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Publications

Tunable solidification of cornstarch under impact: How to make someone walking on cornstarch sink

Cornell Affiliated Author(s)
Author
R. Niu
M. Ramaswamy
C. Ness
A. Shetty
Itai Cohen
Abstract

Hundreds of YouTube videos show people running on cornstarch suspensions demonstrating that dense shear thickening suspensions solidify under impact. Such processes are mimicked by impacting and pulling out a plate from the surface of a thickening cornstarch suspension. Here, using both experiments and simulations, we show that applying fast oscillatory shear transverse to the primary impact or extension directions tunes the degree of solidification.

Journal
Science Advances
Date Published
Funding Source
1507607
1509308
1804963
DMR-1507607
DMR-1719875
Research Area
Group (Lab)
Itai Cohen Group

Heterogeneous matrix deposition in human tissue engineered cartilage changes the local shear modulus and resistance to local construct buckling

Cornell Affiliated Author(s)
Author
J.M. Middendorf
C. Dugopolski
S. Kennedy
E. Blahut
Itai Cohen
L.J. Bonassar
Abstract

Human tissue engineered cartilage is a promising solution for focal cartilage defects, but these constructs do not have the same local mechanical properties as native tissue. Most clinically relevant engineered cartilage constructs seed human chondrocytes onto a collagen scaffold, which buckles at low loads and strains. This buckling creates local regions of high strain that could cause cell death and damage the engineered tissue.

Journal
Journal of Biomechanics
Date Published
Funding Source
1719875
DGE-1650441
DMR- 1719875
T0080
Research Area
Group (Lab)
Itai Cohen Group

Embedding orthogonal memories in a colloidal gel through oscillatory shear

Cornell Affiliated Author(s)
Author
E.M. Schwen
M. Ramaswamy
C.-M. Cheng
L. Jan
Itai Cohen
Abstract

It has recently been shown that in a broad class of disordered systems oscillatory shear training can embed memories of specific shear protocols in relevant physical parameters such as the yield strain. These shear protocols can be used to change the physical properties of the system and memories of the protocol can later be "read" out. Here we investigate shear training memories in colloidal gels, which include an attractive interaction and network structure, and discover that such systems can support memories both along and orthogonal to the training flow direction.

Journal
Soft Matter
Date Published
Funding Source
1509308
1748958
Group (Lab)
Itai Cohen Group

Distinct tribological endotypes of pathological human synovial fluid reveal characteristic biomarkers and variation in efficacy of viscosupplementation at reducing local strains in articular cartilage

Cornell Affiliated Author(s)
Author
R.M. Irwin
E. Feeney
C. Secchieri
D. Galesso
Itai Cohen
F. Oliviero
R. Ramonda
L.J. Bonassar
Abstract

Objective: Viscosupplementation has been used for decades to treat mild to moderate osteoarthritis, yet it is unknown if the lubricating function of different pathological synovial fluids (SF) vary, or if they respond differentially to viscosupplementation.

Journal
Osteoarthritis and Cartilage
Date Published
Funding Source
1536463
R01AR071394
P200A150273 J
DOR1790217/17
Research Area
Group (Lab)
Itai Cohen Group

Stress decomposition in LAOS of dense colloidal suspensions

Cornell Affiliated Author(s)
Author
E.Y.X. Ong
M. Ramaswamy
R. Niu
N.Y.C. Lin
A. Shetty
R.N. Zia
G.H. McKinley
Itai Cohen
Abstract

We present a method for stress decomposition to understand the rich interactions present in the large amplitude oscillatory shear (LAOS) of shear-thickening suspensions. This method is rooted in experiments, does not rely on a preexisting rheological model, and is free of any a priori symmetry arguments. The decomposition allows us to extract the hydrodynamic, contact, and Brownian contributions to map out how these stresses evolve over an oscillation cycle.

Journal
Journal of Rheology
Date Published
Funding Source
1509308
1804963
DMR-1507607
Group (Lab)
Itai Cohen Group

Magnetic handshake materials as a scale-invariant platform for programmed self-assembly

Cornell Affiliated Author(s)
Author
R. Niu
C.X. Du
E. Esposito
J. Ng
M.P. Brenner
P.L. McEuen
Itai Cohen
Abstract

Programmable self-assembly of smart, digital, and structurally complex materials from simple components at size scales from the macro to the nano remains a long-standing goal of material science. Here, we introduce a platform based on magnetic encoding of information to drive programmable self-assembly that works across length scales. Our building blocks consist of panels with different patterns of magnetic dipoles that are capable of specific binding.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Funding Source
DMR-1435829
N00014-17-1-3029
1435829
ARL FA8650-19-1-7914
DMR-1719875
Research Area
Group (Lab)
Itai Cohen Group
Paul McEuen Group

Flight of the fruit fly

Cornell Affiliated Author(s)
Author
Itai Cohen
Abstract

There comes a time in each of our lives where we grab a thick section of the morning paper, roll it up and set off to do battle with one of nature's most accomplished aviators-the fly. If, however, instead of swatting we could magnify our view and experience the world in slow motion we would be privy to a world-class ballet full of graceful figure-eight wing strokes, effortless pirouettes, and astonishing acrobatics. After watching such a magnificent display, who among us could destroy this virtuoso? How do flies produce acrobatic maneuvers with such precision?

Journal
Physical Review Fluids
Date Published
Funding Source
1546710
61651-EG
ARO
1056662
DMR award
Research Area
Group (Lab)
Itai Cohen Group

The clot thickens: Autologous and allogeneic fibrin sealants are mechanically equivalent in an ex vivo model of cartilage repair

Cornell Affiliated Author(s)
Author
R.M. Irwin
L.J. Bonassar
Itai Cohen
A.M. Matuska
J. Commins
B. Cole
L.A. Fortier
Abstract

Fibrin sealants are commonly used in cartilage repair surgeries to adhere cells or grafts into a cartilage defect. Both autologous and commercial allogeneic fibrin sealants are used in cartilage repair surgeries, yet there are no studies characterizing and comparing the mechanical properties of fibrin sealants from all-autologous sources.

Journal
PLoS ONE
Date Published
Funding Source
5R01AR071394-02
R01AR071394
1536463
Research Area
Group (Lab)
Itai Cohen Group

Using Acoustic Perturbations to Dynamically Tune Shear Thickening in Colloidal Suspensions

Cornell Affiliated Author(s)
Author
P. Sehgal
M. Ramaswamy
Itai Cohen
B.J. Kirby
Abstract

Colloidal suspensions in industrial processes often exhibit shear thickening that is difficult to control actively. Here, we use piezoelectric transducers to apply acoustic perturbations to dynamically tune the suspension viscosity in the shear-thickening regime. We attribute the mechanism of dethickening to the disruption of shear-induced force chains via perturbations that are large relative to the particle roughness scale.

Journal
Physical Review Letters
Date Published
Funding Source
1U54CA210184-01
NNCI-1542081
1232666
1509308
1804963
Research Area
Group (Lab)
Itai Cohen Group