物理学Physics

Suppressed thermal transport in silicon nanoribbons by inhomogeneous strain

非匀称应变按捺硅纳米带中的热输运

▲ 作者：Lin Yang, Shengying Yue, Yi Tao, Shuo Qiao, Hang Li, Zhaohe Dai, Bai Song, Yunfei Chen, Jinlong Du, Deyu Li Peng Gao

▲ 链接：

https://www.nature.com/articles/s41586-024-07390-4

▲ 择要：

纳米级布局可以孕育发生极度应变，从而实现史无前例的质料特征，例如定制电子带隙，提崇高高贵导温度以及加强的电催化活性。虽然已经知匀称应变对于热流的影响有限，但因为界面以及缺陷的共存，非匀称应变的影响仍旧难以捉摸。

研究者经由过程于定制的微器件上弯曲单个硅纳米带引入非匀称应变，并丈量其对于热输运的影响，同时以亚纳米分辩率表征应变相干的振动谱，从而解决了这一空缺。

研究成果注解，每一纳米0.112%的应变梯度可以致使热导率急剧降落34 5%，与匀称应变下丈量的险些恒定值造成光鲜对于比。研究者进一步哄骗电子能量丧失谱绘制下场部晶格振动谱，这展现了声子沿应变梯度的峰值位移为数百万电子伏特。

第一性道理计较证实，这类怪异的声子谱展宽效应加强了声子散射，极年夜地拦阻了热输运。研究展现了持久存于的非匀称应变下晶格动力学难题的一个要害部门，这于匀称应变下是不存于的，而且凌驾了传统的理解。

▲ Abstract：

Nanoscale structures can produce extreme strain that enables unprecedented material properties, such as tailored electronic bandgap, elevated superconducting temperature and enhanced electrocatalytic activity. While uniform strains are known to elicit limited effects on heat flow, the impact of inhomogeneous strains has remained elusive owing to the coexistence of interfaces and defects. Here we address this gap by introducing inhomogeneous strain through bending individual silicon nanoribbons on a custom-fabricated microdevice and measuring its effect on thermal transport while characterizing the strain-dependent vibrational spectra with sub-nanometre resolution. Our results show that a strain gradient of 0.112% per nanometre could lead to a drastic thermal conductivity reduction of 34? ?5%, in clear contrast to the nearly constant values measured under uniform strains. We further map the local lattice vibrational spectra using electron energy-loss spectroscopy, which reveals phonon peak shifts of several millielectron-volts along the strain gradient. This unique phonon spectra broadening effect intensifies phonon scattering and substantially impedes thermal transport, as evidenced by first-principles calculations. Our work uncovers a crucial piece of the long-standing puzzle of lattice dynamics under inhomogeneous strain, which is absent under uniform strain and eludes conventional understanding.

Self-oscillating polymeric refrigerator with high energy efficiency

高能效自振荡聚合物制冷机

▲ 作者：Donglin Han, Yingjing Zhang, Cenling Huang, Shanyu Zheng, Dongyuan Wu, Qiang Li, Feihong Du, Hongxiao Duan, Weilin Chen, Junye Shi, Jiangping Chen, Gang Liu, Xin Chen Xiaoshi Qian

▲ 链接：

https://www.nature.com/articles/s41586-024-07375-3

▲ 择要：

介电质料中同时存于着电热以及电致伸缩效应。联合这两种效果可以实现轻量化，紧凑的局部热治理，这是由电热制冷所承诺的。只管有一些数值模子以及示用意，今朝的电热冰箱仍旧依靠在外部附件来驱开工作体，是以致使装备级冷却功率密度以及机能系数（COP）较低。

研究者陈诉了一种哄骗聚合铁电体提供的电热机械协同作用的电热薄膜装配。于一次交流电刺激下，该装配由事情体自身举行热轮回以及机械轮回，造成无外部驱动、自轮回的软冰箱。

该原型提供了间接丈量的冷却功率密度为6.5 W g-1，于零温度规模下的峰值COP跨越58。该器件仅为30微米厚的聚合物薄膜，于开放情况中，于4K的温度规模内实现了靠近24的COP（32%的热力学效率）。

与被动冷却比拟，薄膜冰箱可以当即对于电子芯片孕育发生17.5 K的分外温度降落。柔软的聚合物冰箱可以感知、驱动以及泵送热量，以提供主动的局部热治理。

▲ Abstract：

Electrocaloric and electrostrictive effects concurrently exist in dielectric materials. Combining these two effects could achieve the lightweight, compact localized thermal management that is promised by electrocaloric refrigeration. Despite a handful of numerical models and schematic presentations current electrocaloric refrigerators still rely on external accessories to drive the working bodies and hence result in a low device-level cooling power density and coefficient of performance (COP). Here we report an electrocaloric thin-film device that uses the electro-thermomechanical synergy provided by polymeric ferroelectrics. Under one-time a.c. electric stimulation, the device is thermally and mechanically cycled by the working body itself, resulting in an external-driver-free, self-cycling, soft refrigerator. The prototype offers a directly measured cooling power density of 6.5 W g-1 and a peak COP exceeding 58 under a zero temperature span. Being merely a 30- m-thick polymer film, the device achieved a COP close to 24 under a 4 K temperature span in an open ambient environment (32% thermodynamic efficiency). Compared with passive cooling, the thin-film refrigerator could i妹妹ediately induce an additional 17.5?K temperature drop against an electronic chip. The soft, polymeric refrigerator can sense, actuate and pump heat to provide automatic localized thermal management.

Strain-invariant stretchable radio-frequency electronics

应变稳定可拉伸射频电子学

▲ 作者：Sun Hong Kim, Abdul Basir, Raudel Avila, Jaeman Lim, Seong Woo Hong, Geonoh Choe, Joo Hwan Shin, Jin Hee Hwang, Sun Young Park, Jiho Joo, Chanmi Lee, Jaehoon Choi, Byunghun Lee, Kwang-Seong Choi, Sungmook Jung, Tae-il Kim, Hyoungsuk Yoo Yei Hwan Jung

▲ 链接：

https://www.nature.com/articles/s41586-024-07383-3

▲ 择要：

无线模块经由过程射频（RF）电子器件提供通讯以及能量网络功效，是皮肤界面可拉伸电子器件的主要构成部门。然而，近来对于可拉伸射频元件的研究注解，纵然于相对于较低的弹性应变下，电机能也会发生本色性变迁，例如天线谐振频次的移位。

这类变迁间接致使可拉伸体系中的无线旌旗灯号强度或者功率传输效率年夜年夜降低，出格是于诸如皮肤外貌的物理动态情况中。研究者提出了应变稳定的可拉伸射频电子元件，可以或许于各类弹性应变下彻底连结原始射频特征，使用 介电弹性 质料作为衬底。

介电弹性质料具备物理可调谐的介电特征，可有用地防止射频电子接口中孕育发生的频移。与传统的可拉伸基板质料比拟，这类质料具备优胜的电气、机械以及热机能，合用在高机能可拉伸射频电子装备。

研究者描写了质料、打造以及设计计谋，这些计谋是基在试验以及计较研究实现要害射频元件应变稳定举动的根蒂根基。末了，作者提出了一套基在应变稳定可拉伸射频电子器件的皮肤接口无线医疗监督器，其于应变下的无线操作间隔可达30米。

▲ Abstract：

Wireless modules that provide teleco妹妹unications and power-harvesting capabilities enabled by radio-frequency (RF) electronics are vital components of skin-interfaced stretchable electronics. However, recent studies on stretchable RF components have demonstrated that substantial changes in electrical properties, such as a shift in the antenna resonance frequency, occur even under relatively low elastic strains. Such changes lead directly to greatly reduced wireless signal strength or power-transfer efficiency in stretchable systems, particularly in physically dynamic environments such as the surface of the skin. Here we present strain-invariant stretchable RF electronics capable of completely maintaining the original RF properties under various elastic strains using a dielectro-elastic material as the substrate. Dielectro-elastic materials have physically tunable dielectric properties that effectively avert frequency shifts arising in interfacing RF electronics. Compared with conventional stretchable substrate materials, our material has superior electrical, mechanical and thermal properties that are suitable for high-performance stretchable RF electronics. In this paper, we describe the materials, fabrication and design strategies that serve as the foundation for enabling the strain-invariant behaviour of key RF components based on experimental and computational studies. Finally, we present a set of skin-interfaced wireless healthcare monitors based on strain-invariant stretchable RF electronics with a wireless operational distance of up to 30?m under strain.

电子信息学Electronic informatics

A vision chip with complementary pathways for open-world sensing

具备开放世界传感互补路径的视觉芯片

▲ 作者：Zheyu Yang, Taoyi Wang, Yihan Lin, Yuguo Chen, Hui Zeng, Jing Pei, Jiazheng Wang, Xue Liu, Yichun Zhou, Jianqiang Zhang, Xin Wang, Xinhao Lv, Rong Zhao Luping Shi

▲ 链接：

https://www.nature.com/articles/s41586-024-07358-4

▲ 择要：

于开放世界运用中，图象传感器于处置惩罚动态、多样化以及不成猜测的场景时面对着伟大的应战。然而，图象传感器向高速、高分辩率、年夜动态规模以及高精度标的目的成长遭到功率以及带宽的限定。

研究者提出了一种受人类视觉体系开导的互补感知范式，该范式触及将视觉信息剖析为基在原语的暗示，并将这些原语组合成两条互补的视觉路径：用在正确认知的以认知为导向的路径以及用在倏地反映的以步履为导向的路径。

为实现这一范式，研究者开发了一种名为 天眸芯 的视觉芯片，该芯片联合了混淆像素阵列以及并行异构读出架构。哄骗互补视觉路径的特征，天眼实现了高达10,000 fps的高速传感，130 dB的动态规模，于空间分辩率，速率以及动态规模方面都是进步前辈的数字。

此外，它自顺应地削减了90%的带宽。他们展示了将天眸芯集成到主动驾驶体系中的威力，纵然于开放门路上具备应战性的角落环境下，也能实现正确、倏地以及强盛的感知。基在原始的互补传感范式有助在降服开发用在各类开放世界运用的视觉体系的基本限定。

▲ Abstract：

Image sensors face substantial challenges when dealing with dynamic, diverse and unpredictable scenes in open-world applications. However, the development of image sensors towards high speed, high resolution, large dynamic range and high precision is limited by power and bandwidth. Here we present a complementary sensing paradigm inspired by the human visual system that involves parsing visual information into primitive-based representations and assembling these primitives to form two complementary vision pathways: a cognition-oriented pathway for accurate cognition and an action-oriented pathway for rapid response. To realize this paradigm, a vision chip called Tianmouc is developed, incorporating a hybrid pixel array and a parallel-and-heterogeneous readout architecture. Leveraging the characteristics of the complementary vision pathway, Tianmouc achieves high-speed sensing of up to 10,000?fps, a dynamic range of 130?dB and an advanced figure of merit in terms of spatial resolution, speed and dynamic range. Furthermore, it adaptively reduces bandwidth by 90%. We demonstrate the integration of a Tianmouc chip into an autonomous driving system, showcasing its abilities to enable accurate, fast and robust perception, even in challenging corner cases on open roads. The primitive-based complementary sensing paradigm helps in overcoming fundamental limitations in developing vision systems for diverse open-world applications.

Low-latency automotive vision with event cameras

带有事务摄像头的低延迟汽车视觉

▲ 作者：Daniel Gehrig Davide Scaramuzza

▲ 链接：

https://www.nature.com/articles/s41586-024-07409-w

▲ 择要：

今朝，高级驾驶辅助体系中使用的计较机视觉算法依靠在基在图象的RGB摄像头，为了提供保险的驾驶体验，带宽延迟是一个要害的衡量。为相识决这个问题，事务摄像机已经经成为另外一种视觉传感器。

事务相机异步丈量强度的变迁，提供高时间分辩率以及稀少性，显著降低带宽以及延迟要求。只管有这些长处，基在事务相机的算法要末效率很高，但于正确性方面掉队在基在图象的算法，要末捐躯事务的稀少性以及效率来得到近似的成果。

为了降服这个问题，研究者提出了一种基在事务以及帧的混淆对于象检测器，它保留了每一种模式的长处，是以不会遭到这类衡量的影响。该要领哄骗事务的高时间分辩率以及稀少性和尺度图象中富厚但低时间分辩率的信息来天生高效，高速度的方针检测，削减感知以及计较延迟。

研究注解，使用每一秒20帧的RGB相机加之事务相机可以实现与每一秒45帧相机带宽的5000帧相机不异的延迟，而不会影响精度。该要领经由过程展现事务相机的潜力，为于边沿环境下实现高效以及稳健的感知摊平了门路。

▲ Abstract：

The computer vision algorithms used currently in advanced driver assistance systems rely on image-based RGB cameras, leading to a critical bandwidth latency trade-off for delivering safe driving experiences. To address this, event cameras have emerged as alternative vision sensors. Event cameras measure the changes in intensity asynchronously, offering high temporal resolution and sparsity, markedly reducing bandwidth and latency requirements1. Despite these advantages, event-camera-based algorithms are either highly efficient but lag behind image-based ones in terms of accuracy or sacrifice the sparsity and efficiency of events to achieve comparable results. To overcome this, here we propose a hybrid event- and frame-based object detector that preserves the advantages of each modality and thus does not suffer from this trade-off. Our method exploits the high temporal resolution and sparsity of events and the rich but low temporal resolution information in standard images to generate efficient, high-rate object detections, reducing perceptual and computational latency. We show that the use of a 20 frames per second (fps) RGB camera plus an event camera can achieve the same latency as a 5,000-fps camera with the bandwidth of a 45-fps camera without compromising accuracy. Our approach paves the way for efficient and robust perception in edge-case scenarios by uncovering the potential of event cameras.

能源Energy

Electric recycling of Portland cement at scale

年夜范围水泥电收受接管

▲ 作者：Cyrille F. Dunant, Shiju Joseph, Rohit Prajapati Julian M. Allwood

▲ 链接：

https://www.nature.com/articles/s41586-024-07338-8

▲ 择要：

水泥出产形成了全世界7.5%的报酬二氧化碳排放，这是由石���灰石脱碳以及化石燃料燃烧惹起的。今朝的脱碳计谋包孕用增补质料代替波特兰熟料，但这些重要呈现于排放历程中，开发替换粘合剂但还没有到达范围，或者者接纳仍旧开释一些排放的碳捕捉以及贮存。

然而，用过的水泥是一种潜于的富厚的脱碳原料。作者研究注解，收受接管的水泥浆可以再熟化，假如作为部门替换石灰白云石助熔剂用在今朝的钢铁收受接管。所患上矿渣满意现有硅酸盐熟料的要求，可与煅烧黏土以及石灰石有用混淆。

该工艺对于收受接管的水泥膏体的二氧化硅含量和可能来自废物的二氧化硅以及氧化铝含量很敏感，但这可以很轻易地调解。研究注解，拟议的工艺可能具备经济竞争力，假如由无排放的电力供电，可以实现零排放水泥，同时还可以经由过程削减石灰助熔剂需求来削减钢铁收受接管的排放。

到2050年，全世界用在收受接管的废钢供给量可能会增长两倍，并且每一单元收受接管的钢铁极可能会孕育发生更多的炉渣。跟着修建质料效率的提高，这条线路可以满意将来全世界对于水泥的需求。

▲ Abstract：

Cement production causes 7.5% of global anthropogenic CO2 emissions, arising from limestone decarbonation and fossil-fuel combustion. Current decarbonation strategies include substituting Portland clinker with supplementary materials, but these mainly arise in emitting processes, developing alternative binders but none yet promises scale, or adopting carbon capture and storage that still releases some emissions. However, used cement is potentially an abundant, decarbonated feedstock. Here we show that recovered cement paste can be reclinkered if used as a partial substitute for the lime dolomite flux used in steel recycling nowadays. The resulting slag can meet existing specifications for Portland clinker and can be blended effectively with calcined clay and limestone. The process is sensitive to the silica content of the recovered cement paste, and silica and alumina that may come from the scrap, but this can be adjusted easily. We show that the proposed process may be economically competitive, and if powered by emissions-free electricity, can lead to zero emissions cement while also reducing the emissions of steel recycling by reducing lime flux requirements. The global supply of scrap steel for recycling may treble by 2050, and it is likely that more slag can be made per unit of steel recycled. With material efficiency in construction future global cement requirements could be met by this route.

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