Zongming Su

Self-Powered Analogue Smart Skin

The progress of smart skin technology presents unprecedented opportunities for artificial intelligence. Resolution enhancement and energy conservation are critical to improve the perception and standby time of robots. Here, we present a self-powered analogue smart skin for detecting contact location and velocity of the object, based on a single-electrode contact electrification effect and planar electrostatic induction. Using an analogue localizing method, the resolution of this two-dimensional smart skin can be achieved at 1.9 mm with only four terminals, which notably decreases the terminal number of smart skins. The sensitivity of this smart skin is remarkable, which can even perceive the perturbation of a honey bee. Meanwhile, benefiting from the triboelectric mechanism, extra power supply is unnecessary for this smart skin. Therefore, it solves the problems of batteries and connecting wires for smart skins. With microstructured poly(dimethylsiloxane) films and silver nanowire electrodes, it can be covered on the skin with transparency, flexibility, and high sensitivity.

Single-Step Fluorocarbon Plasma Treatment-Induced Wrinkle Structure for High-Performance Triboelectric Nanogenerator.

A triboelectric nanogenerator (TENG) has been thought to be a promising method to harvest energy from environment. To date, the utilization of surface structure and material modification has been considered the most effective way to increase its performance. In this work, a wrinkle structure based high-performance TENG is presented. Using the fluorocarbon plasma treatment method, material modification and surface structure are introduced in one step. The output ability of TENG is dramatically enhanced. After the optimization of plasma treatment, the maximum current and surface charge density are 182 μA about 165 μC m(-2). Compared with untreated TENG, the wrinkle structure makes the current and surface charge density increase by 810% and 528%, separately. X-ray photoelectron spectroscopy is employed to analyze the chemical modification mechanism of this fluorocarbon plasma treatment. Facilitated by its high output performance, this device could directly light 76 blue light emitting diodes under finger typing. The output electric energy could be stored then utilized to power a commercial calculator. As a result of the simple fabrication process and high output ability, devices fabricated using this method could bring forward practical applications using TENGs as power sources.

Integrated self-charging power unit with flexible supercapacitor and triboelectric nanogenerator

With the rapid development of wearable devices and portable electronics, highly efficient and stable self-powered systems are in great demand. However, most harvesting and storage devices of such systems are separate units, which reduce the power density and limit their applications. In this work, we implemented an integrated sandwich-shaped, self-charging power unit (SCPU) with a wrinkled PDMS-based triboelectric nanogenerator and CNT/paper-based solid-state supercapacitor. During ambient vibration process, this SCPU could simultaneously harvest and store energy, efficiently converting mechanical energy into electrochemical energy. The self-charging capability of this SCPU is demonstrated by periodic compressive stress, charging 900 mV within 3 h. Additionally, using three serially connected SCPUs as power supply, it could drive a commercial calculator working continuously and an electrochromic device as a smart window during the coloration and bleaching processes. Considering its efficient structure and facile fabrication, this novel integrated SCPU provides a feasible solution for sustainable power supply and shows great potential in micro-energy fields and self-powered systems.

Electrification based devices with encapsulated liquid for energy harvesting, multifunctional sensing, and self-powered visualized detection

Electrification between a solid and a liquid is a common but complex phenomenon which can both benefit and cause problems for industry, the laboratory, and our daily life. Here, utilizing this phenomenon, we designed a multifunctional device which can harvest vibration energy, sense mechanical/chemical changes, and intuitively detect wobble/leakage of liquid. Under low frequency, the device can generate room mean square voltages higher than 10 V and an average power of 0.9 μW, which is a great enhancement compared to previous liquid involved devices. Moreover, the device was demonstrated as a multifunctional active mechanical/chemical sensor for detecting the rotation and in situ measuring concentration in a specific range, and it has high stability due to the encapsulated environment. Finally, the device was utilized as a self-powered visualized system for detecting the wobble/leakage of the encapsulated liquid using itself as the energy source, which not only simplifies the measurement process, but also makes the total system power-free.

Highly Compressible Integrated Supercapacitor–Piezoresistance-Sensor System with CNT–PDMS Sponge for Health Monitoring

Rapid improvement of wearable electronics stimulates the demands for the matched functional devices and energy storage devices. Meanwhile, wearable microsystem requires every parts possessing high compressibility to accommodate large-scale mechanical deformations and complex conditions. In this work, a general carbon nanotube-polydimethylsiloxane (CNT-PDMS) sponge electrode is fabricated as the elementary component of the compressible system. CNT-PDMS sponge performs high sensitivity as a piezoresistance sensor, which is capable of detecting stress repeatedly and owns great electrochemical performance as a compressible supercapacitor which maintains stably under compressive strains, respectively. Assembled with the piezoresistance sensor and the compressible supercapacitor, such highly compressible integrated system can power and modulate the low-power electronic devices reliably. More importantly, attached to the epidermal skin or clothes, it can detect human motions, ranging from speech recognition to breathing record, thus showing feasibility in real-time health monitor and human-machine interfaces.

All-fabric-based wearable self-charging power cloth

We present an all-fabric-based self-charging power cloth (SCPC), which integrates a fabric-based single-electrode triboelectric generator (STEG) and a flexible supercapacitor. To effectively scavenge mechanical energy from the human motion, the STEG could be directly woven among the cloth, exhibiting excellent output capability. Meanwhile, taking advantage of fabric structures with a large surface-area and carbon nanotubes with high conductivity, the wearable supercapacitor exhibits high areal capacitance (16.76 mF/cm2) and stable cycling performance. With the fabric configuration and the aim of simultaneously collecting body motion energy by STEG and storing in supercapacitors, such SCPC could be easily integrated with textiles and charged to nearly 100 mV during the running motion within 6 min, showing great potential in self-powered wearable electronics and smart cloths.

High performance triboelectric nanogenerators with aligned carbon nanotubes

As the essential element of a triboelectric nanogenerator (TENG), friction layers play key roles that determine the device performance, which can be enhanced by material selection and surface modification. In this work, we have embedded aligned carbon nanotubes (CNTs) on the polydimethylsiloxane (PDMS) surface as the effective dielectric layer to donate electrons. This layer not only increases the electron generation for the output, but also shows notable stretchability. The length and the properties of the aligned CNTs can be controlled precisely. Using the 40 μm CNT as an example, the fabricated CNT-PDMS TENG shows an output voltage of 150 V and a current density of 60 mA m-2, which are 250% and 300% enhancement compared to the TENG using directly doped PDMS/multiwall carbon nanotubes, respectively. The maximum power density of this TENG reaches 4.62 W m-2 at an external load of 30 MΩ. The TENG has demonstrated superior stability during cyclic measurement of over 12 000 cycles. Besides, the aligned CNT-PDMS film shows superhydrophobicity (154°) and good sheet resistance of 280 Ω sq-1. This stretchable aligned CNT-PDMS film can be universally utilized as a positive triboelectric layer pairing with polymeric materials such as polyethylene terephthalate, polyimide, PDMS and polytetrafluoroethylene for TENGs. This work provides an effective method of structure design for flexible and stretchable nanogenerators.

Controlled fabrication of nanoscale wrinkle structure by fluorocarbon plasma for highly transparent triboelectric nanogenerator

In this paper, we report a novel nanoscale wrinkle-structure fabrication process using fluorocarbon plasma on poly(dimethylsiloxane) (PDMS) and Solaris membranes. Wrinkles with wavelengths of hundreds of nanometers were obtained on these two materials, showing that the fabrication process was universally applicable. By varying the plasma-treating time, the wavelength of the wrinkle structure could be controlled. Highly transparent membranes with wrinkle patterns were obtained when the plasma-treating time was <125 s. The transmittances of these membranes were >90% in the visible region, making it difficult to distinguish them from a flat membrane. The deposited fluorocarbon polymer also dramatically reduced the surface energy, which allowed us to replicate the wrinkle pattern with high precision onto other membranes without any surfactant coating. The combined advantages of high electron affinity and high transparency enabled the fabricated membrane to improve the performance of a triboelectric nanogenerator. This nanoscale, single-step, and universal wrinkle-pattern fabrication process, with the functionality of high transparency and ultra-low surface energy, shows an attractive potential for future applications in micro- and nanodevices, especially in transparent energy harvesters.

A single-electrode wearable triboelectric nanogenerator based on conductive & stretchable fabric

This paper reports a wearable triboelectric nanogenerator (TENG) based on the conductive and stretchable composite fabric, which is cost-effective and can be easily mass produced. Multi-wall carbon nanotubes (MWCNT) are directly composited with the cotton knitting fabric through dipping and drying method. The sheet resistance reduces to 505 Ω/sq after 10 cycles. Using this single knitting fabric electrode, the peak output power density of the TENG achieves ~12 μW/cm2.

Waterproof and stretchable triboelectric nanogenerator for biomechanical energy harvesting and self-powered sensing

We introduce a waterproof and stretchable triboelectric nanogenerator (TENG) that can be attached on the human body, such as fingers and the wrist, to harvest mechanical energy from body movement. The whole device is composed of stretchable material, making it able to endure diverse mechanical deformations and scavenge energy from them. Under gentle mechanical motions of pressing, stretching and bending, the device with an effective area of 1  × 2 cm2 can generate the peak-to-peak output current of 257.5 nA, 50.2 nA, and 33.5 nA, respectively. Besides, the TENG is tightly encapsulated, enabling it to avoid the influence of the external environment like humidity changes and harvest energy under water. Particularly, owing to the thin and soft properties of the encapsulation film, the device can respond to weak vibrations like the wrist pulse and act as a self-powered pulse sensor, which broadens its application prospects in the field of wearable energy harvesting devices and self-powered sensing systems.