《自然》（20240530出版）一周論文導讀

編譯 | 馮維維

Nature, Volume 629 Issue 8014, 30 May 2024

《自然》第629卷，8014期，2024年5月30日

物理學Physics

Suppressed thermal transport in silicon nanoribbons by inhomogeneous strain

非均勻應變抑制硅納米帶中的熱輸運

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

▲ 鏈接：

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

▲ 摘要：

納米級結構可以產生極端應變，從而實現前所未有的材料特性，例如定制電子帶隙，提高超導溫度和增強的電催化活性。雖然已知均勻應變對熱流的影響有限，但由于界面和缺陷的共存，非均勻應變的影響仍然難以捉摸。

研究者通過在定制的微器件上彎曲單個硅納米帶引入非均勻應變，并測量其對熱輸運的影響，同時以亞納米分辨率表征應變相關的振動譜，從而解決了這一空白。

研究結果表明，每納米0.112%的應變梯度可以導致熱導率急劇下降34±5%，與均勻應變下測量的幾乎恒定值形成鮮明對比。研究者進一步利用電子能量損失譜繪制了局部晶格振動譜，這揭示了聲子沿應變梯度的峰值位移為數百萬電子伏特。

第一性原理計算證明，這種獨特的聲子譜展寬效應增強了聲子散射，極大地阻礙了熱輸運。研究揭示了長期存在的非均勻應變下晶格動力學難題的一個關鍵部分，這在均勻應變下是不存在的，并且超出了傳統的理解。

▲ 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

高能效自振蕩聚合物制冷機

▲ 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

▲ 鏈接：

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

▲ 摘要：

介電材料中同時存在著電熱和電致伸縮效應。結合這兩種效果可以實現輕量化，緊湊的局部熱管理，這是由電熱制冷所承諾的。盡管有一些數值模型和示意圖，目前的電熱冰箱仍然依賴于外部附件來驅動工作體，因此導致設備級冷卻功率密度和性能系數（COP）較低。

研究者報告了一種利用聚合鐵電體提供的電熱機械協同作用的電熱薄膜裝置。在一次交流電刺激下，該裝置由工作體自身進行熱循環和機械循環，形成無外部驅動、自循環的軟冰箱。

該原型提供了直接測量的冷卻功率密度為6.5 W g-1，在零溫度范圍下的峰值COP超過58。該器件僅為30微米厚的聚合物薄膜，在開放環境中，在4K的溫度范圍內實現了接近24的COP（32%的熱力學效率）。

與被動冷卻相比，薄膜冰箱可以立即對電子芯片產生17.5 K的額外溫度下降。柔軟的聚合物冰箱可以感知、驅動和泵送熱量，以提供自動的局部熱管理。

▲ 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-μm-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 immediately 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

應變不變可拉伸射頻電子學

▲ 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

▲ 鏈接：

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

▲ 摘要：

無線模塊通過射頻（RF）電子器件提供通信和能量收集功能，是皮膚界面可拉伸電子器件的重要組成部分。然而，最近對可拉伸射頻元件的研究表明，即使在相對較低的彈性應變下，電性能也會發生實質性變化，例如天線諧振頻率的移位。

這種變化直接導致可拉伸系統中的無線信號強度或功率傳輸效率大大降低，特別是在諸如皮膚表面的物理動態環境中。研究者提出了應變不變的可拉伸射頻電子元件，能夠在各種彈性應變下完全保持原始射頻特性，使用“介電彈性”材料作為襯底。

介電彈性材料具有物理可調諧的介電特性，可有效地避免射頻電子接口中產生的頻移。與傳統的可拉伸基板材料相比，這種材料具有優越的電氣、機械和熱性能，適用于高性能可拉伸射頻電子設備。

研究者描述了材料、制造和設計策略，這些策略是基于實驗和計算研究實現關鍵射頻元件應變不變行為的基礎。最后，作者提出了一套基于應變不變可拉伸射頻電子器件的皮膚接口無線醫療監視器，其在應變下的無線操作距離可達30米。

▲ Abstract：

Wireless modules that provide telecommunications 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.

電子信息學Electronic informatics

A vision chip with complementary pathways for open-world sensing

具有開放世界傳感互補路徑的視覺芯片

▲ 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

▲ 鏈接：

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

▲ 摘要：

在開放世界應用中，圖像傳感器在處理動態、多樣化和不可預測的場景時面臨著巨大的挑戰。然而，圖像傳感器向高速、高分辨率、大動態范圍和高精度方向發展受到功率和帶寬的限制。

研究者提出了一種受人類視覺系統啟發的互補感知范式，該范式涉及將視覺信息解析為基于原語的表示，并將這些原語組合成兩條互補的視覺路徑：用于準確認知的以認知為導向的路徑和用于快速反應的以行動為導向的路徑。

為實現這一范式，研究者開發了一種名為“天眸芯”的視覺芯片，該芯片結合了混合像素陣列和并行異構讀出架構。利用互補視覺路徑的特性，天眼實現了高達10,000 fps的高速傳感，130 dB的動態范圍，在空間分辨率，速度和動態范圍方面都是先進的數字。

此外，它自適應地減少了90%的帶寬。他們展示了將天眸芯集成到自動駕駛系統中的能力，即使在開放道路上具有挑戰性的角落情況下，也能實現準確、快速和強大的感知。基于原始的互補傳感范式有助于克服開發用于各種開放世界應用的視覺系統的基本限制。

▲ 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

帶有事件攝像頭的低延遲汽車視覺

▲ 作者：Daniel Gehrig & Davide Scaramuzza

▲ 鏈接：

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

▲ 摘要：

目前，高級駕駛輔助系統中使用的計算機視覺算法依賴于基于圖像的RGB攝像頭，為了提供安全的駕駛體驗，帶寬延遲是一個關鍵的權衡。為了解決這個問題，事件攝像機已經成為另一種視覺傳感器。

事件相機異步測量強度的變化，提供高時間分辨率和稀疏性，顯著降低帶寬和延遲要求。盡管有這些優點，基于事件相機的算法要么效率很高，但在準確性方面落后于基于圖像的算法，要么犧牲事件的稀疏性和效率來獲得類似的結果。

為了克服這個問題，研究者提出了一種基于事件和幀的混合對象檢測器，它保留了每種模式的優點，因此不會受到這種權衡的影響。該方法利用事件的高時間分辨率和稀疏性以及標準圖像中豐富但低時間分辨率的信息來生成高效，高速率的目標檢測，減少感知和計算延遲。

研究表明，使用每秒20幀的RGB相機加上事件相機可以實現與每秒45幀相機帶寬的5000幀相機相同的延遲，而不會影響精度。該方法通過揭示事件相機的潛力，為在邊緣情況下實現高效和穩健的感知鋪平了道路。

▲ 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

大規模水泥電回收

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

▲ 鏈接：

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

▲ 摘要：

水泥生產造成了全球7.5%的人為二氧化碳排放，這是由石灰石脫碳和化石燃料燃燒引起的。目前的脫碳策略包括用補充材料取代波特蘭熟料，但這些主要出現在排放過程中，開發替代粘合劑但尚未達到規模，或者采用仍然釋放一些排放的碳捕獲和儲存。

然而，用過的水泥是一種潛在的豐富的脫碳原料。作者研究表明，回收的水泥漿可以再熟化，如果作為部分替代石灰白云石助熔劑用于目前的鋼鐵回收。所得礦渣滿足現有硅酸鹽熟料的要求，可與煅燒粘土和石灰石有效混合。

該工藝對回收的水泥膏體的二氧化硅含量以及可能來自廢料的二氧化硅和氧化鋁含量很敏感，但這可以很容易地調整。研究表明，擬議的工藝可能具有經濟競爭力，如果由無排放的電力供電，可以實現零排放水泥，同時還可以通過減少石灰助熔劑需求來減少鋼鐵回收的排放。

到2050年，全球用于回收的廢鋼供應量可能會增加兩倍，而且每單位回收的鋼鐵很可能會產生更多的爐渣。隨著建筑材料效率的提高，這條路線可以滿足未來全球對水泥的需求。

▲ 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.