Han Ouyang

Biodegradable triboelectric nanogenerator as a life-time designed implantable power source

Mechanical energy in vivo could be harvested by BD-TENG in a designed time frame. Transient electronics built with degradable organic and inorganic materials is an emerging area and has shown great potential for in vivo sensors and therapeutic devices. However, most of these devices require external power sources to function, which may limit their applications for in vivo cases. We report a biodegradable triboelectric nanogenerator (BD-TENG) for in vivo biomechanical energy harvesting, which can be degraded and resorbed in an animal body after completing its work cycle without any adverse long-term effects. Tunable electrical output capabilities and degradation features were achieved by fabricated BD-TENG using different materials. When applying BD-TENG to power two complementary micrograting electrodes, a DC-pulsed electrical field was generated, and the nerve cell growth was successfully orientated, showing its feasibility for neuron-repairing process. Our work demonstrates the potential of BD-TENG as a power source for transient medical devices.

Self‐Powered Pulse Sensor for Antidiastole of Cardiovascular Disease

Cardiovascular diseases are the leading cause of death globally; fortunately, 90% of cardiovascular diseases are preventable by long-term monitoring of physiological signals. Stable, ultralow power consumption, and high-sensitivity sensors are significant for miniaturized wearable physiological signal monitoring systems. Here, this study proposes a flexible self-powered ultrasensitive pulse sensor (SUPS) based on triboelectric active sensor with excellent output performance (1.52 V), high peak signal-noise ratio (45 dB), long-term performance (107 cycles), and low cost price. Attributed to the crucial features of acquiring easy-processed pulse waveform, which is consistent with second derivative of signal from conventional pulse sensor, SUPS can be integrated with a bluetooth chip to provide accurate, wireless, and real-time monitoring of pulse signals of cardiovascular system on a smart phone/PC. Antidiastole of coronary heart disease, atrial septal defect, and atrial fibrillation are made, and the arrhythmia (atrial fibrillation) is indicative diagnosed from health, by characteristic exponent analysis of pulse signals accessed from volunteer patients. This SUPS is expected to be applied in self-powered, wearable intelligent mobile diagnosis of cardiovascular disease in the future.

Robust Multilayered Encapsulation for High-Performance Triboelectric Nanogenerator in Harsh Environment

Harvesting biomechanical energy especially in vivo is of special significance for sustainable powering of wearable/implantable electronics. The triboelectric nanogenerator (TENG) is one of the most promising solutions considering its high efficiency, low cost, light weight, and easy fabrication, but its performance will be greatly affected if there is moisture or liquid leaked into the device when applied in vivo. Here, we demonstrate a multiple encapsulation process of the TENG to maintain its output performance in various harsh environments. Through systematic studies, the encapsulated TENG showed great reliability in humid or even harsh environment over 30 days with a stability index of more than 95%. Given its outstanding reliability, the TENG has the potential to be applied in variety of circumstances to function as a sustainable power source for self-powered biomedical electronics and environmental sensing systems.

Thermo-Driven Evaporation Self-Assembly and Dynamic Analysis of Homocentric Carbon Nanotube Rings

MWCNTs self-assemble into various homocentric rings in a thermo-driven self-assembly system. Closely packed and scatteredly packed MWCNT rings self-assemble on a Si-SiO2 substrate, whereas on a Au substrate smoothly packed MWCNT rings, rings with waviness, and rings with shuttle-like holes are seen to self-assemble. The dynamic self-assembly process includes convection flow and swirling flow.

The modulation effect of the convexity of silicon topological nanostructures on the growth of mesenchymal stem cells

A series of different topological nanostructures are fabricated on silicon wafer using metal-assisted chemical etching. The modulation effect of these nanostructures on the size, filopodia generation and growth orientation of the rat mesenchymal stem cells (MSCs) are studied. These topological nanostructures tend to induce the MSCs to have smaller size, but they generate much more filopodia compared to the flat silicon control. The modulation effects of these nanostructures are dependent on their surface convexity, as analysed by grey-level value histogram and fast Fourier transformation (FFT). A surface with a higher portion of convex area is better at supporting larger cell sizes. The wavenumber analysis by FFT further determines its effect on filopodia generation. In addition, the growth orientation of the cells are also guided by the surface convexity. On the porous and spongy surface, the cell filopodia extend and grow in avoidance of large sinking pits. On the columnar and spiny surface, the cell body and filopodia extend only on the tips of these nanostructures. Our study reveals that surface convexity is an important factor modulating cell behavior, and convexity analysis by image processing can work as a fast and simple evaluation standard to design topological nanostructures.