Wearable Self-powered Systems Research Articles

Self-powered wearable graphene fiber for information expression

With the fast development of wearable electronics, portable energy generation devices are attracting our considerable attention. Among them, the wearable self-powered system spontaneously harvesting energy from the environment will be much needed. Herein, a high-performance graphene fiber power generator (GF-Pg) is produced based on graphene oxide (GO) fiber. The GF-Pg has highly oriented GO sheets assembled within the fiber, which provide favorable channels for efficient ion transport and thus harvests energy from the moisture. A single fiber generator unit with a length of less than 1mm and a diameter of 80µm was able to supply a voltage output of 355mV in response to the humidity variation, which could be enhanced to 1.3V by simply increasing the number of device units. Impressively, this moisture-enabled self-powered fiber could be integrated into flexible textiles to realize an information storage/expression based on the breath activated electronic labels of GF-Pg, demonstrating the promising applications in wearable electronics.

All-in-One Shape-Adaptive Self-Charging Power Package for Wearable Electronics.

Recently, a self-charging power unit consisting of an energy harvesting device and an energy storage device set the foundation for building a self-powered wearable system. However, the flexibility of the power unit working under extremely complex deformations (e.g., stretching, twisting, and bending) becomes a key issue. Here, we present a prototype of an all-in-one shape-adaptive self-charging power unit that can be used for scavenging random body motion energy under complex mechanical deformations and then directly storing it in a supercapacitor unit to build up a self-powered system for wearable electronics. A kirigami paper based supercapacitor (KP-SC) was designed to work as the flexible energy storage device (stretchability up to 215%). An ultrastretchable and shape-adaptive silicone rubber triboelectric nanogenerator (SR-TENG) was utilized as the flexible energy harvesting device. By combining them with a rectifier, a stretchable, twistable, and bendable, self-charging power package was achieved for sustainably driving wearable electronics. This work provides a potential platform for the flexible self-powered systems.

Wearable Thermocells Based on Gel Electrolytes for the Utilization of Body Heat.

Converting body heat into electricity is a promising strategy for supplying power to wearable electronics. To avoid the limitations of traditional solid-state thermoelectric materials, such as frangibility and complex fabrication processes, we fabricated two types of thermogalvanic gel electrolytes with positive and negative thermo-electrochemical Seebeck coefficients, respectively, which correspond to the n-type and p-type elements of a conventional thermoelectric generator. Such gel electrolytes exhibit not only moderate thermoelectric performance but also good mechanical properties. Based on these electrolytes, a flexible and wearable thermocell was designed with an output voltage approaching 1 V by utilizing body heat. This work may offer a new train of thought for the development of self-powered wearable systems by harvesting low-grade body heat.

Two dimensional woven nanogenerator

Nanogenerator (NG) plays an important role in harvesting energy from the ambient environment. Here, we have developed a two dimensional woven nanogenerator (WNG), which imitates the textile's woven structure and is composed of two kinds of fibers crossing with each other, one kind of fibers grown with ZnO nanowires (NWs) and the other kind of fibers covered with the ZnO NWs coated with palladium (Pd) on their surface. Depending on the coupled piezoelectric and semiconducting properties of ZnO, it can generate electricity driven by the external tiny mechanical force such as tiny wind, sounds. The open-circuit voltage and short-circuit current of the WNG were 3mV and 17pA, respectively. Furthermore, the WNG was successfully used to power a microfiber/ZnO NWs hybrid UV sensor to form a wearable self-powered system, which can quantitatively detect the intensity of UV light.