Thermal management of flexible wearable electronic devices integrated with human skin considering clothing effect

Modeling thermal contact resistance at the finger-object interface

“…It is important to note, however, that it is not clear when this assumption breaks down and how to calculate contact resistance between skin and a comparably soft material. This is an interesting area for future research and will increasingly become important in thermal design of mobile, epidermal, and wearable electronics that often interface with the user through a soft exterior [1][2][3][4][5]44]. Lastly, current results support the recent idea of Sripada et al [4], that a silicone gel finger can reasonably well mimic the thermal response of its human counterpart to short contact (a few seconds) with colder or hotter hard objects.…”

“…Despite these simplifications, the CMY model agrees well with measured values of thermal contact resistance for many contacting hard surfaces [24,26]. In adopting Equation (5) for contact resistance calculations between a human finger and a barium fluoride (BaF 2 ) crystal, Ho and Jones [27] acknowledged that this model has a rather limited ability to predict this value for a soft-hard material interface under the application of light pressure in the range of 1-10 kPa (Equation (5) is valid for P greater than 35 kPa. In 1997, Parihar and Wright [28] brought up similar concerns about the adequacy of Equation (5) for predicting contact resistance of an elastomermetal interface.…”

“…Based on our everyday tactile observations described above, we can expect that R c depends on surface roughness, applied force, as well as mechanical and thermal properties of the skin and the contacting material. Since quantifying the contact resistance is important for design of electronics [2][3][4][5][6], thermal displays [7], artificial hands [8], haptic devices [9], and wearable thermoelectric devices [10,11], it is important to know how to combine these physical parameters to model the value of R c .…”

“…σ % σ skin . With this assumption and substitution of the range of skin properties indicated in Table 1 into Equations (5) and (6), Figure 3(a) shows that PM model predictions are in remarkably good agreement with data for finger contact with an aluminum plate from Maamir et al [12]. This agreement is not surprising since Equation (6) was obtained by fitting data on comparably soft materials and metal surface interfaces where k 2 ) k 1 .This notion, however, starts to be questionable for marble (k marble ¼ 2.9 Wm −1 K −1 ) and is not valid for wood (k wood ¼ 0.23-0.4 Wm −1 K −1 [38] that is comparable to k skin ¼ -0.37 Wm −1 K −1 ).…”

Directly Electrospun Carbon Nanofibers Incorporated with Mn3O4 Nanoparticles as Bending-Resistant Cathode for Flexible Al-Air Batteries

“…Flexible and wearable electronic devices have enjoyed rapid development in recent years [1][2][3]. The wearable devices may be placed on wrists as pulse sensors for health monitoring [4], or on legs as muscle sensors [5] for rehabilitation exercises.…”