Itai Cohen

Associate Professor of Physics

508 & C7 Clark Hall
Cornell University
Ithaca, New York 14853

(607) 255-0815
(607) 255-8853 (lab)
itai.cohen@cornell.edu
Cohen Complex Matter Physics Group

B.S., Physics, 1995, University of California at Los Angeles. Ph.D., Physics, 2001, University of Chicago. Post-doctoral Associate, Physics and Division of Engineering and Applied Science, Harvard University, 2001-2005. Assistant Professor, Physics, Cornell University, 2005 - 2011. Associate Professor, Physics, Cornell University, 2011 - present.

Research Areas
My lab studies emergent physical phenomena that arise from interactions between elementary constituents. The systems we study include suspensions of microscopic particles, the macromolecules in biological tissues, and even individuals forming a moshpit. Collectively these constituents collude to make complex materials or systems that are typically out-of-equilibrium and driven beyond their linear response regime. Understanding their mechanical and dynamic behavior often requires the development of new experimental techniques, analysis tools, and theoretical models. Working towards a fundamental understanding of how these systems  respond to various stimuli including shear, electromagnetic fields, acoustical vibrations, and confinement will have a profound effect on our society, ultimately leading to the development of strain stiffening gels for next generation replacement tissues, detergents and pastes whose flow properties can be manipulated, and metamaterials with designed mechanical properties. 

Current Research
We focus on four areas at the forefront of this broad field: I) Complex Fluids –
where the interactions between microscopic particles suspended in a fluid control the material properties; II) Biological tissues – where the organization of cells and  biopolymer networks within the fluid controls tissue properties; III) Mechanical Metamaterials – where the mechanics of the basic building units making up a material can be tuned to control the bulk material response; IV) Biolocomotion – where we study how locomotion in single animals like fruit flies and the collective behavior of dancers at a mosh pit. Understanding the nested physical principles that act on different length scales in such systems remains one of the most challenging and interesting problems in the field of Soft Condensed Matter Physics.

Confocal Rheometers
One of our main goals is to develop instruments and techniques for simultaneous imaging of the material structure and measurement of its flow properties. To this end, we have built shear, compression, and indentation devices, that can be loaded onto a confocal microscope. These devices allow us to simultaneously image the 3-D structure of materials such as a colloidal suspension or biological tissue while measuring the amount of force necessary to deform them. In this way, the link between material structure at the microscopic scale and the material properties at the macroscopic scale can be investigated quantitatively.

Fast Video Image Analysis
We have developed 3D image analysis techniques for extracting insect flight kinematic data from high speed videos and the motion of humans in a crowd. Our main goal has been to automate our image extraction so that significantly larger data sets can be attained and analyzed.

Lab Philosophy
This research is inherently interdisciplinary in nature. To this end, we collaborate with numerous other groups on campus with the aim of producing research results that are greater in scope than the simple cumulative contributions of each individual research group. Nevertheless, my group’s ability to design and build table top experiments that combine custom built force measuring devices with techniques in photolithography, microscopy, confocal microscopy, light scattering, high speed imaging, and image
analysis, allows us to develop novel approaches for investigating these materials and make unique contributions to these studies.

Postdocs
Tsevi Beatus, Marc Miskin, Corinne Henak, Bin Liu

Graduate Students
John Mergo, Jesse Silverberg, Neil Lin, Brian Leahy, Lena Bartell, Sam Whitehead