# Thermochromic Yams' Application in Fever Detection for Young Children
## 2 Materials and Methods  
### Prototyping  
Fever is characterized as an increase in body temperature that exceeds the typical daily variation. The core temperature is usually defined as the temperature measured inside the pulmonary artery. However, because of the impracticality of accessing deep tissue measuring locations, physicians have resorted to using alternative sites such as the axilla, skin, beneath the tongue, rectum, and tympan membrane to monitor body temperature [21]. Forehead thermometers are used at home because of their advantages of convenient instruction, ease of use, safety, comfort, and rapid results [21]. Thus, the designed prototype opted to monitor the body temperature of young children by focusing on the forehead. The newborn's head plays a crucial part in controlling his/her body temperature because of the heat produced by the brain and the heat loss from its surface area. Stothers [22] discovered that wearing a hat can significantly reduce infant heat loss. This is potentially associated with the risks of hypothermia, a significant and potentially dangerous drop in body temperature. Therefore, the designed prototype utilized a hat as the medium for applying the thermochromic materials. Figure 1 illustrates the sketch and working mechanism of the fever monitor hat designed for young children. We investigated the thermochromic yarn market and identified a provider, Jinhaosheng Textile Co. Ltd., that sold synthetic yarns coated with encapsulated thermochromic pigment in various colours. The supplier also allowed us the opportunity to customize the temperature at which the colour change occurred. The yarn is composed of synthetic materials with a 250/2 Denier weight and possesses a somewhat rigid texture. This aligns with the research conducted by [PERSON] et al. [17], who discovered that a thermochromic coating stiffens the fabric and makes it uncomfortable. To ensure the hat's comfort, we utilized 100% cotton yarn with a 30/3 English Cotton Count (177/3 Denier) as the foundation for the entire hat structure, as illustrated in beige colour in Figure 1. In addition, we applied the thermochromic yarn just to the headband area knitted in a rib structure, as shown in purple in Figure 1. The rib structure was implemented on the headband to optimize its elasticity and smoothness. A plating method was employed to guarantee that only the cotton yarn came into direct touch with the skin. This function helps mitigate skin irritation from the thermochromic coating, especially when developing items for young children. The hat operates on the idea that when the body experiences a high temperature, the headband of the hat changes colour as a means of detecting the fever. According to [PERSON] (2018), fever is defined as a temperature equal to or higher than 38.0 \({}^{\circ}\)C for newborns under 30 days old, equal to or higher than 38.1 \({}^{\circ}\)C for infants who are 1 month old, and equal to or higher than 38.2 \({}^{\circ}\)C for infants who are 2 months old. The thermochromic yarn is customized to change colour from purple to white when the temperature reaches 37 \({}^{\circ}\)C, considering the temperature difference between the inner and outer sides of the knitted fabric. Only headbands were knitted for testing purposes in the simulated body temperature settings, as discussed in the following sections, to simplify the operating procedure. Considering that consumers value both comfort and aesthetic aspects, which can significantly impact the performance of colour changes, various combinations of colours, rib structures, and stretch ratios were used to create the knitted samples.