Embroidered electrodes

Knitted and embroidered electrodes were also investigated to stimulate the blood flow and, hence, to reduce the risk of patients developing pressure ulcers if they have to rest in bed for a long period (Schwarz, 2011). A typical knitted electrode is shown in Fig. 2.11. 

Weder, M., Hegemann, D., Amberg, M., Hess, M., Boesel, L., Abacherli, R., Meyer, V., Rossi, R., 2015. Embroidered electrode with silver/titanium coating for long-term ECG monitoring. Sensors 15, 1750—1759. 

In order to achieve improved contact between the electrodes and the hmnan skin, researchers exploited the embroidery technology as the embroidered part is elevated from the textile surface and, hence, a better contact can be achieved (Reichl et al., 2008 Marozas et al., 2011). Here again, silver-coated yams were found to have a low impedance (Weder et al., 2015) and appeared to be unaffected by laundering (Kannaian et al., 2012). Typical electrode designs are depicted in Fig. 2.2. 

In the European Union (EU)-cofunded project ConText, the possibility to record electromyograms in a contactless way was explored. Researchers integrated two embroidered EMG electrodes in a shirt and a vest to perform measurements (Linz et al., 2007). 

Gas sensors are meant to detect volatile compounds when related to the human body these can be odour of urine, armpit sweat or exhaled breath. Seesaard et al. (2015) report on an embroidered sensor that functions as a wearable electronic nose, also referred to as e-nose . Functionalized single-wall carbon nanombe sensing materials were deposited onto interdigitated electrodes that were previously embroidered with electroconductive yam on a fabric substrate (Fig. 2.9). 

Kannaian, T., Neelaveni, R., Thilagavathi, G., 2012. Design and development of embroidered textile electrodes for continuous measurement of electrocardiogram signals. Journal of Industrial Textiles 42 (3), 303—318. 

The inner surface of the medical back belt consists of cotton twill because it is directly applied onto the skin. In the centre of the inner surface the orthopaedic pad, called pelotte, is attached, which consists of foam or silicone material. These orthopaedic pads are often used because they can put pressure on dehned parts of the body to give these parts extra support. They are frequently attached in orthosis or artihcial limbs to prevent the product from shifting during use. This is a very important aspect for the medical back belt because on top of this pad the textile electrodes are embroidered, which have to stay in place, otherwise the treatment will not be effective enough. In the back belt a foam pelotte is used with a protective cover of 100% unbleached cotton. 

The NMES device is connected to the electrodes by soldering and stitching and transmits an electrical impulse to the textile electrodes. The three electrodes on the left side of the pad and the three electrodes on the right side of the pad are connected to each other. A line of embroidered Shieldex silver-plated nylon 117/17 2-ply yam in between the three electrodes makes sure that every electrode will get the impulses that are transmitted from the NMES device. At the back of the orthopaedic pad the electrodes are connected to wires that are interconnected to the NMES device by soldering and stitching. Eurthermore, the orthopaedic pad is hxed by a hook-and-loop fastener to the medical back belt to make sure that it will not slip out... 

At each heartbeat, tiny impulsions are emitted through the skin, which can be detected and converted by conductive electrodes (Pola and Vanhala, 2007), from ionic flow to electrical current (ECG), and more easily measured. The electrodes are made from conductive yams that are often in silver due to its antibacterial properties (Kim et al., 2007) and its biocompatibility or in stainless steel for its resistance to humidity (Schwarz et al., 2011). Manufacturing modes can differ from knitted textiles to embroidered yams. However, CTT Group has favoured the knitted stmcture in order to allow better stretchability and, therefore, better contact with the skin. 

Hertleer et al. (2004) describe a smart suit where stainless steel yams are used to produce knitted electrodes (textrodes), abelt to detect respiration rates and an embroidered coil for a wireless link. 

Figure 7.11 Embroidered EEG cap for epileptics, (a) Electrodes, conductive paths and circuit board (PCB) with all components on one side of the textile, (b) Embroidered eiectrodes without conductive paths and circuit board.

First, automatically altering the embroidery hoop dimensions could improve the possibility of online monitoring of the already embroidered geometry. This feedback control could eliminate many errors and conserve expensive materials like those used in the construction of electrodes. Figure 7.1 la shows some electrodes for EEG monitoring with their embroidered conductive paths and a PCB joined by embroidery on one side of the textile. This is a typical application where the conductive paths and the PCB must be separated from the electrodes, shown in Figure 7.11b. 

Chain stitch embroidery is a modification of the standard embroidery technique. It is technically similar to crochet and is used for further embroidery techniques such as kettle and moss embroidery. Moss embroidery utilizes a single thread system where the needle punches through the base material and pulls the thread out from under the needle, plate side up. The rotary motion of the needle creates a loop on the upper side of the base material. Repeating this technique in a tight area produces a surface with a texture akin to moss (see Fig. 9.13). As this technique produces a high surface area on the front side of the fabric, it has applications in medical textiles including chain stitch embroidered textile electrodes. 

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