編譯 | 未玖
Science, 21 FEB 2025, VOL 387, ISSUE 6736
《科學》2025年2月21日，第387卷，6736期
材料科學Materials Science
Interfacial bonding enhances thermoelectric cooling in 3D-printed materials
界面結合增強了3D打印材料的熱電冷卻
▲ 作者：SHENGDUO XU, SHARONA HORTA, ABAYOMI LAWAL, KRISHNENDU MAJI, MAGALI LORION AND MARIA IBá?EZ
▲ 鏈接：https://www.science.org/doi/10.1126/science.ads0426
▲ 摘要：熱電冷卻器（TECs）在現代熱管理中至關重要，但在效率和制造可擴展性方面存在局限性。
研究組通過使用擠出式3D打印技術來制造高性能熱電材料，以解決這些挑戰。該打印墨水配方確保了3D打印結構的完整性和燒結過程中的顆粒間有效結合，在室溫下，p型碲化鉍銻[(Bi,Sb)2Te3]和n型硒化銀（Ag2Se）材料的無量綱熱電優值（zT）分別達到創紀錄的1.42和1.3。所得TEC在空氣中的冷卻溫度梯度為50℃。
此外，這種可擴展且具有成本效益的方法繞過了高能耗和耗時的步驟（例如鑄錠制備和隨后的加工過程），為熱電器件生產提供了一種革命性的解決方案，預示著高效和可持續熱電技術的新時代。
▲ Abstract：Thermoelectric coolers (TECs) are pivotal in modern heat management but face limitations in efficiency and manufacturing scalability. We address these challenges by using an extrusion-based 3D printing technique to fabricate high-performance thermoelectric materials. Our ink formulations ensure the integrity of the 3D-printed structure and effective particle bonding during sintering, achieving record-high figure of merit (zT) values of 1.42 for p-type bismuth antimony telluride [(Bi,Sb)2Te3] and 1.3 for n-type silver selenide (Ag2Se) materials at room temperature. The resulting TEC demonstrates a cooling temperature gradient of 50°C in air. Moreover, this scalable and cost-effective method circumvents energy-intensive and time-consuming steps, such as ingot preparation and subsequently machining processes, offering a transformative solution for thermoelectric device production and heralding a new era of efficient and sustainable thermoelectric technologies.
Magnetic modulation of keyhole instability during laser welding and additive manufacturing
激光焊接和增材制造過程中鎖孔不穩定性的磁調制
▲ 作者：XIANQIANG FAN, TRISTAN G. FLEMING, SAMUEL J. CLARK, KAMEL FEZZAA, ANNA C. M. GETLEY, SEBASTIAN MARUSSI, ET AL.
▲ 鏈接：https://www.science.org/doi/10.1126/science.ado8554
▲ 摘要：激光焊接和激光粉末床熔合（LPBF）過程中的鎖孔不穩定會導致鎖孔坍塌和孔洞形成。
利用高速X射線成像，研究組證明了渦流誘導的鎖孔后壁突出是引發鎖孔不穩定的關鍵因素。施加橫向磁場，通過二次熱電磁流體動力學（TEMHD）驅動的流動來改變凈渦流分布，從而抑制鎖孔的不穩定性。這最大限度地減少了突出和大振幅的鎖孔振蕩。
抑制效果取決于相對于磁場方向的激光掃描方向，因為這控制了塞貝克效應誘導的洛倫茲力方向。結果表明，在LPBF長度尺度下，電磁阻尼效應較弱，對于塞貝克系數較大的合金，TEMHD成為控制鎖孔后流動的主導機制。
▲ Abstract：Keyhole instability during laser welding and laser powder bed fusion (LPBF) can cause keyhole collapse and pore formation. Using high-speed x-ray imaging, we demonstrate that the flow vortex–induced protrusion on the rear keyhole wall is crucial in initiating keyhole instability. Applying a transverse magnetic field suppresses the keyhole instability by driving a secondary thermoelectric magnetohydrodynamics (TEMHD) flow that alters the net flow vortex. This minimizes protrusions and large-amplitude keyhole oscillations. The suppression effectiveness depends on the laser scanning direction relative to the magnetic field orientation because this controls the Seebeck effect–induced Lorentz force’s direction. We show that at LPBF length scales, electromagnetic damping is weak, and for alloys with a large Seebeck coefficient, TEMHD becomes the dominant mechanism controlling flow behind the keyhole.
人工智能Artificial Intelligence
Material-like robotic collectives with spatiotemporal control of strength and shape
具有強度和形狀時空控制的類材料機器人集合體
▲ 作者：MATTHEW R. DEVLIN, SANGWOO KIM, OTGER CAMPS AND ELLIOT W. HAWKES
▲ 鏈接：https://www.science.org/doi/10.1126/science.ads7942
▲摘要：機器人材料的愿景（機器人單元的自組織集合體，能夠排列成具有可調控物理性質的任何形式）長期以來一直引起科學界和科幻界的興趣。然而，這一愿景需要克服一個基本的物理挑戰：集合體必須強大以支持負荷，但也能發生形變以采取新的形式。
研究組通過調節單元間的剪切力來控制密堆積結構中單元的拓撲重排，從而在類材料機器人集合體中實現了這一點。這實現了在集合體中局部控制固體狀態和流體狀態之間的剛性轉換，以及對形狀和強度的時空控制。
研究組展示了結構形成和愈合，并展示了在自身重量下發生形變之前，集合體能夠承重700牛頓（機器人重量的500倍）。
▲ Abstract：The vision of robotic materials—cohesive collectives of robotic units that can arrange into virtually any form with any physical properties—has long intrigued both science and fiction. Yet, this vision requires a fundamental physical challenge to be overcome: The collective must be strong, to support loads, yet flow, to take new forms. We achieve this in a material-like robotic collective by modulating the interunit tangential forces to control topological rearrangements of units within a tightly packed structure. This allows local control of rigidity transitions between solid and fluid-like states in the collective and enables spatiotemporal control of shape and strength. We demonstrate structure-forming and healing and show the collective supporting 700 newtons (500 times the weight of a robot) before “melting” under its own weight.
化學Chemistry
Spiro-C(sp3)-atom transfer: Creating rigid three-dimensional structures with Ph2SCN2
螺C（sp3）-原子轉移：用Ph2SCN2創建剛性三維結構
▲ 作者：QIU SUN, JAN-NIKLAS BELTING, JULIAN HAUDA, DAVID TYMANN, PATRICK W. ANTONI, RICHARD GODDARD, ET AL.
▲ 鏈接：https://www.science.org/doi/10.1126/science.ads5974
▲ 摘要：將單個C原子引入有機底物通常會形成含有不飽和C（sp）中心的平面分子。添加一個由四個σ-C-C鍵包圍的單個C（sp3）—原子，構建三維立體結構，是合成化學中尚未解決的挑戰。
研究組報道了重氮硫葉立德Ph2S=C=N2試劑的合成和應用，該試劑結合了硫葉立德和重氮化合物的反應性，通過順序或單步構建C（sp3）—原子以通用方式產生螺碳中心。以C（sp3）—原子為中心可以形成新的C-C和C-X（其中X為O或N）鍵，最終可在無需借助過渡金屬催化的情況下一步形成4個C-C σ-鍵。
Ph2SCN2也可用于制備含有氧雜螺[2.2]戊烷以及三環螺旋化合物的高張力骨架。
▲ Abstract：The introduction of a single C-atom into organic substrates typically results in the formation of flat molecules containing unsaturated C(sp)-centers. Adding a single C(sp3)-atom surrounded by four σ-C–C bonds, which opens up the three-dimensional space, is an unresolved problem in synthetic chemistry. We report the synthesis and application of the diazosulfur ylide Ph2S=C=N2 reagent that combines the reactivity of both sulfur ylides and diazo compounds to create carbon spiro-centers in a general fashion by the sequential or single-step installation of a C(sp3)-atom. New C–C and C–X (where X is O or N) bonds can be created around the C(sp3)-atom, which can ultimately be extended to four C–C σ-bonds in one step without resorting to transition metal catalysis. Ph2SCN2 can also be used to access highly strained frameworks containing (oxa)spiro[2.2]pentanes as well as tricyclic spiro-compounds.
Visible light–triggered depolymerization of commercial polymethacrylates
可見光引發商用聚甲基丙烯酸酯的解聚
▲ 作者：HYUN SUK WANG, MIKHAIL AGRACHEV, HONGSIK KIM, NGHIA P. TRUONG, TAE-LIM CHOI, GUNNAR JESCHKE, ET AL.
▲ 鏈接：https://www.science.org/doi/10.1126/science.adr1637
▲摘要：將具有碳—碳骨架的乙烯基聚合物轉化為單體是緩解日益增長的塑料廢物流的理想途徑。然而，解聚這種穩定的材料仍頗具挑戰，最先進的方法依賴于既非商業化生產也不適合實際應用的“設計”聚合物。
在這項工作中，研究組報道了一種主鏈引發、可見光觸發的解聚，直接適用于含有未公開雜質（如共聚單體、添加劑或染料）的商業聚合物。
通過直接從溶劑中原位生成氯自由基，可以實現聚甲基丙烯酸酯的近定量（>98%）解聚，而不受合成路線（如自由基聚合或離子聚合）、端基和分子量（高達160萬道爾頓）的限制。進行多克級解聚和賦予時間控制的可能性使這種方法成為一種通用回收途徑。
▲ Abstract：The reversion of vinyl polymers with carbon-carbon backbones to their monomers represents an ideal path to alleviate the growing plastic waste stream. However, depolymerizing such stable materials remains a challenge, with state-of-the-art methods relying on “designer” polymers that are neither commercially produced nor suitable for real-world applications. In this work, we report a main chain–initiated, visible light–triggered depolymerization directly applicable to commercial polymers containing undisclosed impurities (e.g., comonomers, additives, or dyes). By in situ generation of chlorine radicals directly from the solvent, near-quantitative (>98%) depolymerization of polymethacrylates could be achieved regardless of their synthetic route (e.g., radical or ionic polymerization), end group, and molecular weight (up to 1.6 million daltons). The possibility to perform multigram-scale depolymerizations and confer temporal control renders this methodology a versatile and general route to recycling.
地球科學Earth Science
Hidden cascades of seismic ice stream deformation
隱藏的地震性冰流變形級聯
▲ 作者：ANDREAS FICHTNER, COEN HOFSTEDE, BRIAN L. N. KENNETT, ANDERS SVENSSON, JULIEN WESTHOFF, FABIAN WALTER, ET AL.
▲ 鏈接：https://www.science.org/doi/10.1126/science.adp8094
▲摘要：冰流是海平面變化的主要調節器。然而，由于對相關過程的不完全理解，人們對冰流演變的標準粘性流動模擬的預測能力有限。
在格陵蘭冰蓋上，基于鉆孔光纖的觀測揭示了一種與粘性流動理論不符的脆性變形模式，其長度尺度與現代冰蓋模型的分辨率相似：即在地表無法觀測到的冰震級聯效應。冰震級聯在火山來源雜質附近成核，促進晶界開裂，表現為晶體尺度原初塑性的宏觀形式。
保守估計表明，冰震級聯或產生與大地測量值振幅相當的應變率，從而在當前冰蓋模型和觀測之間提供了一個可能缺失的關聯機制。
▲ Abstract：Ice streams are major regulators of sea level change. However, standard viscous flow simulations of their evolution have limited predictive power owing to incomplete understanding of involved processes. On the Greenland ice sheet, borehole fiber-optic observations revealed a brittle deformation mode that is incompatible with viscous flow, over length scales similar to the resolution of modern ice sheet models: englacial ice quake cascades that are unobservable at the surface. Nucleating near volcanism-related impurities that promote grain boundary cracking, the ice quake cascades appear as a macroscopic form of crystal-scale wild plasticity. A conservative estimate indicates that seismic cascades are likely to produce strain rates that are comparable in amplitude with those measured geodetically, providing a plausible missing link between current ice sheet models and observations.
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