编译 | 未玖

Science, 21 FEB 2025, VOL 387, ISSUE 6736

《科学》2025年2月21日，第387卷，6736期

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材料科学Materials Science

Interfacial bonding enhances thermoelectric cooling in 3D-printed materials

界面结合增强了3D打印材料的热电冷却

▲ 作者：SHENGDUO XU, SHARONA HORTA, ABAYOMI LAWAL, KRISHNENDU MAJI, MAGALI LORION AND MARIA IBá?EZ

▲ 链接：https://www.science.org/doi/10.1126/science.ads0426

▲ 摘要：热电冷却器（TECs）在现代热管理中至关重要，但在效率和制造可扩展性方面存在局限性。

研究组通过使用挤出式3D打印技术来制造高性能热电材料，以解决这些挑战。该打印墨水配方确保了3D打印结构的完整性和烧结过程中的颗粒间有效结合，在室温下，p型碲化铋锑[(Bi,Sb)₂Te₃]和n型硒化银（Ag₂Se）材料的无量纲热电优值（zT）分别达到创纪录的1.42和1.3。所得TEC在空气中的冷却温度梯度为50℃。

此外，这种可扩展且具有成本效益的方法绕过了高能耗和耗时的步骤（例如铸锭制备和随后的加工过程），为热电器件生产提供了一种革命性的解决方案，预示着高效和可持续热电技术的新时代。

▲ 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过程中锁孔不稳定性的磁调制

▲ 作者：XIANQIANG FAN, TRISTAN G. FLEMING, SAMUEL J. CLARK, KAMEL FEZZAA, ANNA C. M. GETLEY, SEBASTIAN MARUSSI, ET AL.

▲ 链接：https://www.science.org/doi/10.1126/science.ado8554

▲ 摘要：激光焊接和激光粉末床熔合（LPBF）过程中的锁孔不稳定会导致锁孔坍塌和孔洞形成。

利用高速X射线成像，研究组证明了涡流诱导的锁孔后壁突出是引发锁孔不稳定的关键因素。施加横向磁场，通过二次热电磁流体动力学（TEMHD）驱动的流动来改变净涡流分布，从而抑制锁孔的不稳定性。这最大限度地减少了突出和大振幅的锁孔振荡。

抑制效果取决于相对于磁场方向的激光扫描方向，因为这控制了塞贝克效应诱导的洛伦兹力方向。结果表明，在LPBF长度尺度下，电磁阻尼效应较弱，对于塞贝克系数较大的合金，TEMHD成为控制锁孔后流动的主导机制。

▲ 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

具有强度和形状时空控制的类材料机器人集合体

▲ 作者：MATTHEW R. DEVLIN, SANGWOO KIM, OTGER CAMPS AND ELLIOT W. HAWKES

▲ 链接：https://www.science.org/doi/10.1126/science.ads7942

▲摘要：机器人材料的愿景（机器人单元的自组织集合体，能够排列成具有可调控物理性质的任何形式）长期以来一直引起科学界和科幻界的兴趣。然而，这一愿景需要克服一个基本的物理挑战：集合体必须强大以支持负荷，但也能发生形变以采取新的形式。

研究组通过调节单元间的剪切力来控制密堆积结构中单元的拓扑重排，从而在类材料机器人集合体中实现了这一点。这实现了在集合体中局部控制固体状态和流体状态之间的刚性转换，以及对形状和强度的时空控制。

研究组展示了结构形成和愈合，并展示了在自身重量下发生形变之前，集合体能够承重700牛顿（机器人重量的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.

化学Chemistry

Spiro-C(sp3)-atom transfer: Creating rigid three-dimensional structures with Ph2SCN2

螺C（sp3）-原子转移：用Ph₂SCN₂创建刚性三维结构

▲ 作者：QIU SUN, JAN-NIKLAS BELTING, JULIAN HAUDA, DAVID TYMANN, PATRICK W. ANTONI, RICHARD GODDARD, ET AL.

▲ 链接：https://www.science.org/doi/10.1126/science.ads5974

▲ 摘要：将单个C原子引入有机底物通常会形成含有不饱和C（sp）中心的平面分子。添加一个由四个σ-C-C键包围的单个C（sp3）—原子，构建三维立体结构，是合成化学中尚未解决的挑战。

研究组报道了重氮硫叶立德Ph2S=C=N2试剂的合成和应用，该试剂结合了硫叶立德和重氮化合物的反应性，通过顺序或单步构建C（sp3）—原子以通用方式产生螺碳中心。以C（sp3）—原子为中心可以形成新的C-C和C-X（其中X为O或N）键，最终可在无需借助过渡金属催化的情况下一步形成4个C-C σ-键。

Ph₂SCN₂也可用于制备含有氧杂螺[2.2]戊烷以及三环螺旋化合物的高张力骨架。

▲ 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

可见光引发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.

▲ 链接：https://www.science.org/doi/10.1126/science.adr1637

▲摘要：将具有碳—碳骨架的乙烯基聚合物转化为单体是缓解日益增长的塑料废物流的理想途径。然而，解聚这种稳定的材料仍颇具挑战，最先进的方法依赖于既非商业化生产也不适合实际应用的“设计”聚合物。

在这项工作中，研究组报道了一种主链引发、可见光触发的解聚，直接适用于含有未公开杂质（如共聚单体、添加剂或染料）的商业聚合物。

通过直接从溶剂中原位生成氯自由基，可以实现聚甲基丙烯酸酯的近定量（>98%）解聚，而不受合成路线（如自由基聚合或离子聚合）、端基和分子量（高达160万道尔顿）的限制。进行多克级解聚和赋予时间控制的可能性使这种方法成为一种通用回收途径。

▲ 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.

地球科学Earth Science

Hidden cascades of seismic ice stream deformation

隐藏的地震性冰流变形级联

▲ 作者：ANDREAS FICHTNER, COEN HOFSTEDE, BRIAN L. N. KENNETT, ANDERS SVENSSON, JULIEN WESTHOFF, FABIAN WALTER, ET AL.

▲ 链接：https://www.science.org/doi/10.1126/science.adp8094

▲摘要：冰流是海平面变化的主要调节器。然而，由于对相关过程的不完全理解，人们对冰流演变的标准粘性流动模拟的预测能力有限。

在格陵兰冰盖上，基于钻孔光纤的观测揭示了一种与粘性流动理论不符的脆性变形模式，其长度尺度与现代冰盖模型的分辨率相似：即在地表无法观测到的冰震级联效应。冰震级联在火山来源杂质附近成核，促进晶界开裂，表现为晶体尺度原初塑性的宏观形式。

保守估计表明，冰震级联或产生与大地测量值振幅相当的应变率，从而在当前冰盖模型和观测之间提供了一个可能缺失的关联机制。

▲ 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.