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Editor's Notes

• #3: This was an MSc level project that raised a few questions that will be addressed in a PhD project by another student.This slide shows the outline of the presentation, which is broken down into three section: Introduction, Experimental, and Results. Which are further broken down as shown.
• #4: The main aim of the project was to print a viable conductive track onto fabrics.Along with this two sub-aims were identified:One to investigate the best printing method for conductive tracks on fabric,And two, to develop a suitable method of testing those conductive tracks.
• #5: The OE-A (Organic and Printed Electronics Association) published a roadmap in 2011 that stated smart fabrics will “open the possibility of body health monitoring with the enhanced comfort for the wearer.”Although there are many applications in medicine, there are also applications within the sports and Defence/Emergency Services sectors, leisure and many others. At the risk of sounding cheesy, the list is endless.
• #6: Medical applications include;Smart Bandages,Intelligent Gloves for surgeons,Strain-sensing supports for recovering patients.Sport;Real-time telemetry for coaches,Feedback systems for athletes.Defence/Emergency Service;Vital signs beamed over the battlefield/scene,Lightened load by integrating clothing with components,Power sources integrated in to clothing also.
• #7: Throughout the project the tracks were printed onto fabrics using a presco screen press, with two main design of screen,The first is a straight line track, which in the preliminary section had widths between 0.2 mm and 2 mm, 110 mm in length.The second design is a looped circuit, this will be discussed later on.
• #8: Three of the fabrics were provided by rainbow jerseys, these were made of the following: Supplex, Meryl and Cotton blended with Lycra. The fourth fabric mentioned above is a 100% cotton t-shirt. The fabrics from rainbow jerseys were used in the preliminary and main tests, whereas the t-shirt was only used in the preliminary tests.
• #9: For the printing, the effects of printing onto various directions and sides of the fabric was investigated. Prints along the warp and weft of the material were investigated and then the front and back.
• #10: This is the front of the material, the picture is taken over the printed section of the sample without a primer layer
• #11: This is the front of the material, the picture is taken over the non-printed section of the sample without a primer layer
• #12: This is the back of the material, the picture is taken over the printed section of the sample without a primer layer
• #13: This is the back of the material, the picture is taken over the printed section of the sample without a primer layer
• #14: This picture shows the transition points between the primer layer and printed areas, the difference in the surface roughness can be seen with the primer layer on the left of the picture and the printed section at the bottom of the picture.
• #15: This picture shows the sample after washing, as can be seen the printed only section remains intact however the primer and printed layer has had the silver ink removed.
• #16: Preliminary tests were carried out with the intention of finding the problems with methods before final testing took place. And to give an initial investigation into the effect of printing on the weave or warp, and front or back. Another brief investigation was carried out into the characteristics of Carbon/Graphite ink against Silver ink.The main measured parameter of the conductive tracks was the conductance, and as a result two basic preliminary tests were carried out. A straightforward conductance test using nothing but a multimeter, and the second was a conductance test using the multimeter and hounsfield materials tester to stretch the material while testing the conductivity.
• #17: One of the main comparisons was between the carbon/graphite ink and silver ink. As shown in the pictures the carbon prints better than the silver ink, however the resistances were in the region of 10’s of kilo-ohms. The silver ink by comparison had resistances of in the region of just units of ohms. In terms of the material itself the front of the material appeared to give better results, however the printed direction (warp or weft) needed more investigation into repeatability.
• #18: As shown in the picture, the hounsfield materials tester has a sample in its clamps, and the multimeter is positioned ready to be connected to the tracks using crocodile clamps.The effects of stretching were quite inconsistent, some samples broke conductance, and some maintained the same conductance as the unstretched sample.
• #19: Out of all the stretched tests one of the most complete sets of results are shown here, and as expected the track resistance increased proportionally with extension.
• #20: Using the experience of the preliminary phase, three important lessons were learnt these are;Wider tracks give better printingSilver paste gives a lower resistance than carbon/graphite inkThe front of the material gives better resultsA more thorough investigation was then carried out into the following four parameters;Material,Primer Layer,Printed Direction (warp or weft),Mesh resolution.
• #21: Knowing that wider tracks are more conductive, a new mesh design was made, with track widths starting at 2mm and increasing to 10 mm. These tracks are slightly shorter than the preliminary testing and are 95 mm long. Also a winding track was designed which was 6 mm wide and approximately 490 mm long.Of the straight track design three mesh resolutions were used, (61-64), (32-100), (27-120). The numbers refer to the number of lines per cm and the diameter of the wires respectively.Screen resolution had a significant affect on the resistance of the samples with the best results being produced by the more coarse mesh resolutions.
• #22: Throughout the main testing, one ink was used, a silver, commercially available paste. 132 samples were printed, half of those with a primer layer. A third were printed along the weft, leaving two thirds along the weave. There were 44 samples of each material.The primer layer lowered the resistance of the samples, but as can be seen in the next slide caused other problems that need to be addressed in further study.
• #23: The commercially available primer layer had poor adhesion to the silver paste, which lead to the ink breaking off the sample during handling of the sample. This can be seen in the picture, the brighter section is the silver printed onto a primer, whereas the darker section is just the silver paste.
• #24: Part of a feasible conductive track on fabric is the ability to still conduct after washing. As a result this was tested during the main testing phase. All 132 samples were washed and none of them conducted after washing. Furthermore the samples with a primer layer had the silver paste washed off. This can be seen in the picture whereas the other picture shows the sample without a primer layer.
• #25: During the testing and printing phases of the main testing several issues were encountered. With the printing these are;The silver ink was not compatible with the primer layer chosen, which lead to the ink breaking up and limited the testing of the samples, for example they could not be tested on the hounsfield materials tester.The fabrics stretched under the action of the squeegee during printing, which lead to some distorted prints.With the coarser meshes the ink smeared on the top of the fabric after printing.During testing;The strength of the ink caused some inconsistent results with the hounsfield as can be seen in the picture, the sample would stretch except where the ink is resisting the tensile force.As mentioned previously the primer layer caused the ink to break up which meant during testing the samples would not conduct, or completely break up during stretching.
• #26: In conclusion a successful method for printing conductive tracks onto fabrics has been developed, however the ink selected in this study did not perform well under tensile loading. The ink did not survive the washing of the sample, and the primer layer used was not compatible with the ink. All in all the project raised a few questions that need to be addressed in further study, and whilst successful in some areas did not achieve the aim of printing a feasible conductive track onto fabrics as the samples cannot be washed or stretched.
• #27: The main areas that need further investigation have been identified in this slide, a suitable primer layer needs to be found in order to lower the resistance of the conductive tracks. A combination of primer and ink that allows the sample to be washed and stretched will be crucial in printing a feasible conductive track, and eventually extending the range of inks and primers that are feasible will be beneficial.Once a feasible track has been produced, a method of interconnecting tracks within clothing will need to be developed, and finally an investigation into mass production.