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Home page > Séminaires > Archives séminaires > Séminaires 2016 > Séminaire MSC. Lundi 6 juin 2016. Robert W. Cohn (University of Louisville, Kentucky) :"High Aspect Ratio Nanostructures : Self Assembly, Ultraflexibility and Implications for Future Nanorobots".

Séminaire MSC. Lundi 6 juin 2016. Robert W. Cohn (University of Louisville, Kentucky) :"High Aspect Ratio Nanostructures : Self Assembly, Ultraflexibility and Implications for Future Nanorobots"

Sauf mention contraire, les séminaires et les soutenances se déroulent à 11h30 en salle 454A du bâtiment Condorcet.


High Aspect Ratio Nanostructures : Self Assembly, Ultraflexibility and Implications for Future Nanorobots

Pr. Robert W. Cohn,

ElectroOptics Research Institute and Nanotechnology Center University of Louisville, Louisville, Kentucky

We ask the question, can dry micron-scale have the same degree of complex cooperative behaviors on solid surfaces as do interacting particles and micro-swimmers in liquids ? Note that nanorobots need not be simply scaled versions of macroscale robots. In fact, scaling may not even be realistic due to capillary forces which dominate over gravity for sub-millimeter objects. However, since mass and volume scale cubically with linear changes in dimension, there are greatly reduced requirements for force generation and energy use at the nanoscale. In trying to envision the form and function of nanorobots we consider possibilities for robots that are composed of extremely flexible, high aspect ratio structures, in which at least one dimension is of nanometer scale, and one or two other dimensions could be many microns, even millimeters in length — resulting in “floppy” structures. Low stiffness enables very low forces, where even radiation pressure ( 3 pN/mw) could produce relatively large displacements. For comparison, single biomolecular motors (e.g. kinesin or flagella) produce around 10 pN of force with velocities of several µm/s in water. In air, where viscosity is 70% smaller than water, velocities approaching mm/s might be possible.

Nanostructures with the requisite mechanical structures for floppy nanorobots not only have been demonstrated, but have been fabricated simply and easily in a matter of seconds by capillary force directed self-assemblies. Structures include polymeric nanofiber air-bridges, trampoline-like membranes, microsphere-beaded nanofibers, and Ag2Ga intermetallic nanoneedles. In addition to reviewing their assembly, AFM force-displacement measurements are presented of these structures in tension, and compressionally and torsionally buckled. The structures, especially in buckled states, can have extremely low stiffnesses such that even motion due to thermal fluctuations is detected relatively easily. Actuation of the buckled structures could be achieved using PDMS loaded with nanomaterials ; e.g., nanotubes, graphene or MoS2, which can be efficiently heated with directed light. Heating produces considerable force through the thermoelastic effect, and this force can be used for continuous translation or to trigger reversible elastic buckling of the nanostructures. Remote stimulation of motion with light, together with temperature, humidity and van der Waals forces, provides possible mechanisms for enabling cooperative behavior between nanorobots.


Contact : Équipe séminaires / Seminar team - Published on / Publié le 14 mai 2016


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