@article{21721, abstract = {Swimming bacteria move through a fluid by actuating their moving body parts. They are force-free and can be described as hydrodynamic force dipoles: pushers or pullers. This modelling description is broadly used in biological physics and active matter research, and it has successfully predicted, for example, the superfluid behaviour of suspensions of pushers or the bend instability and emergence of turbulent flows in active nematics. However, this description accounts only for the translational motion of the swimming body and neglects the effects of hydrodynamic torque dipoles, which are relevant to bacteria with rotary motor-driven flagella, such as swimming Escherichia coli. Here we show that the torque dipole of confined swimming E. coli can power the persistent rotation of symmetric discs. The torque dipole leads to a traction force on the discs, an additive mechanism that is both contactless and independent of the orientation of the bacteria. Our results indicate that the torque dipole of swimming E. coli is notable in confined geometries, which is relevant to bacterial transport through porous materials, biofilms and the development of chiral fluids.}, author = {Grober, Daniel B and Dhar, Tanumoy and Saintillan, David and Palacci, Jérémie A}, issn = {1745-2481}, journal = {Nature Physics}, publisher = {Springer Nature}, title = {{The hydrodynamic torque dipole from rotary bacterial flagella powers symmetric discs}}, doi = {10.1038/s41567-026-03189-4}, year = {2026}, } @article{19998, abstract = {nspired by Richard Feynman’s 1959 lecture and the 1966 film Fantastic Voyage, the field of micro/nanorobots has evolved from science fiction to reality, with significant advancements in biomedical and environmental applications. Despite the rapid progress, the deployment of functional micro/nanorobots remains limited. This review of the technology roadmap identifies key challenges hindering their widespread use, focusing on propulsion mechanisms, fundamental theoretical aspects, collective behavior, material design, and embodied intelligence. We explore the current state of micro/nanorobot technology, with an emphasis on applications in biomedicine, environmental remediation, analytical sensing, and other industrial technological aspects. Additionally, we analyze issues related to scaling up production, commercialization, and regulatory frameworks that are crucial for transitioning from research to practical applications. We also emphasize the need for interdisciplinary collaboration to address both technical and nontechnical challenges, such as sustainability, ethics, and business considerations. Finally, we propose a roadmap for future research to accelerate the development of micro/nanorobots, positioning them as essential tools for addressing grand challenges and enhancing the quality of life.}, author = {Ju, Xiaohui and Chen, Chuanrui and Oral, Cagatay M. and Sevim, Semih and Golestanian, Ramin and Sun, Mengmeng and Bouzari, Negin and Lin, Xiankun and Urso, Mario and Nam, Jong Seok and Cho, Yujang and Peng, Xia and Landers, Fabian C. and Yang, Shihao and Adibi, Azin and Taz, Nahid and Wittkowski, Raphael and Ahmed, Daniel and Wang, Wei and Magdanz, Veronika and Medina-Sánchez, Mariana and Guix, Maria and Bari, Naimat and Behkam, Bahareh and Kapral, Raymond and Huang, Yaxin and Tang, Jinyao and Wang, Ben and Morozov, Konstantin and Leshansky, Alexander and Abbasi, Sarmad Ahmad and Choi, Hongsoo and Ghosh, Subhadip and Borges Fernandes, Bárbara and Battaglia, Giuseppe and Fischer, Peer and Ghosh, Ambarish and Jurado Sánchez, Beatriz and Escarpa, Alberto and Martinet, Quentin and Palacci, Jérémie A and Lauga, Eric and Moran, Jeffrey and Ramos-Docampo, Miguel A. and Städler, Brigitte and Herrera Restrepo, Ramón Santiago and Yossifon, Gilad and Nicholas, James D. and Ignés-Mullol, Jordi and Puigmartí-Luis, Josep and Liu, Yutong and Zarzar, Lauren D. and Shields, C. Wyatt and Li, Longqiu and Li, Shanshan and Ma, Xing and Gracias, David H. and Velev, Orlin and Sánchez, Samuel and Esplandiu, Maria Jose and Simmchen, Juliane and Lobosco, Antonio and Misra, Sarthak and Wu, Zhiguang and Li, Jinxing and Kuhn, Alexander and Nourhani, Amir and Maric, Tijana and Xiong, Ze and Aghakhani, Amirreza and Mei, Yongfeng and Tu, Yingfeng and Peng, Fei and Diller, Eric and Sakar, Mahmut Selman and Sen, Ayusman and Law, Junhui and Sun, Yu and Pena-Francesch, Abdon and Villa, Katherine and Li, Huaizhi and Fan, Donglei Emma and Liang, Kang and Huang, Tony Jun and Chen, Xiang-Zhong and Tang, Songsong and Zhang, Xueji and Cui, Jizhai and Wang, Hong and Gao, Wei and Kumar Bandari, Vineeth and Schmidt, Oliver G. and Wu, Xianghua and Guan, Jianguo and Sitti, Metin and Nelson, Bradley J. and Pané, Salvador and Zhang, Li and Shahsavan, Hamed and He, Qiang and Kim, Il-Doo and Wang, Joseph and Pumera, Martin}, issn = {1936-086X}, journal = {ACS Nano}, number = {27}, pages = {24174--24334}, publisher = {American Chemical Society}, title = {{Technology roadmap of micro/nanorobots}}, doi = {10.1021/acsnano.5c03911}, volume = {19}, year = {2025}, } @article{20218, abstract = {Humanity has long sought inspiration from nature to innovate materials and devices. As science advances, nature-inspired materials are becoming part of our lives. Animate materials, characterized by their activity, adaptability, and autonomy, emulate properties of living systems. While only biological materials fully embody these principles, artificial versions are advancing rapidly, promising transformative impacts in the circular economy, health and climate resilience within a generation. This roadmap presents authoritative perspectives on animate materials across different disciplines and scales, highlighting their interdisciplinary nature and potential applications in diverse fields including nanotechnology, robotics and the built environment. It underscores the need for concerted efforts to address shared challenges such as complexity management, scalability, evolvability, interdisciplinary collaboration, and ethical and environmental considerations. The framework defined by classifying materials based on their level of animacy can guide this emerging field to encourage cooperation and responsible development. By unravelling the mysteries of living matter and leveraging its principles, we can design materials and systems that will transform our world in a more sustainable manner.}, author = {Volpe, Giorgio and Araújo, Nuno A.M. and Guix, Maria and Miodownik, Mark and Martin, Nicolas and Alvarez, Laura and Simmchen, Juliane and Leonardo, Roberto Di and Pellicciotta, Nicola and Martinet, Quentin and Palacci, Jérémie A and Ng, Wai Kit and Saxena, Dhruv and Sapienza, Riccardo and Nadine, Sara and Mano, João F. and Mahdavi, Reza and Beck Adiels, Caroline and Forth, Joe and Santangelo, Christian and Palagi, Stefano and Seok, Ji Min and Webster-Wood, Victoria A. and Wang, Shuhong and Yao, Lining and Aghakhani, Amirreza and Barois, Thomas and Kellay, Hamid and Coulais, Corentin and Van Hecke, Martin and Pierce, Christopher J. and Wang, Tianyu and Chong, Baxi and Goldman, Daniel I. and Reina, Andreagiovanni and Trianni, Vito and Volpe, Giovanni and Beckett, Richard and Nair, Sean P. and Armstrong, Rachel}, issn = {1361-648X}, journal = {Journal of Physics Condensed Matter}, number = {33}, publisher = {IOP Publishing}, title = {{Roadmap for animate matter}}, doi = {10.1088/1361-648X/adebd3}, volume = {37}, year = {2025}, } @article{19441, abstract = {Catalytic microswimmers convert the chemical energy from fuel into motion. They sustain chemical gradients and fluid flows that propel them by phoresis. This leads to unconventional behavior and collective dynamics, such as self-organization into complex structures. Characterizing the nonequilibrium interactions of microswimmers is crucial for advancing our understanding of active systems. However, this remains a challenge owing to the importance of fluctuations at the microscale and the difficulty in disentangling the different contributions to the interactions. Here, we show a massive dependence of the nonequilibrium interactions on the shape of catalytic microswimmers. We perform tracking experiments at high throughput to map interactions between nanocolloidal tracers and dimeric microswimmers of various aspect ratios. Our method leverages dual tracers with differing phoretic mobilities to quantitatively disentangle phoretic motion from hydrodynamic advection. This approach is validated through experiments on single chemically active sites and on immobilized catalytic microswimmers. We further investigate the activity-driven interactions of free microswimmers and directly measure their phoretic interactions. When compared to standard models, our findings highlight the important role of osmotic flows for microswimmers near surfaces and reveal an enhanced contribution of hydrodynamic advection relative to phoretic motion as the size of the microswimmer increases. Our study provides robust measurements of the nonequilibrium interactions from catalytic microswimmers and lays the groundwork for a realistic description of active systems.}, author = {Carrasco, Celso and Martinet, Quentin and Shen, Zaiyi and Lintuvuori, Juho and Palacci, Jérémie A and Aubret, Antoine}, issn = {1936-086X}, journal = {ACS Nano}, number = {11}, pages = {11133--11145}, publisher = {American Chemical Society}, title = {{Characterization of nonequilibrium interactions of catalytic microswimmers using phoretically responsive nanotracers}}, doi = {10.1021/acsnano.4c18078}, volume = {19}, year = {2025}, } @article{20708, abstract = {In equilibrium, the physical properties of matter are set by the interactions between the constituents. In contrast, the energy input of the individual components controls the behavior of synthetic or living active matter. Great progress has been made in understanding the emergent phenomena in active fluids, though their inability to resist shear forces hinders their practical use. This motivates the exploration of active solids as shape-shifting materials, yet, we lack controlled synthetic systems to devise active solids with unconventional properties. Here we build active elastic beams from dozens of active colloids and unveil complex emergent behaviors such as self-oscillations or persistent rotations. Developing tensile tests at the microscale, we show that the active beams are ultrasoft materials, with large (nonequilibrium) fluctuations. Combining experiments, theory, and stochastic inference, we show that the dynamics of the active beams can be mapped on different phase transitions which are tuned by boundary conditions. More quantitatively, we assess all relevant parameters by independent measurements or first-principles calculations, and find that our theoretical description agrees with the experimental observations. Our results demonstrate that the simple addition of activity to an elastic beam unveils novel physics and can inspire design strategies for active solids and functional microscopic machines.}, author = {Martinet, Quentin and Li, Yuting I and Aubret, A. and Hannezo, Edouard B and Palacci, Jérémie A}, issn = {2160-3308}, journal = {Physical Review X}, number = {4}, publisher = {American Physical Society}, title = {{Emergent dynamics of active elastic microbeams}}, doi = {10.1103/rjk2-q2wh}, volume = {15}, year = {2025}, } @article{13971, abstract = {When in equilibrium, thermal forces agitate molecules, which then diffuse, collide and bind to form materials. However, the space of accessible structures in which micron-scale particles can be organized by thermal forces is limited, owing to the slow dynamics and metastable states. Active agents in a passive fluid generate forces and flows, forming a bath with active fluctuations. Two unanswered questions are whether those active agents can drive the assembly of passive components into unconventional states and which material properties they will exhibit. Here we show that passive, sticky beads immersed in a bath of swimming Escherichia coli bacteria aggregate into unconventional clusters and gels that are controlled by the activity of the bath. We observe a slow but persistent rotation of the aggregates that originates in the chirality of the E. coli flagella and directs aggregation into structures that are not accessible thermally. We elucidate the aggregation mechanism with a numerical model of spinning, sticky beads and reproduce quantitatively the experimental results. We show that internal activity controls the phase diagram and the structure of the aggregates. Overall, our results highlight the promising role of active baths in designing the structural and mechanical properties of materials with unconventional phases.}, author = {Grober, Daniel and Palaia, Ivan and Ucar, Mehmet C and Hannezo, Edouard B and Šarić, Anđela and Palacci, Jérémie A}, issn = {1745-2481}, journal = {Nature Physics}, pages = {1680--1688}, publisher = {Springer Nature}, title = {{Unconventional colloidal aggregation in chiral bacterial baths}}, doi = {10.1038/s41567-023-02136-x}, volume = {19}, year = {2023}, } @article{12822, abstract = {Gears and cogwheels are elemental components of machines. They restrain degrees of freedom and channel power into a specified motion. Building and powering small-scale cogwheels are key steps toward feasible micro and nanomachinery. Assembly, energy injection, and control are, however, a challenge at the microscale. In contrast with passive gears, whose function is to transmit torques from one to another, interlocking and untethered active gears have the potential to unveil dynamics and functions untapped by externally driven mechanisms. Here, it is shown the assembly and control of a family of self-spinning cogwheels with varying teeth numbers and study the interlocking of multiple cogwheels. The teeth are formed by colloidal microswimmers that power the structure. The cogwheels are autonomous and active, showing persistent rotation. Leveraging the angular momentum of optical vortices, we control the direction of rotation of the cogwheels. The pairs of interlocking and active cogwheels that roll over each other in a random walk and have curvature-dependent mobility are studied. This behavior is leveraged to self-position parts and program microbots, demonstrating the ability to pick up, direct, and release a load. The work constitutes a step toward autonomous machinery with external control as well as (re)programmable microbots and matter.}, author = {Martinet, Quentin and Aubret, Antoine and Palacci, Jérémie A}, issn = {2640-4567}, journal = {Advanced Intelligent Systems}, number = {1}, publisher = {Wiley}, title = {{Rotation control, interlocking, and self‐positioning of active cogwheels}}, doi = {10.1002/aisy.202200129}, volume = {5}, year = {2023}, } @article{11996, abstract = {If you mix fruit syrups with alcohol to make a schnapps, the two liquids will remain perfectly blended forever. But if you mix oil with vinegar to make a vinaigrette, the oil and vinegar will soon separate back into their previous selves. Such liquid-liquid phase separation is a thermodynamically driven phenomenon and plays an important role in many biological processes (1). Although energy injection at the macroscale can reverse the phase separation—a strong shake is the normal response to a separated vinaigrette—little is known about the effect of energy added at the microscopic level on phase separation. This fundamental question has deep ramifications, notably in biology, because active processes also make the interior of a living cell different from a dead one. On page 768 of this issue, Adkins et al. (2) examine how mechanical activity at the microscopic scale affects liquid-liquid phase separation and allows liquids to climb surfaces.}, author = {Palacci, Jérémie A}, issn = {1095-9203}, journal = {Science}, number = {6607}, pages = {710--711}, publisher = {American Association for the Advancement of Science}, title = {{A soft active matter that can climb walls}}, doi = {10.1126/science.adc9202}, volume = {377}, year = {2022}, } @article{10280, abstract = {Machines enabled the Industrial Revolution and are central to modern technological progress: A machine’s parts transmit forces, motion, and energy to one another in a predetermined manner. Today’s engineering frontier, building artificial micromachines that emulate the biological machinery of living organisms, requires faithful assembly and energy consumption at the microscale. Here, we demonstrate the programmable assembly of active particles into autonomous metamachines using optical templates. Metamachines, or machines made of machines, are stable, mobile and autonomous architectures, whose dynamics stems from the geometry. We use the interplay between anisotropic force generation of the active colloids with the control of their orientation by local geometry. This allows autonomous reprogramming of active particles of the metamachines to achieve multiple functions. It permits the modular assembly of metamachines by fusion, reconfiguration of metamachines and, we anticipate, a shift in focus of self-assembly towards active matter and reprogrammable materials.}, author = {Aubret, Antoine and Martinet, Quentin and Palacci, Jérémie A}, issn = {2041-1723}, journal = {Nature Communications}, number = {1}, publisher = {Springer Nature}, title = {{Metamachines of pluripotent colloids}}, doi = {10.1038/s41467-021-26699-6}, volume = {12}, year = {2021}, }