06 μm (neodymium-doped yttrium aluminum garnet) and 10.6 μm (CO2), respectively. The required threshold energy for each laser processing method was systematically measured using electrical, optical, and mechanical characterization techniques. The results of these investigations show that the removal of the metal coating using ILA is only achieved through partial etching of the paper substrate. The ILA process shows a narrow effective set of laser settings capable of removing the metal film while not completely burning through the paper substrate. By contrast, DLA shows a more defined and selective removal of the aluminum layer without damaging the mechanical and natural fibular structure of the paper substrate. Finally, as a proof of concept, interdigitated capacitive moisture sensors were fabricated by means of DLA and ILA onto the MP substrate, and their performance was assessed in the humidity range of 2-85%. The humidity sensitivity results show that the DLA sensors have a superior humidity sensing performance compared to the ILA sensors. The observed behavior is attributed to the higher water molecule absorption and induced capillary condensation within the intact cellulose network resulting from the DLA process (compared to the damaged one from the ILA process). The DLA process of MP should enable scalable production of low-cost, paper-based physical and chemical sensing systems for potential use in point-of-care diagnostics and food packaging.

We demonstrate, for the first time, a facile and low-cost approach for integrating highly flexible and stretchable microfluidic channels into textile-based substrates. The integration of the microfluidics is accomplished by means of directly embroidering surface-functionalized micro-tubing in a zigzag/meander pattern and subsequently coating it with an elastomer for irreversible bonding. We show the utility of the embroidered micro-tubing by developing robust and stretchable drug-delivery and electronic devices. Controlled drug-delivery platforms with sustained release are achieved through selected laser ablated openings. We further demonstrate a wearable wireless resonant displacement sensor capable of detecting strains ranging from 0 to 60% with an average sensitivity of 45 kHz per % strain by filling the embroidered tubing with a liquid metal alloy, creating stretchable conductive microfluidics with

In this work, we demonstrate a low-cost and flexible solid-state ISE (ion selective electrode) using inkjet-printing for in-field nitrate detection. Three types ISEs of 25, 50, and 140 μm thick ISM (ion selective membrane) are fabricated and characterized. The ISEs exhibit ISM thickness dependent conditioning and stability that thicker ISM leads to longer conditioning but smaller drift; and the converse is true. Whereas, all ISEs present 50-52 mv/dec sensitivity in a wide range of 0.0001M to 0.1M nitrate and ~95% accuracy in soil nitrate detection. The analytical characterizations establish a relationship between fabrication parameters (ISM thickness) and ISE performance, which can be used to tune ISE to different agricultural applications.

Smart Farming represents the application of modern IoT networks into agriculture, leading to what can be called a Third Green Revolution. This paper describes a fully customized hardware platform, with a novel network structure enabled by LoRa and ANT radios, that aims for a low-cost, low power and long range wireless sensor network for smart farming. The hybrid network structure was demonstrated in the Lab and the LoRa portion of the network was tested by deploying four modules across an agricultural site, with data collected over a six months period. The hardware was tested by integrating fabricated nitrate sensors as well as commercially available soil and temperature sensors into the modules. The data collected were made accessible to both researchers and farmers through the cloud.

In this paper, we present a disposable, colorimetric, user-friendly and mass-customizable dermal patch for chronological collection and discrete real-time in situ measurement of sweat secretion over a small area of skin. The patch consists of a laminated filter paper patterned into radially arranged channels/fingers with water-activated dyes at their tips. As channels are filled during perspiration, their tips change color once fully saturated, providing easily identifiable levels of water loss which in turn can be mapped to personal dehydration levels. The patch can be manufactured at low cost in a variety of sizes to allow hydration monitoring for individuals participating in activities under different conditions (intensity, temperature, humidity, etc.). Furthermore, we describe an analytical model that enables mass customization of such a flexible wearable system accommodating a broad range of sweat rates and volumes to generate patch designs that are personalized to an individual’s sweat rate, desired time of usage, and the temporal resolution of the required feedback. As a proof-of-concept demonstration, we characterized laser-fabricated patches that cover (7 cm × 5 cm) area of skin having various wicking materials, thicknesses (180–540 µm), and pore sizes (3–11 µm). Tests were conducted at various flow rates simulating different sweating intensities in the range of 1.5–15 mg/cm2/min. Experimental results for the case of a half-marathon runner targeting 90 min of usage and sweating at a rate of 1.5 mg/cm2/min indicated measurement accuracy of 98.3% when the patch is completely filled., Health: Showing the true color of dehydration Scientists have developed a low-cost wearable skin patch that can monitor the level of perspiration from the human body, and could be used to track hydration levels in athletes, firefighters, and construction workers. Hydration is an important physiological marker, where even small deviations from normal levels can have negative impacts on a human’s cognitive and physical performance and can lead to serious conditions, such as heat exhaustion and stroke. Now, Babak Ziaie, Vaibhav Jain, Manuel Ochoa, and colleagues from Purdue University in the United States have developed a patch made from laminated filter paper patterned with “finger”-shaped channels that contain activated dyes which change color as perspiration increases, providing an inexpensive and adaptable way to monitor hydration levels. The patches can be mass customized into forms that are personalized to an individual.

With the increase in knowledge on the importance of the tumor microenvironment, cell culture models of cancers can be adapted to better recapitulate physiologically relevant situations. Three main microenvironmental factors influence tumor phenotype: the biochemical components that stimulate cells, the fibrous molecules that influence the stiffness of the extracellular matrix, and noncancerous cells like epithelial cells, fibroblasts, endothelial cells, and immune cells. Here we present methods for the culture of carcinomas in the presence of a matrix of specific stiffness, and for the coculture of tumors and fibroblasts as well as epithelial cells in the presence of matrix. Information is provided to help with choice and assessment of the matrix support and in working with serum-free medium. Using the example of a tissue chip recapitulating the environmental geometry of carcinomas, we also highlight the development of engineered platforms that provide exquisite control of cell culture parameters necessary in research and development. © 2019 by John Wiley & Sons, Inc.

Chronic wounds affect over 6.5 million Americans and are notoriously difficult to treat. Suboptimal oxygenation of the wound bed is one of the most critical and treatable wound management factors, but existing oxygenation systems do not enable concurrent measurement and delivery of oxygen in a convenient wearable platform. Thus, we developed a low-cost alternative for continuous O2 delivery and sensing comprising of an inexpensive, paper-based, biocompatible, flexible platform for locally generating and measuring oxygen in a wound region. The platform takes advantage of recent developments in the fabrication of flexible microsystems including the incorporation of paper as a substrate and the use of a scalable manufacturing technology, inkjet printing. Here, we demonstrate the functionality of the oxygenation patch, capable of increasing oxygen concentration in a gel substrate by 13% (5 ppm) in 1 h. The platform is able to sense oxygen in a range of 5–26 ppm. In vivo studies demonstrate the biocompatibility of the patch and its ability to double or triple the oxygen level in the wound bed to clinically relevant levels. Paper-based sensors that measure and adjust oxygen levels within chronic wounds could provide a low-cost solution for accelerating recovery. Such persistent injuries often result from diabetes and long-term hospitalization, and treatment is largely reliant on subjective assessment by healthcare providers. Babak Ziaie of Purdue University and colleagues have developed a proof-of-concept platform for manufacturing inkjet-printed, paper-based dressings that enable close control over oxygen levels in wound tissue—an important factor in the healing process. Their design employs arrays of integrated luminescent oxygen sensors, alongside catalytic regions that can be exposed to hydrogen peroxide to rapidly generate oxygen as needed. The authors demonstrate the potential utility of this approach with both in vitro and in vivo experiments, and they envision this platform as a foundation for future multi-sensor ‘smart’ wound dressings that can be affordably mass produced.

In this work, we present a laser-based fabrication technique for direct patterning of micro-channels consisting of interconnected micro-cracks on soda-lime glass. Using a CO2 laser to deposit energy at a linear rate of 18.75 to 93.75 mJ mm−1, we were able to manipulate the micro-crack formation, while enabling rapid manufacturing and scalable production of cracked-glass microfluidic patterns on glass. At the higher end of the energy deposition rate (93.75 mJ mm−1), the laser fabricated microfluidic channels (1 mm wide and 20 mm long) had extremely fast wicking speeds (24.2 mm s−1, ×10 faster than filter paper) as a result of significant capillary action and laser-induced surface hydrophilization. At the lower end (18.75 mJ mm−1), 3–4 μm wide micro-cracked crevices resulted in an increased mesh/sieve density, hence, more efficiently filtering particle-laden liquid samples. The reproducibility tests revealed an averaged wicking speed of 10.6 ± 1.5 mm s−1 measured over 21 samples fabricated under similar conditions, similar to that of filter paper (∼85%). The micro-cracked channels exhibited a stable shelf life of at least 82 days with a wicking speed within 10–13 mm s−1.

In this Research Article, we demonstrate a facile method for the fabrication of porous-carbon/silver nanocomposites using direct laser writing on polymeric substrates. Our technique uses a combination of CO2 laser-induced carbonization and selective silver deposition on a polyimide sheet to create flexible highly conductive traces. The localized laser irradiation selectively converts the polyimide to a highly porous and conductive carbonized film with superhydrophilic wettability. The resulting pattern allows for selective trapping of aqueous silver ionic ink solutions into the carbonized regions, which are converted to silver nanoparticle fillers upon an annealing step. Elemental and surface morphology analysis via XRD and SEM reveals a uniform coating of Ag nanoparticles on the porous carbon. The Ag/C composite lowers the sheet resistance of the original laser carbonized polyimide from 50 to 0.02 Ω/□. The resulting patterns are flexible and electromechanically robust with less than 0.6 Ω variation in resistance after15000 bending flexion cycles at a radius of curvature of 5 mm. Furthermore, using this technique, we demonstrate the fabrication of a wireless resonant pressure sensor capable of detecting pressures ranging from 0 to 97 kPa with an average sensitivity of -26 kHz/kPa.

The pH level in a chronic wound bed is a key indicative parameter for assessment of the healing progress. Due to fragility and inability to measure multiple wound regions simultaneously, commercial glass microelectrodes are not well-suited for spatial mapping of the wound pH. To address this issue, we present an inexpensive flexible array of pH sensors fabricated on a polymer-coated commercial paper (palette paper). Each sensor consists of two screen-printed electrodes, an Ag/AgCl reference electrode and a carbon electrode coated with a conductive proton-selective polymeric (polyaniline, PANI) membrane. Laser-machining is used to create a self-aligned passivation layer with access holes that is bonded over the sensing and reference electrodes by lamination technology. Characterization of the pH sensors reveal a linear ( r 2 = 0.9734) relationship between the output voltage and pH in the 4–10 pH range with an average sensitivity of −50 mV/pH. The sensors feature a rise and fall time of 12 and 36 s for a pH swing of 8-6-8. The sensor biocompatibility is confirmed with human kertinocyte cells.

Microbial contamination and biofilm formation are serious challenges in water filtration applications. Recently, carbon nanocomposite membranes with modified silver nanoparticles (AgNPs) have attracted much attention as compelling water purification membranes that can deactivate pathogenic bacteria and prevent biofilm formation. However, the effective attachment of AgNPs onto such carbon-based surfaces has proven difficult to accomplish via inexpensive and rapid fabrication processes. In this study, we introduce a simple laser-assisted process that enables rapid surface functionalization and immobilization of AgNPs onto carbon cloth membrane surfaces comprised of woven carbon micro fibers. The laser functionalization provides a unique modification in surface morphology of the fibers by creating nanotextures as well as inducing changes in surface chemistry, all of which increase the physical and chemical bonding of AgNPs onto the surface of carbon fibers. Elemental and surface morphology analysis via XRD, SEM, and EDX reveal a uniform coating and strong attachment of AgNPs onto the laser functionalized carbon surface, even after vigorous mechanical agitations and probe sonication. The analysis showed the samples prepared by the laser functionalization prior to AgNPs coating provided exceptional antibacterial activity and ability to completely eradicate the bacteria within 4 h and resist biofilm formation against pathogenic bacterial strains of Escherichia coli. The developed technology provides new opportunities to develop a scalable, fast, and cost-effective preparation method for producing carbon-based materials/membranes with high antimicrobial activities which can be applied for water purification and other environmental applications.

Chronic wounds are a major health concern and they affect the lives of more than 25 million people in the United States. They are susceptible to infection and are the leading cause of nontraumatic limb amputations worldwide. The wound environment is dynamic, but their healing rate can be enhanced by administration of therapies at the right time. This approach requires real-time monitoring of the wound environment with on-demand drug delivery in a closed-loop manner. In this paper, a smart and automated flexible wound dressing with temperature and pH sensors integrated onto flexible bandages that monitor wound status in real-time to address this unmet medical need is presented. Moreover, a stimuli-responsive drug releasing system comprising of a hydrogel loaded with thermo-responsive drug carriers and an electronically controlled flexible heater is also integrated into the wound dressing to release the drugs on-demand. The dressing is equipped with a microcontroller to process the data measured by the sensors and to program the drug release protocol for individualized treatment. This flexible smart wound dressing has the potential to significantly impact the treatment of chronic wounds.

The development of stretchable sensors has recently attracted considerable attention. These sensors have been used in wearable and robotics applications, such as personalized health-monitoring, motion detection, and human-machine interfaces. Herein, we report on a highly stretchable electrochemical pH sensor for wearable point-of-care applications that consists of a pH-sensitive working electrode and a liquid-junction-free reference electrode, in which the stretchable conductive interconnections are fabricated by laser carbonizing and micromachining of a polyimide sheet bonded to an Ecoflex substrate. This method produces highly porous carbonized 2D serpentine traces that are subsequently permeated with polyaniline (PANI) as the conductive filler, binding material, and pH-sensitive membrane. The experimental and simulation results demonstrate that the stretchable serpentine PANI/C-PI interconnections with an optimal trace width of 0.3 mm can withstand elongations of up to 135% and are robust to more than 12 000 stretch-and-release cycles at 20% strain without noticeable change in the resistance. The pH sensor displays a linear sensitivity of -53 mV/pH (r

This paper reports on a non-invasive, flexible, and wireless pH sensing system for monitoring wound healing progress and identifying the possibility of infection at an early stage. The device consists of a disposable, flexible pH sensor interfaced with a custom-designed, flexible, battery-less and reusable wireless (13.5 MHz, near field communication) data transmitting platform. The sensing electrodes are fabricated by low-cost direct laser scribing of ITO films, resulting in optically transparent sensors which allows for visual inspection of the wound. The sensor accurately measures a physiologically relevant range of pH 4–10 with an average sensitivity of −55 mV/pH.

The purpose of this study was to investigate abamectin, diazinon and chlorpyrifos in apple from the Mahabad of Iran. The influences of several parameters including shadow and sun, geographical directions and varieties of apples, whether they are golden or red type, was also taken into account on the residuals of the pesticides in the samples. The results indicated that sun considerably decreased the concentrations of diazinon and chlorpyrifos in samples exposed to it. Geographical directions are showed to be non-influential on diazinon while they are influential on chlorpyrifos ones. This can be attributed to pesticide spraying time and prevailing wind direction in Mahabad. The pesticides in golden and red varieties showed no significant relations. The apple samples from Mahabad did not contain any abamectin while they contained residuals of diazinon and chlorpyrifos. In some samples the diazinon and chlorpyrifos were above allowed limit according to World Health Organization (WHO) standard.

Controlled mechanical strain or stress on a wound site can promote accelerated neovascularization and cellular proliferation for improved wound healing; however, these mechanical forces have not been properly quantified due to a lack of standardized technique. As a solution, we developed a wireless strain sensor on a commercial wound dressing. The sensor consists of a flexible antenna coil whose resonant frequency changes in response to applied strain. The frequency change of the sensor is observed to be a linear function of applied strain in the range of 0–35%, with an average sensitivity of 150 kHz/%strain and negligible hysteresis. The sensor is fabricated through a simple process that consist of defining a screen-printing mask directly over the wound dressing using laser machining. The fabrication technique can be scaled up for mass production using roll-to-roll methods.

Degradable electronics represent a rapidly emerging field of science and technology with the potential to serve short-term medical implantation applications where the device disappears once its function is complete. Despite many efforts in developing new types of degradable electronics, many of such systems are nonelastic and incompatible with the dynamic motion of native soft/elastic biological tissues. Herein, a photo-crosslinkable hydrogel with integrated electronics that are highly stretchable and degradable in liquid environments is demonstrated. The fabrication process takes advantage of facile laser micromachining of conductive patterns directly onto the hydrogel under ambient conditions and permanent hydrogel-hydrogel bonding. The robustness and degradation rate of hydrogel and the laser-processed encapsulated stretchable circuits is systematically investigated in different solutions under various conditions. Biocompatibility tests with non-neoplastic cells (HMT 3522 S1) and cancer cells (T4-2 and MDA-MB-231) are performed in 2D and 3D cell culture systems to confirm instead of evaluate the safety of the hydrogel and its byproducts during degradation as well as the zinc metal used in this technology. As a proof of concept, a stretchable hydrogel-based device that can be used for remote/wireless delivery of thermal energy into the tissue in contact with the hydrogel is fabricated.