**5. Power Supply for Wearables with Task Offloading Capabilities**

Task-offloading approaches can be efficiently combined with energy harvesting to address the issue of insufficient battery capacity and limited computation resources in IoMT devices and consequently increase the operating time of wearable devices. This is referred to as joint energy harvesting and task offloading. Using this technology, users can extract energy, convert it into useful energy, store it in the appropriate energy-storage device, and use that energy to perform the corresponding local computing and offloading tasks [15,89–91].

As depicted in Figure 4, the offloading algorithm reacts based on two estimations: The energy harvested/stored and the energy demands. Energy harvesting from ambient sources is considered a promising solution that can be used to provide power supply for IoMT devices and thus replace batteries. The most commonly used harvesters for the supply of wearable devices are piezoelectric harvesters, thermoelectric generators, RF harvesters, and solar cells. Table 4 illustrates the amount of power that can be harnessed from different sources, along with some advantages and limitations associated with each.

Ambient light presents the highest power density among other sources, with the possibility of harvesting indoor and outdoor. However, it has limited application due to its restricted availability.


**Table 4.** Available power from different energy sources (literature survey).
