Temperature-and pH-sensitive wearable materials for monitoring foot ulcers

Foot ulcers account for 15% of comorbidities associated with diabetes. Presently, no device allows the status of foot ulcers to be continuously monitored when patients are not hospitalized. In this study, we describe a temperature and a pH sensor capable of monitoring diabetic foot and venous leg ulcers developed in the frame of the seventh framework program European Union project SWAN-iCare (smart wearable and autonomous negative pressure device for wound monitoring and therapy). Temperature is measured by exploiting the variations in the electrical resistance of a nanocomposite consisting of multiwalled carbon nanotubes and poly(styrene-b-(ethylene-co-butylene)-b-styrene). The pH sensor used a graphene oxide (GO) layer that changes its electrical potential when pH changes. The temperature sensor has a sensitivity of ~85 Ω/°C in the range 25°C-50°C and a high repeatability (maximum standard deviation of 0.1% over seven repeated measurements). For a GO concentration of 4 mg/mL, the pH sensor has a sensitivity of ~42 mV/pH and high linearity (R2=0.99)

Printable and flexible graphene pH sensors utilising thin film melanin for physiological applications

The application of highly sensitive pH sensors manufactured in volume at low cost has great commercial interest due to an extensive array of potential applications. Such areas include industrial processing, biotechnology and medical diagnostics particularly in the development of point of care (POC) devices. A novel printable electrochemical pH sensor based on graphene and pigment melanin (PGM), was designed and produced by using a screen printing process that enables up scaling for potential commercial application. We demonstrate a highly sensitive pH sensor (62 mV pH−1  ±  7) over a pH range from 5 to 8, with high stability and superior performance when compared with a number of existing devices and making it suitable for physiological applications

Sensors and Biosensors for C-Reactive Protein, Temperature and pH, and Their Applications for Monitoring Wound Healing: A Review

Wound assessment is usually performed in hospitals or specialized labs. However, since patients spend most of their time at home, a remote real time wound monitoring would help providing a better care and improving the healing rate. This review describes the advances in sensors and biosensors for monitoring the concentration of C-reactive protein (CRP), temperature and pH in wounds. These three parameters can be used as qualitative biomarkers to assess the wound status and the effectiveness of therapy. CRP biosensors can be classified in: (a) field effect transistors, (b) optical immunosensors based on surface plasmon resonance, total internal reflection, fluorescence and chemiluminescence, (c) electrochemical sensors based on potentiometry, amperometry, and electrochemical impedance, and (d) piezoresistive sensors, such as quartz crystal microbalances and microcantilevers. The last section reports the most recent developments for wearable non-invasive temperature and pH sensors suitable for wound monitoring

Novel electronic stretchable materials for future medical devices

L’electrònica convencional basada en el silici te grans dificultats a l’hora de ser implementada en dispositius electrònics que estiguin en contacte amb les corbes i las plasticitat dels teixits del cos humà. Futures aplicacions mèdiques como la pell electrònica, sistemes de alliberació de fàrmac transdèrmic o nous bio-sensors requereixen de sistemes electrònics capaços de ser doblegats, retorçats o enrotllats en superfícies corbes. Tot i els prometedors resultats mostrats por la investigació en electrònica flexible, no hi ha aplicacions comercials directes dins de l’àrea mèdica. La dependència de components només presents en l’electrònica convencional limita el complet desenvolupament d’aquests dispositius posant de manifest la necessitat de trobar nous materials en aquest camp. Amb l’objectiu de potenciar nous sistemes electrònics flexibles, en aquest treball es proposen noves estratègies per proveir de flexibilitat als materials utilitzats en electrònica sense perdre de vista la directa aplicabilitat. Primerament, s’ha estudiat l’aplicació de polímers conductors mitjançant impressió inkjet. Aquesta tecnologia permet l’obtenció de films polimèrics molt fins sobre sistemes flexibles més complexos. Anant un pas més enllà, s’han desenvolupat noves metodologies per poder depositar polímers conductors sobre substrats elastomèrics mantenint el bon rendiment elèctric. Aquesta part culmina amb l’estudi d’un nou polielectròlit per la síntesis del polipirrol basat en l’àcid hialurònic modificat amb grups dopamina. Aquest polielectròlit aporta noves propietats que milloren l’adaptabilitat del polipirrol obtenint nanosuspensions estables que poden ser depositades directament sobre substrats elastomèrics. Centrant-nos en los materials metàl·lics de la electrònica, s’ha desenvolupat un mètode per la deposició selectiva de plata conductora sobre substrats elastomèrics. Les pistes fabricades amb aquest procediment han demostrat un comportament de galga extensomètrica sota deformació mecànica. Finalment la aplicabilitat de las estratègies desenvolupades ha estat avaluada per veure como es poden aplicar en dispositius mèdics actuals y futurs tals como sensors fisiològics, galgas extensomètriques portables para seguiment o nous stents de tràquea electrònics.La implementación de la electrónica convencional basada en el silicio en dispositivos electrónicos que entren en contacto con la plasticidad y las curvas de los tejidos del cuerpo humano presenta serias dificultades. Futuras aplicaciones médicas como la piel electrónica, sistemas de liberación de fármaco transdérmico o nuevos bio-sensores requieren sistemas electrónicos capaces de ser doblados, retorcidos o enrollados en superficies curvas. A pesar de los prometedores resultados mostrados por la investigación en electrónica flexible, muy pocas tecnologías se han visto adaptadas en una aplicación comercial dentro del área médica. Problemas como la dependencia de componentes solo presentes en la electrónica convencional limita el completo desarrollo de estos dispositivos poniendo de manifiesto la necesidad de encontrar nuevos materiales en este campo. Con el objetivo de potenciar nuevos sistemas electrónicos flexibles, este trabajo propone nuevas estrategias para aportar flexibilidad a los materiales empleado para la electrónica sin perder de vista su aplicabilidad. Primeramente, se ha estudiado la aplicación de polímeros conductores usando impresión inkjet. Esta tecnología permite la obtención de films poliméricos muy delgados sobre sistemas flexibles más complejos. Dando un paso más allá, se han desarrollado nuevas metodologías para poder depositar polímeros conductores sobre substratos elastómericos manteniendo un buen rendimiento eléctrico. Esta parte culmina con el estudio de un nuevo polielectrolito para la síntesis del polipirrol basado en el ácido hyaluronico modificado con dopamina. Este polielectrolito aporta nuevas propiedades que mejoran la adaptabilidad del polipirrol obteniendo nanosuspensiones estables que pueden ser depositadas directamente sobre substratos elastómeros. Estudiando también los materiales metálicos en la electrónica, se ha desarrollado un método para la deposición selectiva de plata conductora sobre substratos elastómeros. Las pistas fabricadas con este procedimiento han mostrado un interesante comportamiento de galga extensométrica cuando son sometidas a una deformación. Finalmente, la aplicabilidad de las estrategias desarrolladas ha sido evaluada para ver cómo se puede aplicar en dispositivos médicos actuales y futuros tales como sensores fisiológicos, galgas extenso métricas portables para seguimiento o nuevos stents traqueales electrónicos.Conventional electronics based in rigid and planar silicon wafers presents several difficulties to be implemented in systems where a direct contact with the soft and curved geometries of the tissues of the human body is required. The future medical devices such as electronic skin, transdermal drug delivery systems or novel wearable biosensors requires electronic materials with the ability to be twisted, folded and conformably wrapped onto arbitrarily curved surfaces. Despite the promising results on stretchable electronic research, the applications have not yet been translated into commercial medical devices. The dependence of components still only present in conventional silicon electronics limits the full development of the stretchable strategies, revealing the need for new materials in this field. Aiming to potentiate new electronic stretchable systems, this works proposes novel strategies to provide stretchability to electronic materials always having in mind the final application. Firstly, the study of conducting polymers to be deposited using ink jet printing have been performed. This kind of implementation allows the formation of conductive thin films on more complex flexible systems. Going further, it has been developed novel methodologies using plasma treatments to fabricate conducting polymeric coating on stretchable substrate with good electrical performance. The culmination of this part consisted in the synthesis of polypyrrole with a novel polyelectrolyte based on a hyaluronic acid modified with dopamine groups that allows stable nanosuspension able to directly form a film onto stretchable substrates. Focusing on metallic materials, conductive silver deposition on selective stretchable substrate have been developed. The electrical performance under mechanical deformation revealed strange gauge sensor behaviour of the silver paths with promising applicability in the medical device. Finally, the applicability of the approaches developed in this work have been studied to evaluate its suitability on actual and future applications in the field of medical devices such as physiological sensors, wearable strain gauge sensors or tracheal stent able to monitor deformations

A graphene oxide pH sensor for wound monitoring

This article describes the fabrication and characterization of a pH sensor for monitoring the wound status. The pH sensitive layer consists of a graphene oxide (GO) layer obtained by drop-casting 5 μl of GO dispersion onto the working electrode of a screen-printed substrate. Sensitivity was 31.8 mV/pH with an accuracy of 0.3 unit of pH. Open-circuit potentiometry was carried out to measure pH in an exudate sample. The GO pH sensor proved to be reliable as the comparison with results obtained from a standard glass electrode pH-meter showed negligible differences (< 0.09 pH units in the worst case) for measurements performed over a period of 4 days