Electric-Field-Guided Precision Manipulation of Catalytic Nanomotors for Cargo Delivery and Powering Nanoelectromechanical Devices (original) (raw)
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Advanced Functional Materials, 2010
The control over micro-and nanoobjects has attracted great attention in several areas of science, such as nanotechnology and drug delivery. One of the major challenges is to achieve autonomous movement of micro-and nanoscale machines in a fluid and employ them to perform complex tasks such as drug delivery, transport, and assembly of micro-/nano-objects. [1] Richard Feynman in his 1959 speech ''There's Plenty of Room at the Bottom'' envisioned microscopic factories with tiny machines that could perform sophisticated tasks. [2] The dream of manufacturing nanomachines is to mimic biological motors that can convert chemical into mechanical energy and hence develop diverse functions. [3] Some fascinating examples in nature are DNA and RNA polymerase; [4] rotary motors such as ATP synthase; [5] cilia and flagella motors; [6] dyneins, [7] kinesins, [8] and myosins. [9] Catalytic synthetic micro-and nanomotors [10-13] and engines [14,15] are of growing interest because of their high locomotive power and easy control. [16] Several approaches have been focused on the improvement of the catalytic conversion of chemicals (e.g., hydrogen peroxide) into kinetic energy [17-19] and the control over the movement of nanomotors by different sources has been reported. [20] The transport of spherical particles used as cargo [21,22] was recently achieved by either using electrostatic, chemical, or magnetic interactions to attach the cargo. [21,22] Extra functionality has also been given to the cargo (e.g., magnetic properties, chemical modification for electrostatic binding) for loading into the nanomotors. In addition, practical applications require higher towing forces and general mechanisms to bind and unbind different cargo in an easy and controllable way. Recently, rolled-up tubular structures that accumulate gas, which is generated by the catalytic decomposition of a fuel, have been developed. [14] These tubular microjets enhance the power of synthetic micromachines reaching a speed of up to 50 body lengths per second. [15] In this work, we describe the use of rolled-up thin Ti/Fe/Pt films as microbots developing tasks that require full control over their motion and high propulsion power. Maneuvers of self-propelled microbots were wirelessly coordinated by an external magnetic field, which allows the selective manipulation of different microobjects randomly suspended in solution. The physical characteristics of these tubular microbots led to a high propulsion power and allowed more than sixty polymeric cargo-particles to be attached and transferred to a desired location. Moreover, we achieved the selective loading of metallic nanoplates with a ''large'' surface area, their transport and directed assembly into different configurations. These illustrative examples form an attractive concept of
Spatial Control over Catalyst Positioning for Increased Micromotor Efficiency
Gels
Motion is influenced by many different aspects of a micromotor’s design, such as shape, roughness and the type of materials used. When designing a motor, asymmetry is the main requirement to take into account, either in shape or in catalyst distribution. It influences both speed and directionality since it dictates the location of propulsion force. Here, we combine asymmetry in shape and asymmetry in catalyst distribution to study the motion of soft micromotors. A microfluidic method is utilized to generate aqueous double emulsions, which upon UV-exposure form asymmetric microgels. Taking advantage of the flexibility of this method, we fabricated micromotors with homogeneous catalyst distribution throughout the microbead and micromotors with different degrees of catalyst localization within the active site. Spatial control over catalyst positioning is advantageous since less enzyme is needed for the same propulsion speed as the homogeneous system and it provides further confinement ...
ACS Nano, 2012
We describe nanoscale tools in the form of autonomous and remotely guided catalytically self-propelled InGaAs/ GaAs/(Cr)Pt tubes. These rolled-up tubes with diameters in the range of 280À600 nm move in hydrogen peroxide solutions with speeds as high as 180 μm s À1. The effective transfer of chemical energy to translational motion has allowed these tubes to perform useful tasks such as transport of cargo. Furthermore, we observed that, while cylindrically rolled-up tubes move in a straight line, asymmetrically rolled-up tubes move in a corkscrew-like trajectory, allowing these tubes to drill and embed themselves into biomaterials. Our observations suggest that shape and asymmetry can be utilized to direct the motion of catalytic nanotubes and enable mechanized functions at the nanoscale.
Spatial control over catalyst positioning on biodegradable polymeric nanomotors
Nature Communications, 2019
Scientists over the world are inspired by biological nanomotors and try to mimic these complex structures. In recent years multiple nanomotors have been created for various fields, such as biomedical applications or environmental remediation, which require a different design both in terms of size and shape, as well as material properties. So far, only relatively simple designs for synthetic nanomotors have been reported. Herein, we report an approach to create biodegradable polymeric nanomotors with a multivalent design. PEG-PDLLA (poly(ethylene glycol)-b-poly(D,L-lactide)) stomatocytes with azide handles were created that were selectively reduced on the outside surface by TCEP (tris(2-carboxyethyl)phosphine) functionalized beads. Thereby, two different functional handles were created, both on the inner and outer surface of the stomatocytes, providing spatial control for catalyst positioning. Enzymes were coupled on the inside of the stomatocyte to induce motion in the presence of fuel, while fluorophores and other molecules can be attached on the outside.
Chemically Powered Micro- and Nanomotors
Angewandte Chemie International Edition, 2014
Jaideep Katuri received his BSc (Hons) in Physics from Sri Sathya Sai Institute of Higher Learning, Bangalore. He then joined the University of Stuttgart to pursue his Masters in Physics. Currently he is a student assistant at the research group of Samuel Sanchez at the MPI for Intelligent Systems in Stuttgart. His research focuses on studying the behavior and interactions of micromotors at different interfaces.
Catalytic Nanomotors: Autonomous Movement of Striped Nanorods
ChemInform, 2004
Rod-shaped particles, 370 nm in diameter and consisting of 1 µm long Pt and Au segments, move autonomously in aqueous hydrogen peroxide solutions by catalyzing the formation of oxygen at the Pt end. In 2-3% hydrogen peroxide solution, these rods move predominantly along their axis in the direction of the Pt end at speeds of up to 10 body lengths per second. The dimensions of the rods and their speeds are similar to those of multiflagellar bacteria. The force along the rod axis, which is on the order of 10 -14 N, is generated by the oxygen concentration gradient, which in turn produces an interfacial tension force that balances the drag force at steady state. By solving the convection-diffusion equation in the frame of the moving rod, it was found that the interfacial tension force scales approximately as SR 2 γ/µDL, where S is the area-normalized oxygen evolution rate, γ is the liquid-vapor interfacial tension, R is the rod radius, µ is the viscosity, D is the diffusion coefficient of oxygen, and L is the length of the rod. Experiments in ethanol-water solutions confirmed that the velocity depends linearly with the product Sγ, and scaling experiments showed a strong dependence of the velocity on R and L. The direction of motion implies that the gold surface is hydrophobic under the conditions of the experiment. Tapping-mode AFM images of rods in air-saturated water show soft features that are not apparent in images acquired in air. These features are postulated to be nanobubbles, which if present in hydrogen peroxide solutions, would account for the observed direction of motion.
Understanding the Efficiency of Autonomous Nanoand Microscale Motors
JACS, 2013
We analyze the power conversion efficiency of different classes of autonomous nano- and micromotors. For bimetallic catalytic motors that operate by a self-electrophoretic mechanism, there are four stages of energy loss, and together they result in a power conversion efficiency on the order of 10–9. The results of finite element modeling agree well with experimental measurements of the efficiency of catalytic Pt–Au nanorod motors. Modifications of the composition and shape of bimetallic catalytic motors were predicted computationally and found experimentally to lead to higher efficiency. The efficiencies of bubble-propelled catalytic micromotors, magnetically driven flagellar motors, Janus micromotors driven by self-generated thermal gradients, and ultrasonically driven metallic micromotors are also analyzed and discussed.