Calendar of MRSEC Events

2024 Events

May 1
Squishy Physics Seminar
Ambika Bajpayee, Northeastern University
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

TBD


April 10
Squishy Physics Seminar
Jeffey Fredberg, Harvard University
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

TBD


April 3
Application Deadline

Science & Cooking for Secondary Science Teachers Program, Harvard University

April 3
Squishy Physics Seminar
Qin (Maggie) Qi, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

TBD


March 20
Squishy Physics Seminar
Xiaoyu Tang, Northeastern University, Mechanical and Industrial Engineering
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Dynamics and manipulation of droplets and particles

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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March 15
SEAS Lab Connection Symposium
Elena Cambria, MIT
9am - 1:30pm | Maxwell Dworkin G115, 33 Oxford Street

SEAS Lab Connection

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

March 13
Squishy Physics Seminar
Jacob Klein, Weizmann Institute of Science, Department of Materials & Interfaces
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Lipid bilayers under transmembrane fields

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

The Role of Tumor Cell Mechanical Memory in Cancer Metastasis

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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February 28
Squishy Physics Seminar
Ritu Raman, MIT
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Soft, Adaptive, Biologically-Powered Actuators

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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February 21
Squishy Physics Special Seminar
Sunghan Ro, Korea Advanced Institute of Science and Technology
1:30pm, Zoom | Jefferson 356, 29 Oxford Street

Perturbation in the Absence of Time-Reversal Symmetry: Lessons from Active Matter

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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February 14
Squishy Physics Seminar
Jue Wang, Purdue University
6 - 7:30pm | Pierce Hall 209, 29 Oxford Street

Revolutionizing Programmable Shape Morphing: Integrating Machine Learning for Inverse Shape Control

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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February 13
Squishy Physics Special Seminar
Hongbo Zhao, Princeton University
1:30pm, Zoom | Jefferson 356, 29 Oxford Street

Dissecting the Complexities of Phase Separation in Living and Engineered Systems

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

Assembly, Cooperativity, and Emergence: An Entropic Viewpoint on Organization Processes in Soft and Active Matter

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

Mesoscopic Theory of Defect Mediated Cell Migration

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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