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My lab studies matter in motion. In many cases we are fascinated with emergent physical phenomena that arise from interactions between the individual constituents be they colloidal particles, polymeric strands, neurons, or individuals. Often, these complex phenomena involve materials driven out-of-equilibrium and beyond their linear response regime. Understanding their behavior often requires the development of new experimental techniques, analysis tools, and theoretical models.
- Applied and Engineering Physics
- Mechanical Engineering
- Cornell Center for Materials Research (CCMR)
- Laboratory of Atomic and Solid State Physics (LASSP)
We focus on a number of areas at the forefront of this broad field: I) Complex Fluids – where the interactions between microscopic particles suspended in a fluid control material properties; II) Biological tissues – where the organization of cells and biopolymer networks controls tissue properties; III) Biolocomotion – where emergent properties of neural networks control mechanisms needed to maintain flapping flight; IV) Origami materials – where folding tailors the shape, mechanics, and transformations of the resulting materials; V) Magnetic Handshake Materials – where we build microscopic robots too small to see with the naked eye that are controlled by computer chips that dictate the local interactions; and VI) Magnetic Handshake Materials – where we use magnetic dipole patterns on microscopic particles to dictate their interactions with one another. 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.
Moreover, in each case, working towards a fundamental understanding of the phenomena we study has the potential to profoundly affect society. Our colloidal studies are uncovering new methods for tuning the flow properties of thickening suspensions that will be used to create the next generation flexible spacesuits, 3D printing pastes, and fluids for vehicle traction control. Our work on cartilage is elucidating the location dependent mechanical properties needed for 3D printing replacement tissues. Our work on the flight of insects is shedding light on methods used by animals to distribute control throughout their bodies as well as the neural circuits used in these controllers. Learning how to self-fold atomically thin sheets is a pathway to self-assembly of nanoscale machines. Our work on microscopic robotics may someday revolutionize surgery on the microscopic scale. Finally, our work on magnetic handshake materials is a powerful self-assembly system at the microscale which may lead to new materials and even the emergence of life like processes such as self-replication and autocatalysis.
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.
To study insect flight, we 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.
To study dense suspensions of colloidal particles we often use 3D confocal microscopy. Using these images we invented techniques for measuring forces at the single particle scale as well as methods for locating particle positions and determining their radii down with nm scale precision.
We are heavy users of the Cornell Nanofabrication Facility, arguably the best facility of its class on any academic campus. We use the CNF to build our microscopic robots and fabricate our magnetic handshake materials building blocks.
This research is inherently interdisciplinary in nature. Our group freely traverses past what would be considered the traditional boundaries of Physics in pursuit of the most interesting and highest impact scientific questions. 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, 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.
Qingkun Liu, Itay Griniasty
Sam Whitehead, Meera Ramaswamy, Eric Schwen, Baris Bircan, Yunus Kinkhabwala, Thomas Wyse Jackson, Han Kehng Teoh, Kemper Ludlow, Jingyang Zheng, Edward Yong Xi Ong, Wei Wang, Hanyu Zhang
- Miskin, M.Z., Cortese, A.J., Dorsey, K., Esposito, E.P., Reynolds, M.F., Liu, Q., Cao, M., Muller, D.A., McEuen, P.L. and Cohen, I., 2020. Electronically integrated, mass-manufactured, microscopic robots. Nature, 584(7822), pp.557-561.
- Niu, Ran, Meera Ramaswamy, Christopher Ness, Abhishek Shetty, and Itai Cohen. "Tunable solidification of cornstarch under impact: How to make someone walking on cornstarch sink." Science Advances 6, no. 19 (2020): eaay6661.
- Cohen, Itai, and Melanie Dreyer-Lude. Finding Your Research Voice: Story Telling and Theatre Skills for Bringing Your Presentation to Life. Springer Nature, 2020.
- Niu, Ran, Chrisy Xiyu Du, Edward Esposito, Jakin Ng, Michael P. Brenner, Paul L. McEuen, and Itai Cohen. "Magnetic handshake materials as a scale-invariant platform for programmed self-assembly." Proceedings of the National Academy of Sciences 116, no. 49 (2019): 24402-24407.
- Miskin, Marc Z., Kyle J. Dorsey, Baris Bircan, Yimo Han, David A. Muller, Paul L. McEuen, and Itai Cohen. "Graphene-based bimorphs for micron-sized, autonomous origami machines." Proceedings of the National Academy of Sciences 115, no. 3 (2018): 466-470.
- Pikul, J. H., S. Li, H. Bai, R. T. Hanlon, I. Cohen, and R. F. Shepherd. "Stretchable surfaces with programmable 3D texture morphing for synthetic camouflaging skins." Science 358, no. 6360 (2017): 210-214.
- Lin, Neil YC, Matthew Bierbaum, Peter Schall, James P. Sethna, and Itai Cohen. "Measuring nonlinear stresses generated by defects in 3D colloidal crystals." Nature Materials (2016).
- Tunable Shear Thickening Proceedings of the National Academy of Sciences (2016).
- Silverberg, Jesse L., Aliyah R. Barrett, Moumita Das, Poul B. Petersen, Lawrence J. Bonassar, and Itai Cohen. "Structure-function relations and rigidity percolation in the shear properties of articular cartilage." Biophysical journal 107, no. 7 (2014): 1721-1730.
- Silverberg, Jesse L., Arthur A. Evans, Lauren McLeod, Ryan C. Hayward, Thomas Hull, Christian D. Santangelo, and Itai Cohen. "Using origami design principles to fold reprogrammable mechanical metamaterials." Science 345, no. 6197 (2014): 647-650.
- Cheng, Xiang, Jonathan H. McCoy, Jacob N. Israelachvili, and Itai Cohen. "Imaging the microscopic structure of shear thinning and thickening colloidal suspensions." Science 333, no. 6047 (2011): 1276-1279.
- Ristroph, Leif, Attila J. Bergou, Gunnar Ristroph, Katherine Coumes, Gordon J. Berman, John Guckenheimer, Z. Jane Wang, and Itai Cohen. "Discovering the flight autostabilizer of fruit flies by inducing aerial stumbles." Proceedings of the National Academy of Sciences 107, no. 11 (2010): 4820-4824.