Chemical Nanomotors

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The aim of this project is develop a new class of microswimmers. Swimming at small length scales is challenging as at low Reynolds numbers the viscous drag is so dominant that any symmetric motion does not lead to propulsion (scallop theorem). Microorganisms have therefore evolved two main swimming strategies. Ciliated microswimmers execute a time asymmetric beat and bacteria rotate a chiral flagellum. Here we propose to build the first fully autonomous microswimmer (no external fields) that moves analogous to a bacterial cell. A new unique fabrication capability that we have developed permits the large scale (>100 billion nanocolloids/hour) growth of complex 3D shapes including inorganic nanohelices that can contain several materials, which in turn can be addressed via chemical functionalization. Our fabrication has a precision of 20 nm, and the size range is between 40 nm and 4 microns.In addition to the fabrication capabilities, we have access to and experience with the ATPase. During the hydrolysis of ATP the enzyme rotates. ATPase will be the rotary engine of the proposed microswimmer. Our enzyme is genetically modified so that on one side we will couple a body that functions as a counter-weight (e.g. a particle) and on the opposite end will couple a suitable flagellum that we fabricate with the aforementioned scheme. Several orthogonal coupling chemistries are employed to assemble this hybrid swimmer. SEM and TEM imaging, including in liquid, will be used to verify the construction of the swimmer. The use of fluorescent labels will allow us to use both fluorescence imaging as well as differential dynamic microscopy, which can be used for ensemble measurements. This project will allow us to build an artificial bio-hybrid swimmer that can operate in water. We can address interesting questions of low Reynolds number hydrodynamics as we can reduce the size to regimes where continuum hydrodynamics still holds, but where Brownian effects will become important. The dependence on the chemical fuel ATP serves as a control and permits studies of efficiency for different loads. In addition to swimming in 3D, we can also anchor the enzymes in large numbers on a surface. At one end the enzymes will be attached to the surface at the other end we can couple an inorganic nanostructure to the enzyme. This will allow us to study the collective behavior of an array of chemically-powered propellers. Finally, our fabrication scheme is so general that we can use it to grow large numbers of complex shaped colloids with more functionality and more complex shapes than what has been possible thus far and thus realize an array of new microswimmers that can be driven by chemical, thermal, diffusio-, or photophoretic means. These we will fabricate and make available to other groups within the SPP. Combined multi-functional and steerable micro- and nanoswimmers should be realizable with the unique nanotechnological capabilities at our disposal.