Multifunctional and Physically Transient Supercapacitors,Triboelectric Nanogenerators,and Capacitive Sensors

Electronic waste (e-waste) grows in parallel with the increasing need for consumer electronics. This, unfortunately, is leading to pollution and massive ecological problems worldwide. A solution to this problem is the use of transient electronics. While transiency of a few components such as transistors and batteries have been proposed already, it is crucial to have all components in electronic devices to be transient. Therefore, the transiency of more electronic components should be demonstrated to alleviate the e-waste problem. Herein, multifunctional nanocomposite electrodes are fabricated using poly(vinyl alcohol), carbon black, and activated carbon. These simple electrodes are then used to fabricate physically transient supercapacitors, triboelectric nanogenerators, and capacitive sensors. Transient supercapacitors are used numerous times with excellent supercapacitive behavior before being discarded, which show promise as an energy storage component for transient systems. The fabricated transient triboelectric nanogenerators are used to harvest mechanical energy, eliminated the need for an external power supply, paving the way to self-powered devices, such as a touchpad as demonstrated herein. The fabricated transient capacitive sensors, on the other hand, have shown long linear sensitivities and offered waste-free monitoring of physiological signals and body motions.     

An Analytical Model of Reactive Diffusion for Transient Electronics

Transient electronics is a class of technology that involves components which physically disappear, in whole or in part, at prescribed rates and at programmed times. Enabled devices include medical monitors that fully resorb when implanted into the human body (“bio‐resorbable”) to avoid long‐term adverse effects, or environmental monitors that dissolve when exposed to water (“eco‐resorbable”) to eliminate the need for collection and recovery. Analytical models for dissolution of the constituent materials represent important design tools for transient electronic systems that are configured to disappear in water or biofluids. Here, solutions for reactive‐diffusion are presented in single‐ and double‐layered structures, in which the remaining thicknesses and electrical resistances are obtained analytically. The dissolution time and rate are defined in terms of the reaction constants and diffusivities of the materials, the thicknesses of the layer, and other properties of materials and solution. These models agree well with the experiments for single layers of Mg and SiO₂, and double layers of Mg/MgO. The underlying physical constants extracted from analysis fall within a broad range previously reported in other studies; these constants can be extremely sensitive to the morphologies of the materials, temperature, and the PH value, concentration, and properties of the surrounding liquid.     

Additive-Free Energetic Film Based on Graphene Oxide and Nanoscale Energetic Coordination Polymer for Transient Microchip

Transient microchips have promising applications in data security and privacy protection. A simple fabrication process and short transient time are two crucial requirements for transient microchips. In this study, a facile drop-casting method is used to develop a transient microchip based on an energetic film and a microheater on a substrate. It is found that the graphene oxide-energetic coordination polymer composite based energetic film plays an important role in simplifying the fabrication process and achieving fast transient time due to its inherent film forming ability, strong binding to substrate, and highly energetic characteristics. The interlayer confinement effect of graphene oxide (GO) can significantly reduce the size of energetic coordination polymer (ECP) to nanometer scale. Van der Waals forces between GO layers and coordination bonds between GO and metal ions are responsible for the film formation ability. Furthermore, the reduction of ECP size and the compact stacking lay the foundation for the excellent combustion and pressure production performance of the energetic film. The strong adhesion of the energetic film and the substrate is confirmed by drop experiments. More importantly, the fabricated silicon based transient microchip can achieve self-destruction within 1 second.     

Dissolvable Metals for Transient Electronics

Reactive dissolution and its effects on electrical conduction, morphological change and chemical transformation in thin films of Mg, AZ31B Mg alloy, Zn, Fe, W, and Mo in de‐ionized (DI) water and simulated body fluids (Hanks’ solution pH 5–8) are systematically studied, to assess the potential for use of these metals in water‐soluble, that is, physically "transient", electronics. The results indicate that the electrical dissolution rates in thin films can be much different that traditionally reported corrosion rates in corresponding bulk materials. Silicon metal oxide field effect transistors (MOSFETs) built with these metals demonstrate feasibility for use in transient electronics.     

Biodegradable Polyanhydrides as Encapsulation Layers for Transient Electronics

Bioresorbable electronic systems represent an emerging class of technology of interest due to their ability to dissolve, chemically degrade, disintegrate, and/or otherwise physically disappear harmlessly in biological environments, as the basis for temporary implants that avoid the need for secondary surgical extraction procedures. Polyanhydride‐based polymers can serve as hydrophobic encapsulation layers for such systems, as a subset of the broader field of transient electronics, where biodegradation eventually occurs by chain scission. Systematic experimental studies that involve immersion in phosphate‐buffered saline solution at various pH values and/or temperatures demonstrate that dissolution occurs through a surface erosion mechanism, with little swelling. The mechanical properties of this polymer are well suited for use in soft, flexible devices, where integration can occur through a mold‐based photopolymerization technique. Studies of the dependence of the polymer properties on monomer compositions and the rates of permeation on coating thicknesses reveal some of the underlying effects. Simple demonstrations illustrate the ability to sustain operation of underlying biodegradable electronic systems for durations between a few hours to a week during complete immersion in aqueous solutions that approximate physiological conditions. Systematic chemical, physical, and in vivo biological studies in animal models reveal no signs of toxicity or other adverse biological responses.     

一种测试半导体制冷器的瞬态方法

ZT值、最大制冷温差和响应时间是表征半导体制冷器性能的重要参数.文中介绍了一种能同时测量这三个参数的瞬态方法,并讨论了热沉对测试结果的影响.利用一个由恒流脉冲发生器和数据采集卡组成的简单测试系统测得制冷器在小电流下的电阻电压和塞贝克电压,通过这两个电压推导出ZT值、最大制冷温差.这种瞬态方法是非接触式测量,准确度高,可用于薄膜热电器件测试;另外瞬态方法耗时短,可大大缩短半导体制冷器可靠性测试的周期.采用这种方法对4mm×4mm×2.4mm的热电制冷器进行实验,环境温度300K时,测得ZT值为0.39,最大温差58.5K,响应时间20s.     

天波超视距雷达瞬态干扰抑制

天波超视距雷达(OTHR)电波通过电离层折射作下视探测,具有观察距离远,观察范围广的特点.但由于采用HF频段,且电波传播环境复杂,不仅海(地)杂波强,而且有很强的干扰,如电台干扰、工业干扰、冲击噪声、闪电冲击和流星余迹回波等.干扰分长时间干扰和瞬态干扰,瞬态干扰持续时间短、强度大.本文首先讨论OTHR接收到的瞬态干扰的特点;然后讨论了瞬态干扰的滤除方法,即采用特征分解方法滤除海杂波,或在频域直接滤除地杂波,检测出瞬态干扰的位置后,在原始信号中挖除存在瞬态干扰的回波点,并用预测内插的方法,消除瞬态干扰谱对目标掩盖作用,使目标特别是舰船目标能被检测出来;最后通过实测数据的检验.     

传输线瞬态响应的一种时域分析方法

提出一种传输线瞬态响应的时域分析方法。该方法对电报方程在时域内差分离散,在建立对空间的一阶微分方程组后,采用精细积分法,可获得传输线瞬态响应。这是一种时域内的半解析数值计算方法,具有方法简单、计算精度高等优点,能够有效地分析具有非线性负载的有损耦合传输线瞬态响应问题,也可以用于输电线路的瞬态分析及故障测距。     

基于PSpice的电力变压器绕组中暂态电压分布的仿真计算

传统对电力变压器绕组中暂态电压分布的仿真计算有多种,但均需编程计算而得,为此提出了一种适用于PSpice仿真的电力变压器绕组中暂态电压分布的电路模型,并对该变压器雷电过电压时的暂态电压分布及正常运行电压分布进行了仿真,结果表明该模型可表达绕组暂态时的表现,且大大简化了计算过程。     

北半球冬季和夏季CALIOP 瞬态响应差异性

利用2008年冬季和夏季星载激光雷达CALIOP版本3一级数据产品,分别对北半球两个季节CALIOP 532 nm垂直通道和平行通道的瞬态响应进行统计分析,对比可知北半球冬季和夏季的瞬态响应具有明显的差异。由于南极大陆和格陵兰岛常年被冰雪覆盖,利用CALIOP在该区域的数据得到532 nm垂直和平行通道的瞬态响应函数作为冰雪后向散射特性,并以此作为判断冰雪的依据。北半球冬季有41.8%的数据点和夏季数据点的特性保持一致,表明这些点未被冰雪覆盖。而其它58.2%的数据点的特性和南极大陆以及格陵兰岛数据点特性一致,表明这些点被冰雪覆盖。     

Boost DC-DC变换器电流滞环暂态控制策略的设计

对数字电流滞环控制Boost DC-DC变换器进行了详细的仿真实验分析,发现暂态过程中存在恢复时间过长和无法完全恢复到目标输出值的问题。针对这一问题,在原有的电流滞环控制策略的基础上提出了一种改进的电流滞环控制方法。具体控制方法是程序自动判断负载电流是否发生突变,以及突变的类型是电流突增或突降。若突增则启动电流突增暂态控制策略,若突降则启动电流突降暂态控制策略,若没有发生突变,则沿用电流滞环稳态控制策略。完成了改进的电流滞环控制方法的详细设计,并进行了仿真和硬件测试。测试结果表明,改进后的控制策略在保持良好的稳态特性基础上明显改善了变换器的暂态特性。与原有的控制策略相比,有效缩短了暂态恢复时间并提高了负载调整率。     

基于峰度特征的瞬态电磁信号检测提取方法

瞬态电磁信号持续时间短,对其进行数据采集和信号处理时,噪声干扰等冗余数据多。利用峰度在表征瞬变、冲击等脉冲信号方面的优势,基于峰度特征和滑动窗技术,研究了噪声干扰下瞬态电磁信号的检测提取方法。分析结果表明,瞬态电磁信号和噪声干扰信号之间的峰度特征值具有较高的区分度,且稳定性好,受信号强度等参数变化的影响小,可用于对单个及多个瞬态电磁信号的检测提取。该方法能有效降低噪声干扰等冗余数据占比,且计算量小、简单便捷,仿真计算和实测结果也验证了该方法的可行性。     

Comparison of the Operation of Polymer/Fullerene,Polymer/Polymer,and Polymer/Nanocrystal Solar Cells: A Transient Photocurrent and Photovoltage Study

We utilize transient techniques to directly compare the operation of polymer/fullerene, polymer/nanocrystal, and polymer/polymer bulk heterojunction solar cells. For all devices, poly(3‐hexylthiophene) (P3HT) is used as the electron donating polymer, in combination with either the fullerene derivative phenyl‐C₆₁‐butyric acid methyl ester (PCBM) in polymer/fullerene cells, CdSe nanoparticles in polymer/nanocrystal cells, or the polyfluorene copolymer poly((9,9‐dioctylfluorene)‐2,7‐diyl‐alt‐[4,7‐bis(3‐hexylthien‐5‐yl)‐2,1,3‐benzothiadiazole]‐2,2‐diyl) (F8TBT) in polymer/polymer cells. Transient photocurrent and photovoltage measurements are used to probe the dynamics of charge‐separated carriers, with vastly different dynamic behavior observed for polymer/fullerene, polymer/polymer, and polymer/nanocrystal devices on the microsecond to millisecond timescale. Furthermore, by employing transient photocurrent analysis with different applied voltages we are also able to probe the dynamics behavior of these cells from short circuit to open circuit. P3HT/F8TBT and P3HT/CdSe devices are characterized by poor charge extraction of the long‐lived carriers attributed to charge trapping. P3HT/PCBM devices, in contrast, show relatively trap‐free operation with the variation in the photocurrent decay kinetics with applied bias at low intensity, consistent with the drift of free charges under a uniform electric field. Under solar conditions at the maximum power point, we see direct evidence of bimolecular recombination in the P3HT/PCBM device competing with charge extraction. Transient photovoltage measurements reveal that, at open circuit, photogenerated charges have similar lifetimes in all device types, and hence, the extraction of these long‐lived charges is a limiting process in polymer/nanocrystal and polymer/polymer devices.     

端接非线性负载的非均匀传输线瞬态分析

在均匀多导体传输线的时域有限差分法(FDTD)基础上，对非均匀多导体传输线及端接非线性负载的情况进行了分析。结果表明：对于非均匀多导体传输线，采用FDTD法进行瞬态分析极为方便，并且可以处理端接非线性负载的情况；同时，还可获得线上各点的电压、电流波过程。通过实例验证了所提出的FDTD算法的有效性，可用于传输线波过程的研究。     

非晶硅薄膜瞬态光电导的光致变化

研究了非晶硅薄膜的瞬态光电导的光致变化情况.用通常的非晶态半导体的瞬态光电流的乘方规律和稳态光电导的扩展指数规律都不能对试验数据进行很好的拟合,而采用两个指数函数相加的形式可以对实验数据进行很好的拟合.这表明非晶硅薄膜长时间的衰退不是由带尾态决定,而是由深的陷阱决定的.两个指数函数的衰退分别对应于距导带0.52eV和0.59eV的两个陷阱,这两个陷阱可以被指认为带隙中的荷负电中心.光照后,带隙中的复合中心增加,导致电子寿命的减少,从而引起光电导的衰退.     

非晶硅薄膜瞬态光电导的光致变化

研究了非晶硅薄膜的瞬态光电导的光致变化情况.用通常的非晶态半导体的瞬态光电流的乘方规律和稳态光电导的扩展指数规律都不能对试验数据进行很好的拟合,而采用两个指数函数相加的形式可以对实验数据进行很好的拟合.这表明非晶硅薄膜长时间的衰退不是由带尾态决定,而是由深的陷阱决定的.两个指数函数的衰退分别对应于距导带0.52eV和0.59eV的两个陷阱,这两个陷阱可以被指认为带隙中的荷负电中心.光照后,带隙中的复合中心增加,导致电子寿命的减少,从而引起光电导的衰退.     

Biodegradable Thin Metal Foils and Spin‐On Glass Materials for Transient Electronics

Biodegradable substrates and encapsulating materials play critical roles in the development of an emerging class of semiconductor technology, generally referred as “transient electronics”, whose key characteristic is an ability to dissolve completely, in a controlled manner, upon immersion in ground water or biofluids. The results presented here introduce the use of thin foils of Mo, Fe, W, or Zn as biodegradable substrates and silicate spin‐on‐glass (SOG) materials as insulating and encapsulating layers, with demonstrations of transient active (diode and transistor) and passive (capacitor and inductor) electronic components. Complete measurements of electrical characteristics demonstrate that the device performance can reach levels comparable to those possible with conventional, nontransient materials. Dissolution kinetics of the foils and cytotoxicity tests of the SOG yield information relevant to use in transient electronics for temporary biomedical implants, resorbable environmental monitors, and reduced waste consumer electronics.     

脉冲方波驱动强化热电制冷的瞬态特性

采用有限差分法对脉冲电压驱动下的瞬态热电效应及其动态特性过程进行了理论分析,探索了非稳态工况下帕尔帖效应、焦耳热效应与傅里叶导热效应之间的耦合关系及其关键制约因素对制冷性能的影响规律,进而探讨了脉冲驱动强化热电制冷性能的作用机理。分析结果得到,在合理电压域值内采用主动控制方法,对热电模块周期性施加数倍于稳态工况理想电压的脉冲突变电压,有益于充分利用帕尔贴制冷效应而推迟出现以焦耳热和傅里叶热耗散形式为主的内部热积聚对热电模块冷端引起的负效应,并能瞬态实现冷端面的制冷强化作用和最大程度实现输入电能的有效转换。该结论不仅为进一步提出脉冲驱动模式的优化控制策略提供了理论依据,也为瞬态热电制冷效应的应用开辟了一条新思路。     

In-situ analysis of thermal properties of polymer composites by embedded LED temperature sensor

Real time and accurate measurement of thermal conductivity of polymer composites with thermal conductive fillers challenges researchers in industrial application. Here, we present an in-situ measurement approach by embedding a LED or diode as a combined heat source and temperature sensor into the filled polymer and using the well-established transient measuring method based on forward voltage variation to determine the temperature response of the sensor in polymer. Numerical model fitting is applied to estimate the thermal conductivity of the polymer composites with different filler/polymer ratios. These findings are compared with other thermal conductivity test methods such as the laser flash method and the Modular Differential Scanning Calorimeter (MDSC). The proposed approach provides a quick way of measuring the thermal conductivity in relatively thin polymer composites and agrees well with the MDSC method. Another advantage is that it can work with the real samples made for the application in mind, so its results can be used directly.     

Evaluation of short pulse and short time thermal transient measurements

Thermal transient recording and the time constant spectrum analysis are widely used methods in the thermal testing and qualification of IC packages. A limitation of these methods is that recording of the complete transient response requires long time. This limitation, however, can be overcome by sophisticated procedures. The first method is to apply short power pulse for excitation; the second one is the interruption of the transients long before the thermal equilibrium is reached. The paper offers algorithms to evaluate these short pulse and short time measurements. The presented methods are suitable if the extraction of the little time constants is needed. This is the case if the transient method is used e.g. for die attach quality checking.