Seeking to increase the triboelectric charge density on a friction layer is one of the most basic approaches to improve the output performance of triboelectric nanogenerators (TENGs). Here, we studied the storage mechanism of triboelectric charge in the friction layer and discussed the function of carrier mobility and concentration in the charge-storing process. As guided by these results, a kind of composite structure is constructed in the friction layer to adjust the depth distribution of the triboelectric charges and improve the output performance of TENGs. To further elucidate this theory, a simple TENG, whose negative friction layer is a composite structure by integrating polystyrene (PS) and carbon nanotubes (CNTs) into polyvinylidene fluoride (PVDF), was fabricated, and its performance test was also carried out. Comparing with a pure PVDF friction layer, the composite friction layer can raise the triboelectric charge density by a factor of 11.2. The extended residence time of electrons in the friction layer is attributed to a large sum of electron trap levels from PS.

On the basis of a vertically aligned ultralong Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) nanowire array fabricated using electrospinning nanofibers, we developed a new type of integrated nanogenerator (NG) with ultrahigh output voltage of 209 V and current density of 23.5 μA/cm 2 , which are 3.6 times and 2.9 times of the previous record values, respectively. The output electricity can be directly used to stimulate the frog's sciatic nerve and to induce a contraction of a frog's gastrocnemius. The NG can instantaneously power a commercial light-emitting diode (LED) without the energy storage process. KEYWORDS: Nanogenerator, high output, energy harvesting, PZT nanowires, electrospinning H arvesting clean and renewable energy from the environment is an effective method to response the current energy crisis and power wide distributed nano/microdevices. As a novel energy collector, nanogenerator (NG) exhibits a number of features not shared by the traditional generators, that is, the ones based on ocean tide, river falls, and wind, etc. NG fabricated with piezoelectric nanomaterials can convert tiny and irregular environmental mechanical energy to electricity from sources such as air flowing, heart beating, and so on, which are more popular in our living environment compared to the energy source used for traditional generators as mentioned above.1 Moreover, due to its small size the NG can be effectively integrated with the nano/microscale functional devices to form a self-powered system, which has potential applications in the internet of things, national security, biomedical, and industry areas. In order to improve its output, many attempts have been made ranging from altering piezoelectric materials, that is, ZnO, 14 and so on. Among these systems, many of them need an energy storage unit to make them work properly. This energy storage circuit adds much complexity to the self-powered system and hinders its capacity to work in different tough environments. Here, we report a simple approach of fabricating vertically ultralong Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) nanowire arrays from electrospinning fibers to make a high output NG. Benefiting from the ultralong length of vertical nanowires, the fabricated NG has a maximum output peak voltage of 209 V, which is much higher than the past record of 58 V.2 Also, the NG can output a maximum peak current of 53 μA and current density of 23.5 μA/cm 2 , which is 2.9 times of the recent highest value of 8.13 μA/cm 2 . 15 The output power of our NG can be directly used to stimulate the frog's sciatic nerve and induce a contraction of that frog's gastrocnemius. Moreover, the NG can power a commercial light-emitting diode (LED) instantly without energy storage, which is a considerable progress for the development of selfpowered devices.Previous studies have shown that high piezoelectric coefficient of the fabricating material and integrated parallel and serial connection designs are two major factors to effectively increase NG's output. So, we use PZT, which possesses the highest piezo...

Fabrication of soft piezoelectric nanomaterials is essential for the development of wearable and implantable biomedical devices. However, a big challenge in this soft functional material development is to achieve a high piezoelectric property with long‐term stability in a biological environment. Here, a one‐step strategy for fabricating core/shell poly(vinylidene difluoride) (PVDF)/dopamine (DA) nanofibers (NFs) with a very high β‐phase content and self‐aligned polarization is reported. The self‐assembled core/shell structure is believed essential for the formation and alignment of β‐phase PVDF, where strong intermolecular interaction between the NH2 groups on DA and the CF2 groups on PVDF is responsible for aligning the PVDF chains and promoting β‐phase nucleation. The as‐received PVDF/DA NFs exhibit significantly enhanced piezoelectric performance and excellent stability and biocompatibility. An all‐fiber‐based soft sensor is fabricated and tested on human skin and in vivo in mice. The devices show a high sensitivity and accuracy for detecting weak physiological mechanical stimulation from diaphragm motions and blood pulsation. This sensing capability offers great diagnostic potential for the early assessment and prevention of cardiovascular diseases and respiratory disorders.

A cloth-base wearable triboelectric nanogenerator made of nylon and Dacron fabric was fabricated for harvesting body motion energy. Through the friction between forearm and human body, the generator can turn the mechanical energy of an arm swing into electric energy and power an electroluminescent tubelike lamp easily. The maximum output current and voltage of the generator reach up to 0.2 mA and 2 kV. Furthermore, this generator can be easily folded, kneaded, and cleaned like a common garment.

The low output current density of piezoelectric nanogenerators (PENGs) severely restricts their application for ambient mechanical energy harvest. This has been a key challenge in the development of PENG. Here, to conquer this, based on a piezoelectric material with high piezoelectric coefficient (Sm-PMN-PT), a new design of PENG with a three-dimensional intercalation electrode (IENG) is proposed. By creating many boundary interfaces inside the piezoelectric material, the total amount of surface polarization charges increased, which contributes to an increased current density. The IENG can output a maximum peak shortcircuit current of 320 μA, and the corresponding current density 290 μA cm −2 is 1.93 and 1.61 times the record values of PENG and triboelectric nanogenerator (TENG), respectively. It can also charge a 1 μF capacitor from 0 V to 8 V in 21 cycles, and the equivalent surface charge density 1690 μC m −2 is 1.35 times the record value of TENG.