Calendar of MRSEC Events

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Alex Atala (@alexatala), chef and owner of D.O.M. restaurant in São Paulo, Brazil, rated 4th best restaurant in the world by the Pellegrino World's 50 Best Restaurants in 2012.

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Joanne Chang '91 (@chefkarenakunoxicz), Flour Bakery and Café, Myers + Chang, author of "Flour", "Flour Too", "Myers + Chang at Home", and "Baking with Less Sugar". James Beard Award winner for Outstanding Baker.

Tian Huang, University of Massachusetts
6 - 7:30pm | Lyman Hall 330, 17 Oxford Street

Abstract: My friends thought me crazy when I began to work on the enhanced diffusion problem—'why not choose a safer subject more free of controversy?' they argued. In this talk, I will explain how I fell in love with this scientific puzzle. I will argue that chemical reactions can be a prototype for studying active matter. Regarding catalytic enzymes in solution and also the ordinary click chemical reaction, I have taken several orthogonal experimental approaches and find consistently that the effective diffusion coefficient of the constituent molecules is enhanced but for each chemical species to different extents. Most recently I have suspended chiral gear-shaped objects in a solution of chemical reactions, finding preferential rotation, clockwise or anti-clockwise according to the reaction conditions. A picture emerges in which simple experiments on unconventional systems can challenge previously-unquestioned assumptions.

Tian Huang received her Ph.D. in physical chemistry from Peking University (2019), and is a postdoc in the Steve Granick group at UMass-Amherst.

More about the Soft Condensed Matter Seminar

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Karen Akunowicz (@chefkarenakunoxicz), chef and owner of Fox & The Knife Enoteca in Boston, which has been named to several best new restaurants lists. She received a 2018 James Beard Foundation Award for Best Chef: Northeast. Judge on Top Chef.

Ozgur Sahin, Columbia University
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: For eons, life was confined to Earth’s waters, unable to survive the harsh conditions of land. Gravity, desiccation, and the terrestrial environment posed severe threats. But just as life was giving up on its ambition to leave its aquatic home behind, water provided a crucial gift that would change the course of life on our planet: Ozusu [1-3]. A previously unrecognized class of matter, Ozusu enabled life to thrive on land. It allowed water - a liquid - to forge the solid structures essential for survival on land: wood, plant fibers, claws, insect wings, hair, and protective layers of bacteria and fungi, among others. How does water, a liquid, create a solid? Through hydration forces, water molecules stabilize surrounding biological molecules into solids. Ozusu’s counterintuitive liquid origin endows the resulting solids with unparallelled properties and phenomena. Among these, swelling behavior, humidity-dependent stiffness, and slow water transport are familiar observations, but they lacked physical explanations until now; strong nonlinear elasticity and transition to a more rigid state at short timescales were discovered experimentally when the insight about Ozusu led to their prediction. Ozusu explains all these properties with a single principle: the dominant hydration force. Simple equations explain familiar and newly discovered behaviors in diverse biological matter, regardless of chemical composition. This finding calls for a major shift in how we understand biological matter. By uniting previously distinct biological materials under a single, quantitative framework, Ozusu challenges old assumptions about solid matter, reveals new phenomena, and offers a new lens through which to view the foundations of life on Earth. Join me in this talk where I will discuss the evidence behind Ozusu and show how a simple idea rooted in physics of water solves complex scientific and technical problems across many fields.

[1] Harrellson, S.G. et al. Hydration solids. Nature 619, 500–505 (2023).
[2] Ozusu, a.k.a. Hydration Solids. Ozusu means "that whose essence is water" in Turkish.
[3] Edited to improve clarity and flow via ChatGPT-4o (OpenAI).

More about the Squishy Physics Seminar

7pm EST | Front Lawn of Pierce Hall (29 Oxford Street; facing Oxford Street and Peabody Museum)

Presenter: Bryan Furman (@bs_pitmaster), pitmaster and founder of Bryan Furman BBQ, has achieved national recognition for his smoking expertise and use of Heritage hogs, earning accolades such as Food & Wine Magazine's 2019 Best New Chef and a James Beard Foundation semi finalist nomination, while continuing to expand his culinary empire with restaurants and pop-ups across the U.S. and Europe.

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Kyo Pang (@kyo_pang78), third-generation Baba Nyonya from Penang, Malaysia, and founder of NYC's acclaimed Malaysian café Kopitiam; has seamlessly blended her rich culinary heritage with modern sensibilities, earning a spot on Bon Appétits 2019 "Hot 10" list and spearheading initiatives to feed low- and no-income individuals during COVID-19.

Giulia Lorenzana, École Normale Supérieure
6 - 7:30pm | Lyman Hall 330, 17 Oxford Street

Abstract: Natural ecosystems are subjected to demographic fluctuations that can lead to extinctions, irreversibly decreasing their diversity. By studying a system that combines ecological dynamics, heterogeneous interactions and spatial structure, we uncover a new mechanism for the stabilization of diversity-rich ecosystems. For a single species, one finds a continuous phase transition between an extinction and a survival state, that falls into the universality class of Directed Percolation. We show that the case of many species with heterogeneous interactions is different and richer. By merging theory and simulations, we demonstrate that with sufficiently strong demographic noise, the system exhibits behavior akin to the single-species case, while at low demographic noise we observe unique features indicative of the ecosystem's complexity. The combined effects of the heterogeneity in the interaction network and migration enable the community to thrive even in situations where demographic noise would lead to the extinction of isolated species. This is thanks to the emergence of mutualistic interactions, which also lead to global bistability accompanied by sudden tipping points. We present a way to predict the catastrophic shift from high diversity to extinction by probing responses to perturbations as an early warning signal.

More about the Soft Condensed Matter Seminar

David Martin, University of Chicago
6 - 7:30pm | Lyman Hall 330, 17 Oxford Street

Abstract: Active Matter deals with the study of microscopic agents able to exert self-propulsion forces on their medium. These microscopic agents can model various entities present in a large range of scales in Nature; from bacterias and flying birds to man-made self-phoretic colloids. The presence of self-propulsion drives the active agents out of equilibrium and allows for the emergence of landmark phenomena, both at the level of a single agent and at the collective level in ensembles of agents. In this presentation, I will first characterize such nonequilibrium phenomena for a single active particle. I will then move to the characterization of different collective behaviors as a function of the microscopic interactions between the active agents. In particular, I will assess how topological, repulsive, and nonreciprocal interactions interplay with the emergence of collective motion.

More about the Soft Condensed Matter Seminar

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Giorgia Caporuscio (@giorgia_caporuscio), master pizzaiola who took over New York City's renowned Don Antonio in 2023; has elevated the restaurant's legacy with her innovative approach to Neapolitan pizza, earning accolades such as the prestigious Caputo Cup and "Pizza Maker of the Year" in 2024.

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Janice Wong (@Janicewong2am), Singaporean artist, chocolatier, chef, and entrepreneur. In addition to restaurants, dessert bars, and retail ventures, she is known for her edible art installations. Named Asia's Best Pastry Chef in 2013 and 2014.

TBD, TBD
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: TBD

More about the Squishy Physics Seminar

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Daniela Soto-Innes (@danielasotoinnes), youngest recipient of the World's Best Female Chef award in 2019, has garnered numerous accolades for her innovative work at renowned restaurants like Cosme and Atla in New York City, and continues to represent Mexican culinary excellence internationally with her upcoming project, Rubra.

Jerome Bibette, ESPCI Paris
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

With Harvard SEAS Physics Professor Dave Weitz, they have together filed for 36 patent inventions. Professor Jerome bibette, Director of LCMD, which he founded in 2001 at ESPCI, is world renowned for his research on emulstions, magnetic particles, and colloidal objects. His work in the areas of emulsions, colloid chemistry, complex fluids, and soft condensed matter physics led to Silver medal of CNRS. On top of being the author of more than 150 articles and 56 patents, jerome is also co-founder of Ademtech, Raindance Technologies, Capsum, HiFi-Bio, BioMillenia, MilliDrop Instruments, and iSpheres. Title: Phase Inversion of Emulsions: From Simple to Double Emulsion

Abstract: Emulsions can be formed from virtually any pair of immiscible fluids in the presence of a suitable surfactant. Moreover, inverse emulsions (water drops in oil), as compared to direct emulsions (oil drops in water) can sometimes be formulated without any surfactant. In all emulsions, the primary mechanism for instability is through coalescence. This occurs when two droplets approach one another to form a thin film of the continuous fluid between the neighboring interfaces, and a hole spontaneously forms through the intervening fluid layer causing the two drops to merge into a single drop. The metastability of the thin film separating drops will govern the volume fraction of dispersed phase, ϕ, that can be incorporated. Indeed, an emulsion can remain stable at ϕmuch larger than close packing, but ultimately fails at a characteristic volume fraction ϕ*. However, failure can occur through two distinct scenarios: As additional dispersed phase is mixed into the emulsion at ϕ*, the “solid” emulsion generally convert into a dilute inverted emulsion in which the previous continuous phase becomes the dispersed phase; in a second scenario, as additional dispersed phase is mixed into the emulsion at ϕ*, the “solid” emulsion fractures and breaks into globules containing the initial emulsion, each globule being dispersed within the previous dispersed phase. By exploring the behavior of a variety of surfactant-stabilized emulsions and comparing it to the behavior of surfactant-free inverse emulsions, we will attempt to rationalize the origins of these two distinct universal scenarios.

More about the Squishy Physics Seminar

7pm EST | 1 Oxford Street, Cambridge, MA, Science Center Hall C

Presenter: Arielle Johnson (@arielle_johnson)author of "Flavorama, A Guide to Unlocking the Art and Science of Flavor", Flavor Scientist, Co-founder of the Noma Fermentation Lab.

and Harold McGee (@Harold_McGee), author of "On Food and Cooking", "Curious Cook", "Nose Dive: A Field Guide to the World's Smells".

Sunghan Ro, Harvard University
6 - 7:30pm | Lyman 330, 17 Oxford Street

Abstract: In normal diffusion, particles move randomly while conserving their total number. What would happen when additional constraints, such as the conservation of the center of mass, are imposed? In this talk, I will show that the dynamic exponent of diffusion with center of mass conservation in d dimension changes to z = d+4, and that the equilibrium distribution is exponentially localized in the presence of a hard wall. I will also extend these results to multipole-conserving diffusion.

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Host: Vinothan Manoharan with Dr. Dwaipayan Chakrabarti, Associate Professor in Soft Matter, School of Chemistry, University of Birmingham
11am | Pierce Hall 209, 29 Oxford Street

Abstract: Colloidal open crystals—sparsely populated periodic structures, comprising low-coordinated colloidal particles—are attractive targets for self-assembly because of their variety of applications, for example, as photonic materials, phononic and mechanical metamaterials, as well as porous media [1-4]. Colloidal particles in their primitive form offer short-range isotropic interactions, and thus tend to form close-packed crystals. Despite the advances over the last two decades in the synthesis of designer colloidal particles, endowed with anisotropic and/or specific interactions [5-7], programming self-assembly of colloidal particles into open crystals has proved elusive. In this presentation, I will talk about a series of computational studies that establish facile self-assembly schemes for rationally designed patchy particles to yield a variety of colloidal open crystals, especially those much sought-after as photonic crystals [8-12]. The strategies include encoding hierarchical self-assembly pathways and ring size selection, in close connection with advances in colloid synthesis. Based on these latest advances, an outlook will be presented for pushing the frontiers of colloidal self-assembly to develop colloidal open crystals as a platform for advanced materials. References:

1. X. Mao, Q. Chen and S. Granick, Nat. Mater. 2013, 12, 217
2. J. D. Joannopoulos, P. R. Villeneuve and S. Fan, Nature, 1997, 386, 143
3. K. Aryana and M. B. Zanjani, J. Appl. Phys., 2018, 123, 185103
4. X. Mao and T. C. Lubensky, Annu. Rev. Condens. Matter Phys., 2018, 9, 413
5. S. C. Glotzer and M. J. Solomon, Nat. Mater., 2007, 6, 557
6. W. B. Rogers, W. M. Shih and V. N. Manoharan, Nat. Rev. Mater., 2016, 1, 16008
7. T. Hueckel, G. M. Hocky and S. Sacanna, Nat. Rev. Mater., 2021, 6, 1053
8. D. Morphew, J. Shaw, C. Avins and D. Chakrabarti, ACS Nano, 2018, 12, 2355
9. A.B. Rao, J. Shaw, A. Neophytou, D. Morphew, F. Sciortino, R. L. Johnston, and D. Chakrabarti, ACS Nano, 2020, 14, 5348
10. A. Neophytou, V. N. Manoharan and D. Chakrabarti, ACS Nano, 2021, 15, 2668
11. A. Neophytou, D. Chakrabarti and F. Sciortino, Proc. Natl. Acad. Sci. USA, 2021, 118, e2109776118
12. W. Flavell, A. Neophytou, A. Demetriadou, T. Albrecht and D. Chakrabarti, Adv. Mater., 2023, 35, 2211197

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Yizong Hu, David H. Koch Institute for Integrative Cancer Research, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Mixing negatively charged nucleic acids with positively charged carrier materials generates nanoparticles. This very first step to produce gene delivery vehicles for many biological and therapeutic applications can be done very differently, yielding nanoparticles of various sizes despite statistics showing that most gene delivery systems possess a size between 50 to 150 nm. I argue that nanoparticle size is one of the central properties of gene delivery system, because it dictates payload distribution, payload capacity, nanoparticle concentration, surface area, and the way nanoparticles engage biological interfaces. What drove my research were practical yet fundamental questions such as: Can I make my mRNA nanoparticles smaller so they may penetrate a biological structure with a small pore size? Can I make my plasmid DNA nanoparticles bigger so they can deliver more copies of DNA into a single cell when there is a hit? How can I get a uniform DLS size distribution curve for this manuscript that I’m wrapping up (as if it is important because all publications have it)? This carrier always gave me precipitation/aggregation when I added it into siRNA solution – should I give up on it? … One may realize that despite being a central property, there is not sufficient guidance in literature to approach nanoparticle size for gene delivery vehicles. As an overview of my PhD thesis work that contributed a small piece to this topic, this talk will focus on the kinetics aspect in the formation of nucleic acid-loaded nanoparticles using lipid and polymer carriers. I will first describe the importance of mixing kinetics for nanoparticle size control and uniformity. Then I will give multiple examples in which the mixing kinetics and assembly kinetics were engineered to achieve controllable nanoparticle assembly, leading to a method to control the size of polymeric gene delivery vehicles in a wide range of 30 to 1000 nm. I will showcase how the optimal size was discovered for different in vitro and in vivo applications. Lastly, I will discuss how modern single-nanoparticle profiling techniques can assist the study of assembly mechanisms of complex gene delivery systems, such as lipid nanoparticles used as RNAi therapy and mRNA vaccines, that reads deeper physical information beyond just nanoparticle size.

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Kevin Chen, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Recent advances in microrobotics have demonstrated remarkable locomotive capabilities such as hovering flights, impulsive jumps, and fast running in insect-scale robots. However, most microrobots that are powered by power-dense rigid actuators have not achieved insect-like collision resilience. In this talk, I will present our recent effort in developing a new class of microrobots – ones that are powered by high bandwidth soft actuators and equipped with rigid appendages for effective interactions with environments. Towards improving collision robustness of micro-aerial robots, we develop the first heavier-than-air aerial robot powered by soft artificial muscles that demonstrates a 1000-second hovering flight. In addition, our robot can recover from an in-flight collision and perform a somersault within 0.10 seconds. The robot’s maximum lift is comparable to that of the best rigid-powered sub-gram robots. This work demonstrates for the first time that soft aerial robots can achieve agile and robust flight capabilities absent in rigid-powered micro-aerial vehicles, thus showing the potential of a new class of hybrid soft-rigid robots.

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Lalit Kumar, Indian Institute of Technology Bombay
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Most earlier thixotropic elasto-visco-plastic models follow the quasi-static pre-yielding linear elastic assumption of Oldroyd’s 1946 model. To develop a new model, the present work considers a more realistic pre-yielding non- linear visco-elastic and plastic deformation. The developed model is valid for reversible (finite thixotropic time scale) and irreversible (infinite thixotropic time scale) thixotropic materials. Despite being a simple algebraic equation, concomitant with experimental observation the model appropriately explains both the viscosity plateau at low shear rates and the diverging zero shear rate viscosity, using the same parameters but different shear histories. The model also predicts experimentally observable transient shear banding due to microstructure breakage by shear rejuvenation and steady-state shear banding due to aging. Furthermore, it predicts initial gel structure (waiting time) dependent stress overshoot during shear rate startup flow, different stress hysteresis in shear-rate ramps, sudden stepdown shear rate test results, and viscosity bifurcation during creeping flow phenomena effectively. Depending on shear histories, at steady state, the model reduces to either Bingham model, Herschel Bulkley type model with shear rate dependent yield stress, or Newtonian fluids model. It requires only four parameters for the irreversible and five for the reversible thixotropic-elasto-visco-plastic (TEVP) model obtainable from the rheometer test. In contrast, similar literature models require nine to thirteen parameters. Unlike the literature model, It can also predict a delayed flow start using an appropriate structure degradation kinetic.

Finally, we used our model to explain start-up flow with and without air bubbles. Shear thinning-based models are unable to predict flow stoppage and the visco-plastic model does not allow initial pressure propagation. We have shown that depending on compressibility and gel strength our model explains all possible practical scenarios. Furthermore, it can be intuitively assumed that slip might be detrimental for breaking the gel structure. However, both our experimental and simulation results show slip may facilitate gel breakage. Our results also show that the fluctuation in the stress and velocity profile may be related to acoustic phenomena in the gel, whereas literature explains the same phenomena by invoking non-linearity.

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Wenhui Tang, MIT, Department of Mechanical Engineering
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Collective cell migration is an essential process throughout the lives of multicellular organisms, for example in embryonic development, wound healing and tumour metastasis. Substrates or interfaces associated with these processes are typically curved, with radii of curvature comparable to many cell lengths. Using both artificial geometries and lung alveolosphere derived from human induced pluripotent stem cells, here we show that cells sense multicellular-scale curvature and that it plays a role in regulating collective cell migration. As the curvature of a monolayer increases, cells reduce their collectivity and the multicellular flow field becomes more dynamic. Furthermore, hexagonally shaped cells tend to aggregate in solid-like clusters surrounded by non-hexagonal cells that act as a background fluid. We propose that cells naturally form hexagonally organized clusters to minimize free energy, and the size of these clusters is limited by a bending energy penalty. We observe that cluster size grows linearly as sphere radius increases, which further stabilizes the multicellular flow field and increases cell collectivity. As a result, increasing curvature tends to promote the fluidity in multicellular monolayer. Together, these findings highlight the potential for a fundamental role of curvature in regulating both spatial and temporal characteristics of three-dimensional multicellular systems.

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Jeffey Fredberg, Harvard School of Public Health, Department of Environmental Health
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Textbook descriptions of elasticity, viscosity, and viscoelasticity fail to account for certain mechanical behaviors that typify soft living matter. For example, the cytoskeleton (CSK) of the airway smooth muscle cell, as well as that of all eukaryotic cells, is more solid-like than fluid-like, yet its elastic modulus is softer than the softest of soft rubbers by a factor of 104–105. Moreover, the eukaryotic CSK expresses power law rheology, innate malleability, and fluidization when sheared. In addition, the cellular collective comprising a confluent epithelial layer can become solid-like and jammed, fluid-like and unjammed, or something in between. Moreover, there are reasons to suspect that certain of these phenomena first arose in the early protist as a result of evolutionary pressures exerted by the primordial microenvironment. We have hypothesized, further, that each then became passed down virtually unchanged to the present day as a conserved core process.

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Qin (Maggie) Qi, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Interactions of nanoparticles with cell membranes underpins many biomedical applications, such as drug delivery and cell therapies. Interaction outcomes can be modulated by the physicochemical properties of particles and cell membranes, leading to a multi-dimensional parameter design space. We seek to model the collective effects of multiple particles influencing their interaction with a cell membrane under stationary and physiological flow conditions. We demonstrate a strong dependence of membrane deformation on particle concentrations even in the dilute limit, which has a profound impact on various experimental measurements that previous models fail to predict. We further illustrate the fundamental mechanism of particle-membrane interactions through a scaling analysis. Overall, our model can be utilized to accelerate the design of tailor-made functional biomaterials.

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Xiaoyu Tang, Northeastern University, Mechanical and Industrial Engineering
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Multiphase flows, involving droplets and/or particles, are ubiquitous in nature and industrial applications, ranging from oil recovery, additive manufacturing, to drug delivery. The major theme in our group is to utilize experimental measurements in multiphase flow systems to unveil fundamental controlling physics and to develop new strategies for applications in energy, environment, and healthcare. In this talk, I will discuss two examples involving droplets and particles. The first topic focuses on the migration of colloidal particles driven by solute concentration gradient, known as diffusiophoresis. Particles can be delivered into dead-end pores via diffusiophoresis, which are otherwise hard or slow to achieve. In addition, utilizing the interaction between solute-emitting particles and surface charge heterogeneity, I will demonstrate a strategy to pattern the particle distribution and assemble particles, which can be exploited in applications such as photonic crystals. In the second part, I will discuss the dynamics of drop impact on liquid films, especially with complex fluids. I will demonstrate how the complex interplay among material properties and impact conditions orchestrate various impact outcomes and discuss scaling analysis of the regime diagram. Our experimental observations and scaling analyses have led to new insights into optimizing operating conditions in various applications such as additive manufacturing.

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Elena Cambria, MIT
9am - 1:30pm | Maxwell Dworkin G115, 33 Oxford Street

Information: Breakfast and lunch will be provided. Gifts will be distributed! The SEAS Lab Connection will host more than 10 SEAS researchers from various SEAS labs. Each representative will have the opportunity to deliver a brief yet engaging lightning or panoramic talk (approximately 7 minutes). These presentations will focus on the respective lab’s research domains, with an emphasis on concluding with potential opportunities for collaboration or highlighting specific expertise needs. In addition, Harvard GRID, CNS, and HCBI representatives will also present their research and fund resources available for the SEAS community. The audience will be open to all SEAS community.

Register for the SEAS Symposium

Jacob Klein, Weizmann Institute of Science, Department of Materials & Interfaces
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Elena Cambria, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: The majority of cancer-related deaths are due to metastasis. The failure to develop efficient anti-metastatic drugs has been attributed to an incomplete understanding of the biological mechanisms that drive metastasis. However, mechanical cues have recently emerged as contributors to tumor development and progression. One of the main physical hallmarks of cancer is elevated extracellular matrix stiffness, which alters tumor cell proliferation, survival, contractility, deformability, and migration. Moreover, recent evidence shows that human cells that change their behavior in response to a certain physical microenvironment have the ability to maintain this behavior even after withdrawal of the original physical stimulus and exposure to a new microenvironment, a concept called “cell mechanical memory”. Bringing these ideas together, we hypothesize that the stiffness-induced biophysical adaptations that are imprinted on tumor cells in the primary tumor microenvironment are retained throughout the metastatic process via mechanical memory, and enhance tumor cell extravasation, survival, and colonization in the metastatic organ. This talk will cover our ongoing investigation of the role of cell mechanical memory in cancer metastasis using microfluidic models of human microvasculature and mouse models. We will also discuss how deciphering mechanisms of mechanical memory formation and retention, including persistent epigenetic changes, can power the discovery of a new class of anti-metastatic drugs.

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Ritu Raman, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Human beings and other biological creatures navigate unpredictable and dynamic environments by combining compliant mechanical actuators (skeletal muscle) with neural control and sensory feedback. Abiotic actuators, by contrast, have yet to match their biological counterparts in their ability to autonomously sense and adapt their form and function to changing environments. We have shown that engineered skeletal muscle actuators, controlled by neuronal networks, can generate force and power functional behaviors such as walking and pumping in a range of untethered robots. These muscle-powered robots are dynamically responsive to mechanical stimuli and are capable of complex functional behaviors like exercise-mediated strengthening and healing in response to damage. Our lab uses engineered bioactuators as a platform to understand neuromuscular architecture and function in physiological and pathological states, restore mobility after disease and damage, and power soft robots. This talk will cover the advantages, challenges, and future directions of understanding and manipulating the *squishy* mechanics of biological motor control.

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Sunghan Ro, Korea Advanced Institute of Science and Technology
1:30pm, Zoom | Jefferson 356, 29 Oxford Street

Abstract: Active matter, encompassing entities such as bird flocks, bacterial swarms, and colloidal particles driven out of equilibrium, exhibits unique characteristics that set it apart from equilibrium systems. Notably, the absence of time-reversal symmetry in active matter leads to phase separation without attraction and the long-range alignment of spins with continuous symmetry in two dimensions, to name a few.

In this seminar, I will explore perturbations in nonequilibrium systems, with a focus on active matter. Specifically, I will examine how macroscopic order in active matter models is affected by quenched disorder or inherent fluctuations in the system. It will be shown that perturbations that are insignificant in equilibrium can have a profound impact on active matter, altering the lower-critical dimension or the stability of macroscopic orders. These results highlight the profound effects of breaking time-reversal symmetry on the physics of macroscopic systems and the methods to examine them in detail.

Bio: Sunghan Ro completed his undergraduate study in physics at the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon, South Korea. He earned his Ph.D. in physics in 2019 from KAIST where he worked under the supervision of Yong Woon Kim. Sunghan then became a postdoc at the Technion-Israel Institute of Technology and worked with Yariv Kafri and Dov Levine. In 2022, he joined Julien Tailleur's group at MIT and is continuing his postdoc research.

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Jue Wang, Purdue University
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Programmable Shape morphing (PSM) devices, a pivotal subset of soft robotics, aspire to achieve programmable, controllable, and reversible transformations reminiscent of biological systems such as octopi and growing plants. They exhibit potential in realms such as augmented and virtual reality (AR/VR) devices, haptics, optical and acoustic metamaterials, and biology. However, morphing into arbitrary surfaces on demand requires a device with a sufficiently large number of actuators and an inverse control strategy.

In this talk, I will explore the integration of machine learning in achieving sophisticated control over complex shape morphing processes as part of my PhD research. Initially, I will delve into how machine learning facilitates the control of actuator arrays under complex coupling in 2D low-profile shape morphing devices. Building on this foundation, I will showcase the development of a 2D PSM device based on an array of ionic actuators. Leveraging the unique driving characteristics of ionic actuators, we have engineered a system that uses passively matrix addressing to independently control N^2 actuators with just 2N inputs. This under-actuation system significantly reduces the number of required control signals, substantially shrinking the controller size and paving the way for wearable device applications. Moving forward, I will discuss the transition from 2D to 3D PSM. Here, I will introduce how we use point cloud data to represent deformations and propose SMNet, a point cloud regression model that maps point cloud data to the inputs of actuator arrays. This approach is versatile across various types of actuator arrays and serves as a universal control framework for 3D PSM devices. Lastly, I will propose a set of performance metrics to evaluate existing studies and offer insights into future research directions. This comprehensive overview aims not only to highlight the innovative application of machine learning for dynamic shape control but also to set the stage for the next generation of PSM devices.

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Hongbo Zhao, Princeton University
1:30pm, Zoom | Jefferson 356, 29 Oxford Street

Abstract: Phase separation underpins a wide range of phenomena from the formation of membraneless intracellular compartments to the behavior of chemically reactive nanoparticles in battery electrodes. Unlike simpler systems like oil and water, however, phase separation in these systems is often complicated by mechanical interactions, nonequilibrium activities, and heterogeneity.

In my talk, I will delve into how I navigated these complexities to uncover new insights into three distinct systems. I will first address liquid-liquid phase separation within chromatin-packed cell nuclei, highlighting how the competition between elastic and capillary forces crucially shapes the structure and mechanics of the chromatin networks. Next, I will share my discovery of novel collective behaviors in active systems such as bacteria and active colloids, due to the interplay between movements along chemical gradients and motility-induced phase separation. Lastly, I'll discuss my work in extracting reaction kinetics and heterogeneity from images of reactive and phase-separating particles in battery electrodes, shedding light on their role in controlling phase separation.

Looking forward, the theory and methodologies I developed for phase separation in fiber networks, active phase separation, and data-driven physics discovery hold immense potential for advancing our understanding of and ability to harness soft and living matter.

Bio: Hongbo Zhao is PBI2 Distinguished Postdoctoral Fellow in the Department of Chemical and Biological Engineering, Department of Mechanical and Aerospace Engineering, and Omenn-Darling Bioengineering Institute at Princeton University, working with Professors Andrej Košmrlj, Cliff Brangwynne, and Sujit Datta. He completed his PhD in Chemical Engineering at MIT advised by Professor Martin Bazant. His PhD research focused on elucidating the physics of energy materials for lithium-ion batteries and data-driven discovery of governing equations from experimental images. Currently, he studies the biophysics of liquid-liquid phase separation in living cells and the collective behavior of active matter, supported by the Princeton Bioengineering Initiative – Innovators Distinguished Postdoctoral Fellowship.

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Jerome Delhommelle, Department of Chemistry, UMass Lowell
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Self-organization and assembly processes are crucial steps in the formation of new phases and materials and can have a dramatic impact on their properties. For instance, the crystal structure, or polymorph, that forms during nucleation often dictates the mechanical and catalytic properties of metal nanoparticles, or the bioavailability of pharmaceutical drugs. Similarly, in biological and living systems, active particles can form intriguing patterns, swarms, or bacterial biofilms. While recent advances in nonequilibrium thermodynamics and statistical physics have started to shed light on the behavior of these systems, a complete understanding of these processes remains elusive. In this talk, I discuss how my group leverages computational materials science and artificial intelligence to shed light on assembly, cooperativity, and emergence in hard, soft, and active matter. I show how AI-guided simulations shed light on assembly pathways in materials and biological systems, and how data science and machine learning provide a new way to accelerate discovery in soft autonomous robotics technology. In this talk, I will discuss how particle-based simulations and artificial intelligence methods can be leveraged to shed light on assembly, cooperativity, and emergence. I will start by examining how entropy can be used as an order parameter, or collective variable, to unravel crystallization processes in interaction-controlled assembly processes. Then, I will examine how data science methods allow for the determination of entropy production and the in-depth analysis of the novel, motility-controlled, phase transitions exhibited by active matter and living systems.

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Dimitrios Krommydas, Lorentz Institute for Theoretical Physics, Leiden University
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Abstract: Collective cell migration in epithelia relies on cell intercalation: a local remodeling of the cellular network that allows neighboring cells to swap their positions. While in common with foams and other passive cellular fluids, intercalation in epithelia crucially depends on active processes. In these processes, the local geometry of the network and the contractile forces generated therein conspire to produce an "avalanche" of remodeling events, which collectively give rise to a vortical flow at the mesoscopic length scale. We formulate a continuum theory of the mechanism driving this process, built upon recent advances towards understanding the hexatic (i.e. 6-fold ordered) structure of epithelial layers. Using a combination of active hydrodynamics and cell-resolved numerical simulations, we demonstrate that cell intercalation takes place via the unbinding of topological defects, naturally initiated by fluctuations and whose late-times dynamics is governed by the interplay between passive attractive forces and active self-propulsion. Our approach sheds light on the structure of the cellular forces driving collective migration in epithelia and provides an explanation of the observed extensile activity of in vitro epithelial layers.

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