# Smart Clothing Framework for Health Monitoring Applications
## 3 Proposed Framework for Smart Clothing (Leggings)
### Development in Smart Clothes Sensor Materials
#### 3.5.1 Carbon-Based Sensor Materials  
Graphite is a form of carbon that can be used for developing pencil-on-paper electronics. It has become popular due to its good electrical- and heat-conducting properties, light weight and being disposable and flexible [112, 113]. Graphite flakes deposited on a paper surface and drawn traces have been used as resistors in resistor-capacitor (RC) filters and transistors. The presence of structural edges in graphite flakes increases the strain-induced resistance variation of traces, making them appropriate for strain gauges. Further overlaps in graphite flakes are developed by compressing the trace that leads to a decreasing resistance. Graphene has attracted significant research interest for use in smart clothing due to its outstanding electrical, mechanical, optical transmittance, and thermal properties [114, 115, 116, 117]. It acts as a platform for both interconnects and active devices such as flexible and stretchable transistors and sensors [115]. It has the ability to interact with oxygen-containing groups in textile fibres and is used as a part of textile rather than forming only a surface coating [118]. Graphene can be used as an electrode material for capacitors. Graphene is a useful material for wearable sensors as it contains huge microribbons to adjust the balance between sensitivity and stretchability. Graphene-based ink and an inkjet-printing process were used by researchers at the University of Cambridge to print integrated circuits onto fabric [119]. The researchers experimented using low-cost and sustainable graphene, and other 2D materials containing low-boiling inks printed on polyester fabric (Figure 16). It was observed that the durability and performance of the printed devices were improved by modifying the roughness of the fabric. Researchers from the school of Engineering at The University of British Columbia developed a low-cost graphene-based sensor that can be integrated into textile and composite materials. A microscopic sensor embedded into woven yarns was stretched and used for monitoring human health and detecting motion. A dip-coating process was applied to fabricate a cost effective, tuneable and stretchable sensor on spaxy yams coated with graphene nanoplatelets (GnP). Protecting the conductive layer against harsh conditions, the SpX/GnP was wrapped into a stretchable silicone rubber (SR) sheath, allowing for the fabrication of wearable sensors [120]. A consortium of European academics have discovered a way to coat fabric with graphene to create electronic textiles. They deposited graphene onto a copper foil and then  
Figure 15: Sensor materials for smart clothing. transferred it onto fibres, paving the way for integrating transportable electronic devices into fabrics. This technology inspired the creation of a T-shirt with GPS capabilities, having a hoodie act as the phone or upholstery for playing music files [121]. A supercapacitor connected to a solar cell to be laser printed directly onto textiles produces an efficient, washable and self-powering smart fabric. Graphene oxides (GOs), amorphous silicon solar module, spandex nylon lycra matte fabrics and Polyvinyl alcohol (PVA)/Sulphur acid (H\({}_{2}\)SO\({}_{4}\)) are used as electrolytes in developing laser printed graphene-based supercapacitors [122]. Polydimethylsiloxane (PDMS) was coated on one side of the fabrics and the other side was coated with a GO/Matte binder to form a thin coating. A graphene-coated textile was fabricated in [123] using a wearable strain sensor. An elastic silicone and polydimethylsiloxane (PDMS) were used to encapsulate the textile. A conductive network was established during stretching with vertical and horizontal fibres of the textile. The sensor without having encapsulation provides a low-cost and scalable fabrication method by extending it to other woven fabrics. The high sensitivity, long-term stability and great comfortability of the sensor allow the real-time monitoring of human physiology activities.