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BIOTEX—Biosensing Textiles for Personalised Healthcare Management

Textile-based sensors offer an unobtrusive method of continually monitoring physiological parameters during daily activities. Chemical analysis of body fluids, noninvasively, is a novel and exciting area of personalized wearable healthcare systems. BIOTEX was an EU-funded project that aimed to develop textile sensors to measure physiological parameters and the chemical composition of body fluids, with a particular interest in sweat. A wearable sensing system has been developed that integrates a textile-based fluid handling system for sample collection and transport with a number of sensors including sodium, conductivity, and pH sensors. Sensors for sweat rate, ECG, respiration, and blood oxygenation were also developed. For the first time, it has been possible to monitor a number of physiological parameters together with sweat composition in real time. This has been carried out via a network of wearable sensors distributed around the body of a subject user. This has huge implications for the field of sports and human performance and opens a whole new field of research in the clinical setting.

A Wearable Sensor for Measuring Sweat Rate

Wearable sensors present a new frontier in the development of monitoring techniques. They are of great importance in sectors such as sport and healthcare as they enable physiological signals and biological fluids, such as human sweat, to be continuously monitored. Until recently this could only be carried out in specialized laboratories using cumbersome and often expensive devices. Sweat monitoring sensors integrated onto textile substrates are not only innovative but they also represent the first attempt to use such an idea in a system that will be worn directly on the body. This study outlines the development of a wearable sweat-rate sensor integrated onto a textile.

Water sorption by anhydrous ionic liquids

The kinetics of water vapour sorption by several anhydrous hydrophobic and hydrophilic ionic liquids (ILs) were gravimetrically determined at 25 °C and two levels of humidity, namely 43 and 81%. A simple equation was used to fit the data. The kinetic parameters obtained from the different ILs were compared and the differences were related to the IL structures. Results showed that even hydrophobic ILs absorb water at an unexpected speed.

Textile sensors to measure sweat pH and sweat-rate during exercise

Sweat analysis can provide a valuable insight into a persons well-being. Here we present wearable textile-based sensors that can provide real-time information regarding sweat activity. A pH sensitive dye incorporated into a fabric fluidic system is used to determine sweat pH. To detect the onset of sweat activity a sweat rate sensor is incorporated into a textile substrate. The sensors are integrated into a waistband and controlled by a central unit with wireless connectivity. The use of such sensors for sweat analysis may provide valuable physiological information for applications in sports performance and also in healthcare.

SWAN-iCare: A smart wearable and autonomous negative pressure device for wound monitoring and therapy

The EU FP7 SWAN-iCare project aims at developing an integrated autonomous device for the monitoring and the personalized management of chronic wounds, mainly diabetic foot ulcers and venous leg ulcers. Most foot and leg ulcers are caused by diabetes and vascular problems respectively but a remarkable number of them are also due to the co-morbidity influence of many other diseases (e.g. kidney disease, congestive heart failure, high blood pressure, inflammatory bowel disease). More than 10 million people in Europe suffer from chronic wounds, a number which is expected to grow due to the aging of the population. The core of the project is the fabrication of a conceptually new wearable negative pressure device equipped with Information and Communication Technologies. Such device will allow users to: (a) accurately monitor many wound parameters via non-invasive integrated micro-sensors, (b) early identify infections and (c) remotely provide an innovative personalized two-line therapy via non-invasive micro-actuators to supplement the negative pressure wound therapy. This paper describes the main components of the SWAN-iCare system and its potential impact in the area of wound management.

Pressure mapping with textile sensors for compression therapy monitoring.

Compression therapy is the cornerstone of treatment in the case of venous leg ulcers. The therapy outcome is strictly dependent on the pressure distribution produced by bandages along the lower limb length. To date, pressure monitoring has been carried out using sensors that present considerable drawbacks, such as single point instead of distributed sensing, no shape conformability, bulkiness and constraints on patient’s movements. In this work, matrix textile sensing technologies were explored in terms of their ability to measure the sub-bandage pressure with a suitable temporal and spatial resolution. A multilayered textile matrix based on a piezoresistive sensing principle was developed, calibrated and tested with human subjects, with the aim of assessing real-time distributed pressure sensing at the skin/bandage interface. Experimental tests were carried out on three healthy volunteers, using two different bandage types, from among those most commonly used. Such tests allowed the trends of pressure distribution to be evaluated over time, both at rest and during daily life activities. Results revealed that the proposed device enables the dynamic assessment of compression mapping, with a suitable spatial and temporal resolution (20 mm and 10 Hz, respectively). In addition, the sensor is flexible and conformable, thus well accepted by the patient. Overall, this study demonstrates the adequacy of the proposed piezoresistive textile sensor for the real-time monitoring of bandage-based therapeutic treatments.

A dual mode breath sampler for the collection of the end-tidal and dead space fractions

This work presents a breath sampler prototype automatically collecting end-tidal (single and multiple breaths) or dead space air fractions (multiple breaths). This result is achieved by real time measurements of the CO2 partial pressure and airflow during the expiratory and inspiratory phases. Suitable algorithms, used to control a solenoid valve, guarantee that a Nalophan(®) bag is filled with the selected breath fraction even if the subject under test hyperventilates. The breath sampler has low pressure drop (<0.5 kPa) and uses inert or disposable components to avoid bacteriological risk for the patients and contamination of the breath samples. A fully customisable software interface allows a real time control of the hardware and software status. The performances of the breath sampler were evaluated by comparing (a) the CO2 partial pressure calculated during the sampling with the CO2 pressure measured off-line within the Nalophan(®) bag; (b) the concentrations of four selected volatile organic compounds in dead space, end-tidal and mixed breath fractions. Results showed negligible deviations between calculated and off-line CO2 pressure values and the distributions of the selected compounds into dead space, end-tidal and mixed breath fractions were in agreement with their chemical-physical properties.

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.

A D-optimal design to model the performances of dressings and devices for negative pressure wound therapy

A D-optimal design was used to identify and model variables that affect the transit time of wound exudate through an illustrative dressing used for negative pressure wound therapy. Many authors have addressed the clinical benefits of negative pressure wound therapy, but limited information is available on how to assess performances of dressings. In this paper, the transit time of wound exudate through a dressing was chosen as a model parameter to show how experimental design (DOE) can be used for this purpose. Results demonstrated that rate of exudate production, temperature and dressing thickness were the variables with the largest impact on transit time. The DOE approach could be used to model other dressing properties, like for example capability of absorbing excess exudate or breathability.

PDMS Selective Bonding for the Fabrication of Biocompatible All Polymer NC Microvalves

Microvalves are commonly used in microfluidic systems to control precisely the liquid flow. In this paper, the design and fabrication of a normally-closed (NC) all-polymer membrane-type microvalve is described. The microvalve with a diameter and thickness of 5 mm and 3 mm, respectively, is fabricated completely in biocompatible polydimethylsiloxane (PDMS). The opening pressure, which depends on the adhesion between the membrane and the slab, is reduced to the noticeably low value of 3.4 kPa by the surface oxidation of the PDMS layers. This technique in combination with a selective bonding by Polyethylene terephthalate (PET) shadow masking allows for the fabrication of a high reverse pressure microvalve (no flow up to 0.6 MPa reverse pressure). Other major fabrication steps include PDMS doctor-blading and soft lithography in order to fabricate the thin and surface patterned membranes, respectively. The presented microvalve features a minimum flow rate of 1.0 ml min-1.