About

Heinrich M. Jaeger is the Principal Investigator of the Jaeger Lab, with academic credentials including a Vordiplom from Kiel University and both MS and PhD degrees from the University of Minnesota. His research group focuses on a variety of projects related to granular materials, dense suspensions, nanoparticle sheets, ultrasonic levitation, and soft robotics. The lab investigates complex phenomena such as the dynamics of dense suspensions, material design via particle shape, impact and shocks in granular materials, and robotic aggregates. Jaeger's work encompasses experimental and theoretical studies on multi-component and multi-phase flows, freezing phenomena, acoustic levitation, and strain engineering in nanoparticle membranes. The lab also explores granular metamaterials and particle-laden gels, reflecting a broad interest in the physics and engineering of particulate systems. Jaeger's group includes postdoctoral researchers, graduate students, and undergraduates, indicating an active and diverse research environment. The lab's research contributions span fundamental physics to applied material science, with a strong emphasis on understanding and manipulating the behavior of granular and colloidal systems.

Research topics

• Composite material
• Materials science
• Physics
• Mechanics
• Geology
• Biological system
• Chemistry
• Nanotechnology
• Condensed matter physics

Selected publications

• Studies of granular compaction

  2026-02-19

  book-chapter

  The work reported here is an overview of several studies of the compaction of granular material that we have conducted in our laboratories. We show that external vibrations lead to a slow, essentially logarithmic, approach of the packing density to a final steady-state value. Depending on the initial conditions and the magnitude of the vibration acceleration, the system can either reversibly move between steady-state densities or can become irreversibly trapped into metastable states. We find that the highest packing densities are obtained along the reversible branch. Finally, measurements of the spectrum of density fluctuations around the steady-state values provide a probe of the internal relaxation dynamics of the system and a link to recent thermodynamic theories for the settling of granular material.

  PublisherDOI

• Dicovering the emergent nonlinear dynamics of acoustically levitated cube clusters

  arXiv (Cornell University) · 2026-03-16

  preprintOpen accessSenior author

  The complex behavior of many natural and engineered systems emerges from the interaction of a small number of effective degrees of freedom. Discovering the physical basis of the interactions between these degrees of freedom directly from experimental observations has been a longstanding challenge, particularly with respect to predicting the long-time dynamics of dynamical systems with unknown equations of motion. Here, we introduce a data-driven approach that is able to produce a generative model for the long-time dynamical behavior of systems with a weakly attracting manifold. We apply this method to an experimental dynamical system with two degrees of freedom: acoustically levitated pairs of cube-shaped particles, which cluster by sharing a single edge. In the acoustic trap, the center-of-mass of the cube cluster oscillates vertically about the levitation plane, while also oscillating about their flexible hinge-like connection. Depending on their initial condition, the hinge dynamics evolve about three distinct nonlinear dynamical attractors persisting for hundreds of cycles. In order to capture the underlying physics, we develop a numerical fitting procedure and extract a minimal nonlinear dynamical model that captures both the long-time dynamics of the cluster as well as the convergence onto the dynamical steady state. This dynamical model uncovers the nonlinear, non-reciprocal coupling between the center-of-mass motion and the hinge degree of freedom that stabilizes the dynamical attractors, which we subsequently confirm by independent finite-element methods. Our results demonstrate a novel data-driven method for the discovery of nonlinear models with long-timescale stable predictions.

  PublisherDOI

• Dicovering the emergent nonlinear dynamics of acoustically levitated cube clusters

  ArXiv.org · 2026-03-16

  articleOpen accessSenior author

  The complex behavior of many natural and engineered systems emerges from the interaction of a small number of effective degrees of freedom. Discovering the physical basis of the interactions between these degrees of freedom directly from experimental observations has been a longstanding challenge, particularly with respect to predicting the long-time dynamics of dynamical systems with unknown equations of motion. Here, we introduce a data-driven approach that is able to produce a generative model for the long-time dynamical behavior of systems with a weakly attracting manifold. We apply this method to an experimental dynamical system with two degrees of freedom: acoustically levitated pairs of cube-shaped particles, which cluster by sharing a single edge. In the acoustic trap, the center-of-mass of the cube cluster oscillates vertically about the levitation plane, while also oscillating about their flexible hinge-like connection. Depending on their initial condition, the hinge dynamics evolve about three distinct nonlinear dynamical attractors persisting for hundreds of cycles. In order to capture the underlying physics, we develop a numerical fitting procedure and extract a minimal nonlinear dynamical model that captures both the long-time dynamics of the cluster as well as the convergence onto the dynamical steady state. This dynamical model uncovers the nonlinear, non-reciprocal coupling between the center-of-mass motion and the hinge degree of freedom that stabilizes the dynamical attractors, which we subsequently confirm by independent finite-element methods. Our results demonstrate a novel data-driven method for the discovery of nonlinear models with long-timescale stable predictions.

  PublisherOA PDF

• Shear thickening inside elastic open-cell foams under dynamic compression

  Soft Matter · 2025-01-01 · 4 citations

  articleOpen accessSenior author

  We measure the response of open-cell polyurethane foams filled with a dense suspension of fumed silica particles in polyethylene glycol at compression speeds spanning several orders of magnitude. The gradual compressive stress increase of the composite material indicates the existence of shear rate gradients in the interstitial suspension caused by wide distributions in pore sizes in the disordered foam network. The energy dissipated during compression scales with an effective internal shear rate, allowing for the collapse of three data sets for different pore-size foams. When scaled by this effective shear rate, the most pronounced energy increase coincides with the effective shear rate corresponding to the onset of shear thickening in our bulk suspension. Optical measurements of the radial deformation of the foam network and of the suspension flow under compression provide additional insight into the interaction between shear thickening fluid and foam. This optical data, combined with a simple model of a spring submerged in viscous flow, illustrates the dynamic interaction of viscous drag with foam elasticity as a function of compression rate, and identifies the foam pore size distribution as a critically important model parameter. Taken together, the stress measurements, dissipated energy, and relative motion of the fluid and the foam can be rationalized by knowing the pore size distribution and the average pore size of the foam.

  PublisherOA PDFDOI

• Maxwell’s Relevance to Modern Research in Materials

  Cambridge University Press eBooks · 2025-05-03

  book-chapter1st authorCorresponding
  PublisherDOI

• Dense suspensions as trainable rheological metafluids

  ArXiv.org · 2025-03-12

  preprintOpen accessSenior author

  Memory-forming properties introduce a new paradigm to the design of adaptive materials. In dense suspensions, an adaptive response is enabled by non-Newtonian rheology; however, typical suspensions have little memory, which implies rapid cessation of any adapted behavior. Here we show how multiple adaptive responses can be achieved by designing suspensions where different stress levels trigger different memories. This is enabled by the interplay of interactions based on frictional contact and dynamic chemical bridging. These two interactions lead to novel rheology with several well-delineated shear thinning and thickening regimes, which enable stress-activated memories associated with opposite time-dependent trends. As a result, in response to different stress levels, the suspension can evolve by either softening or stiffening and is trainable, exhibiting targeted viscosity and energy dissipation with repeated low-velocity impact. Such behavior, usually associated with mechanical metamaterials, suggests that dense suspensions with multiple memories can be viewed as trainable rheological metafluids.

  PublisherOA PDFDOI

• Pattern formation in acoustically levitated particle systems with competing near-field interactions

  Physical Review Research · 2025-04-07 · 5 citations

  articleOpen accessSenior author

  Acoustic levitation in air provides a containerless, gravity-free platform for investigating driven many-particle systems with nonconservative interactions and underdamped dynamics. In prior work the interactions among levitated particles were limited to attractive forces from scattered sound and repulsion from hydrodynamic microstreaming. We report on experiments in which contact cohesion provides a third type of interaction. When particle size and separation are both much smaller than the sound wavelength, this interplay of three interactions results in forces that are attractive over several particle diameters, become repulsive at close approach, and are again attractive at contact. In the presence of sound-induced athermal fluctuations that generate particle collisions, the interplay of these three forces enables the formation of particle chains with anisotropic interactions that depend on chain size and shape due to multibody effects. With the control of the kinetic pathways and the strength of the contact cohesion, different patterns can be assembled, from triangular lattices to labyrinthine patterns of chains to lacelike networks of interconnected rings. These results shed light on the multibody character of acoustic interactions and can be utilized to direct the self-assembly of particles.

  PublisherOA PDFDOI

• On the addition of micron-size intruders in a shear-thickening suspension of nanoparticles

  arXiv (Cornell University) · 2025-01-07

  preprintOpen accessSenior author

  This study investigates the rheological behavior of shear-thickening suspensions made of different types of nanoparticles upon the addition of large intruders referred to as granules. The size ratio ranges from 20 to 120. We examine the effects of granule size, volume fraction, and surface properties on shear-thickening characteristics. Starting with a fumed silica suspension exhibiting discontinuous shear thickening (DST) without granules, the addition of granules at different volume fractions, shifts the onset of thickening to lower shear rates. Concomitantly, the strength of the thickening, quantified by the thickening index, decreases, transitioning from DST to continuous shear thickening (CST). Comparison with suspensions of nanosilica spheres reveals a similar trend, suggesting generality across different systems. However, these results contrast with cornstarch-based suspensions, where granule addition enhances thickening. This difference is attributed to the large size ratio studied here: When the granules are much larger than the particles in the interstitial suspension, the granules introduce a spread in the local shear rate and disrupt the particles' ability to form an extended fabric of force chains. The findings highlight the critical role of particle size ratio in determining the rheology of complex suspensions, paving the way for tailoring material properties in industrial and scientific applications.

  PublisherOA PDFDOI

• Strain stiffening due to stretching of entangled particles in random packings of granular materials

  Physical review. E · 2025-02-10 · 2 citations

  articleSenior author

  Stress-strain relations for random packings of entangling chains under triaxial compression can exhibit strain stiffening and sustain stresses several orders-of-magnitude beyond typical granular materials. X-ray tomography reveals the transition to this strong strain stiffening occurs when chains are long enough to entangle an average of about one chain each, which results in system-filling clusters of entangled chains, similar to the Erdös-Rényi model for randomly connected graphs. The number of entanglements is nearly proportional to the area surrounded by entangling particles with an excluded volume effect, thus the existence of system-filling clusters of entanglements can be predicted assuming random particle positions and orientations with an excluded volume effect if the particle shapes in the packing are known. A tendency was found for chain links to stretch when the packing was strained. This suggests that the strength of these packings comes from stretching of the links of chains, but only when the system-filling network of entanglements provides constraints that prevents failure by shear banding, so that particles must be deformed to move further under strain. The slope of the stress-strain relation of a packing can be calculated from a mean-field model consisting of the product of the effective extensional modulus of the chain, packing fraction, probability of stretched links, and the ratio of strain of stretched links to packing strain. In this model, the increasing slope of the stress-strain curve is mainly due to the fraction of stretched links increasing with strain, and assuming the fraction of stretched links is proportional to strain results in a quadratic prediction for the stress-strain curve. The stress-strain model requires as input measurements of the ratio between local particle deformation and global average strain, and the probability of stretching for nonrigid particles, resulting in a quadratic curvature that agrees with experiments within the run-to-run variation (30%). This model for the stress-strain relation is shown to be generalizable to different shapes of entangling particles by applying it to staples, where the packing strength comes from the bending of staples instead of stretching links. The permanent plastic deformation of staples allows measuring statistical quantities from inspection of a poured-out sample after a triaxial compression, without the need for in situ imaging. Both the probability of staples bending and the average bend angle of the arms were found to increase with strain, and these inputs into the model result in a quadratic curvature of the stress-strain that agrees with experiments within the model uncertainties (37%).

  PublisherDOI

• Nonreciprocity and multibody interactions in acoustically levitated particle systems: A three-body problem

  Physical review. E · 2025-07-14 · 2 citations

  articleSenior author

  Pairwise nonreciprocal interactions are known to drive nonequilibrium collective phenomena. However, there also exist interactions that are reciprocal for a pair of objects but break reciprocity through multibody effects. In this case, nonreciprocity emerges spontaneously, without having to use special objects or tailor the interactions. Here, we demonstrate this with three identical spheres acoustically levitated in air that become excited into novel dynamical states through nonreciprocal multibody interactions induced by sound. This three-sphere system allows detailed interrogation of the competition between wave scattering and viscous microstreaming in generating self-organized, dynamic steady states that exhibit collective limit cycles and self-propulsion. Crucially, energy from the acoustic field is redirected to power these dynamics when the configuration of the three particles breaks inversion symmetry. These results introduce a minimal model system for emergent activity and open up new possibilities for self-assembly, where multibody interactions not only determine the resulting structure but also drive spontaneously emerging dynamics.

  PublisherDOI

Recent grants

• Ultrasonically Levitated Granular Matter

  NSF · $473k · 2018–2021

• SGER: Tuning the Conductance of Nanoparticle Arrays

  NSF · $140k · 2007–2010

• Clustering and Charging in Granular Flows

  NSF · $730k · 2013–2019

• Inter-American Materials Collaboration: Chicago-Chile

  NSF · $480k · 2003–2008

• Nanoparticle Monolayer Membranes

  NSF · $420k · 2015–2019

Frequent coauthors

• Sidney R. Nagel

  University of Chicago

  77 shared

• Xiao‐Min Lin

  South China Agricultural University

  58 shared

• Juan Pablo

  Argonne National Laboratory

  44 shared

• Eric Brown

  Southern Connecticut State University

  27 shared

• Endao Han

  Princeton University

  27 shared

• Melody X. Lim

  24 shared

• Ivo R. Peters

  University of Southampton

  24 shared

• Abhinendra Singh

  University of Chicago

  23 shared

Labs

• Heinrich M. Jaeger LabPI

Education

• Ph.D., Physics

  University of Minnesota

  1987

• Other

  University of Chicago

• Other

  Delft Institute for Microelectronics and Submicrontechnology

  1989

Awards & honors

• American Physical Society’s 2026 Leo P. Kadanoff Prize