Development and washing reliability testing of a stretchable circuit on knit fabric

The smart textiles and wearable technology markets are expanding tirelessly, looking for efficient solutions to create long-lasting products. The research towards novel integration methods and increasing reliability of wearables and electronic textiles (e-textiles) is expanding. One obstacle to be tackled is the washability and the endurance to mechanical stresses in the washing machine. In this article, different layering of thermoplastic polyurethane (TPU) films and knit fabrics are used to integrate three different designs of stretchable copper-based meander tracks with printed circuit boards. The various combinations are washed according to the ISO 6330-2012 standard to analyze their endurance. Results suggest that one meander design withstands more washing cycles and indicate that the well-selected layer compositions increase the reliability. Higher stretchability together with greater durability is accomplished by adding an extra meander-shaped TPU film layer

First responders occupancy, activity and vital signs monitoring - SAFESENS

This paper describes the development and implementation of the SAFESENS (Sensor Technologies for Enhanced Safety and Security of Buildings and its Occupants) location tracking and first responder monitoring demonstrator. An international research collaboration has developed a stateof-the-art wireless indoor location tracking system for first responders, focused initially on fire fighter monitoring. Integrating multiple gas sensors and presence detection technologies with building safety sensors and personal monitors has resulted in more accurate and reliable fire and occupancy detection information. This is invaluable to firefighters in carrying out their duties in hostile environments. This demonstration system is capable of tracking occupancy levels in an indoor environment as well as the specific location of fire fighters within those buildings, using a multi-sensor hybrid tracking system. This ultra-wideband indoor tracking system is one of the first of itsâ kind to provide indoor localization capability to sub meter accuracies with combined Bluetooth low energy capability for low power communications and additional inertial, temperature and pressure sensors. This facilitates increased precision in accuracy detection through data fusion, as well as the capability to communicate directly with smartphones and the cloud, without the need for additional gateway support. Glove based, wearable technology has been developed to monitor the vital signs of the first responder and provide this data in real time. The helmet mounted, wearable technology will also incorporate novel electrochemical sensors which have been developed to be able to monitor the presence of dangerous gases in the vicinity of the firefighter and again to provide this information in real time to the fire fighter controller. A SAFESENS demonstrator is currently deployed in Tyndall and is providing real time occupancy levels of the different areas in the building, as well as the capability to track the location of the first responders, their health and the presence of explosive gases in their vicinity. This paper describes the system building blocks and results obtained from the first responder tracking system demonstrator depicted

Venyvän elektroniikan vaihtoehtoiset valmistus- ja tutkimusmenetelmät

Stretchable electronics are used in wearable applications to implement intelligent features. The main characteristic of stretchable electronics is stretchability enabling deformation required in wearable objects such as bandages and clothes. In this thesis, the stretchable electronics consist of elastic substrates, printed stretchable interconnections, adhesives and rigid modules with traditional electronic components. The modules on the elastic substrate form rigid islands that allow the substrate to stretch. Stretchable electronics can endure only a specific amount of elongation before their electrical interconnections fail. Adhesion and deformation mechanisms in the joint and in the joint area of the module and the substrate affect elongation. The durability of stretchable electronics can be improved by improving adhesion and controlling the deformations via optimizing the structure of the joint and the joint area. In this thesis, the stretchable electronics were studied on several levels. A thermoplastic polyurethane (TPU) film was used as the elastic substrate. Wettability and effectiveness of pre-treatments on wettability were examined. The substrate was investigated by measuring contact angles of droplets with a drop shape analyzer. Adhesion and peel behavior of non-conductive adhesives between the TPU-film and the rigid substrates were studied with a floating roller peel test setup. Finally, tensile testing was used to investigate deformations and elongation of the fabricated stretchable electronics samples. In the tensile test samples, width of the interconnection, the amount of the conductive adhesive and the use of a supportive frame structure were varied. The tests presented new results that can be adopted alone or as whole. The wettability of the TPU-film improved most with a plasma pre-treatment that decreased the contact angles up to 63 percent. The peel tests showed that the sample with one cyanoacrylate adhesive with a primer had the highest momentary bond strength (0,5 N/mm). The high bond strength made the TPU-film elongate during the peeling test. Unlike the tested structural adhesives, an elastic transfer tape adhesive had the most even peeling force during the tests (between 0,2 – 0,3 N/mm) and was the easiest adhesive to process. According to the stress peaking concept, in the tensile testing, when the samples elongated, stress concentrated close to the attached module and broke the samples. The strongest interconnection elongated 91,7 % before failure. The referred sample type had the supportive frame and conductive adhesive only under the contacts. Similarly, according to the concept, the stress exerted on this sample was more uniform compared to the other tensile test samples, which explains the good results

Modellierung und experimentelle Untersuchung von materialintegrierten Sensoren

The thesis is divided in a theoretical and an experimental part. In the theoretical part investigations on the foreign body effect of a sensor in a material in terms of mechanical, thermal and thermo-mechanical loads are done. The second part is based on experiments on the foreign body effect to prove the results of the first part. Therefore temperature and force sensors are integrated in epoxy resin, aluminum and steel

Ubiquitous Computing

The aim of this book is to give a treatment of the actively developed domain of Ubiquitous computing. Originally proposed by Mark D. Weiser, the concept of Ubiquitous computing enables a real-time global sensing, context-aware informational retrieval, multi-modal interaction with the user and enhanced visualization capabilities. In effect, Ubiquitous computing environments give extremely new and futuristic abilities to look at and interact with our habitat at any time and from anywhere. In that domain, researchers are confronted with many foundational, technological and engineering issues which were not known before. Detailed cross-disciplinary coverage of these issues is really needed today for further progress and widening of application range. This book collects twelve original works of researchers from eleven countries, which are clustered into four sections: Foundations, Security and Privacy, Integration and Middleware, Practical Applications