Flexible inorganic bioelectronics represent a newly emerging and rapid developing research area.With its great power in enhancing the acquisition,management and utilization of health information,it is expected that these flexible and stretchable devices could underlie the new solutions to human health problems.Recent advances in this area including materials,devices,integrated systems and their biomedical applications indicate that through conformal and seamless contact with human body,the measurement becomes continuous and convenient with yields of higher quality data.This review covers recent progresses in flexible inorganic bio-electronics for human physiological parameters’monitoring in a wearable and continuous way.Strategies including materials,structures and device design are introduced with highlights toward the ability to solve remaining challenges in the measurement process.Advances in measuring bioelectrical signals,i.e.,the electrophysiological signals(including EEG,ECoG,ECG,and EMG),biophysical signals(including body temperature,strain,pressure,and acoustic signals)and biochemical signals(including sweat,glucose,and interstitial fluid)have been summarized.In the end,given the application property of this topic,the future research directions are outlooked.
As rapid development in wearable/implantable electronic devices benefit human life in daily health monitoring and disease treatment medically, all kinds of flexible and/or stretchable electronic devices are booming, together with which is the demanding of energy supply with similar mechanical property. Due to its ability in converting mechanical energy lying in human body into electric energy, energy harvesters based on piezoelectric materials are promising for applications in wearable/implantable device's energy supply in a renewable, clean and life-long way. Here the mechanics of traditional piezoelectrics in energy harvesting is reviewed, including why piezoelectricity is the choice for minor energy harvesting to power the implantable/wearable electronics and how. Different kinds of up to date flexible piezoelectric devices for energy harvesting are introduced, such as nanogenerators based on Zn O and thin and conformal energy harvester based on PZT. A detailed theoretical model of the flexible thin film energy harvester based on PZT nanoribbons is summarized, together with the in vivo demonstration of energy harvesting by integrating it with swine heart. Then the initial researches on stretchable energy harvesters based on piezoelectric material in wavy or serpentine configuration are introduced as well.
Ceramics used in the high temperature environment are inevitably subjected to sudden temperature change, which may lead to catastrophic thermal shock failure due to the intrinsic brittleness of ceramics. In this paper, an experimental platform is designed to realize the in-situ observation during the thermal shock experiments. Experimental results show that all the cracks initiate from one of the edge midpoints and propagate to another one for square specimens. Such experimental observation is consistent with the maximum tensile stress zone with the maximum temperature gradient given by the finite element method(FEM). The different crack modes resulting from different heating rates after thermal shock experiments are observed and analyzed. Comparison between different clamping methods is conducted to study the effects of boundary conditions on the thermal shock experiments. Furthermore, in order to improve the thermal shock performance of alumina ceramics, crack arrest blocks are added near the edge midpoint. The thickness, shape and arrangement of the blocks are systematically investigated to understand the mechanism of improvement of thermal shock resistance.
