Fundamentals of locomotion, turning the empirical to quantitative science
Abstract
The idea of having small, nanoscale objects moving through the surroundings in unidirectional (unlikerandom Brownian particle) and possibly controllable fashion has excited human imagination for a long time. Suffice it to mention Michael Crichton???s science-fiction ???Prey???, or books by Eric Drexler (???Engines ofCreation???, others). Indeed, having such miniature vehicles???there is a plethora of names, such as nanocars, submarines, magnetic swimmers, nano-bots, even in the technical literature???could lead to farreaching and tantalizing applications, from communications and surveillance to medicine (drug delivery or cell-surgery), and to health monitoring and even to structural repair for the Navy.Despite such great appeal, actual achievements are rare, yet the 2016 Nobel Prize in Chemistry wasgiven for molecular motors. Arguably, the molecular motor is now at the same stage as the electrical motor was two centuries ago, circa 1820: scientists-inventors were tinkering with wired spinning wheels and cranks, while barely could one anticipate that it would become fans, electric cars, washer-dryers, pumps, food processors and so forth. Likewise, molecular machines are bound to be ???used in the development of things such as new materials, sensors and energy storage systems???, according to the Nobel Committee press release. For nano-locomotion, theory still remains in its infancy. Although individual considerations and potential surfaces for specific molecules and degrees of freedom are being described, the issues of how to generalize the criteria, scaling or conditional parameter dependencies, remain quite compelling. We propose a theoretical exploration of several archetypal examples, in order to (i) distill the common functional principles, to (ii) determine the individual structural and common physical factors defining the speed (rotation, translation); similarly to (iii) determine specific ??? or general, wherever possible ??? limitations to the energy conversion efficiency; further, to (iv) theoretically explore the architectures required to harness the number of molecular motors into cooperatively producing movement in larger length-scale (and greater force/momentum). For the latter, we will benefit from biomimetic parallels with myosin/kinesin motors operating in muscles, and build the models of how to design mesoscale self-propelling machines. Among specific systems, we will begin from quantum chemistry computations to quantify energy surfaces of the very first Feringa???s C27H20 motor; we will also learn from analysis of energy landscapes of the pre-motor molecules like the rotaxane switch and catenane chain. Parallel to the molecular level, we will explore larger scale well-studied experimentally catalytic swimmers (e.g., Pt|Au), moving in a chemically-active fluid media (a fuel). There are several ways possibly to pose general questions to be pursued. For instance, one can recognize energy (scalar) conversion into directional motion (vector) as a key. This immediately suggests that the symmetry-breaking (choice of direction) ability must be inherent in the operating blackbox structure, molecule or any most simple contraption.With the main tasks being the common principles of molecular motors operation and their collective performance in larger scale autonomously moving machines, we will also revisit our laboratory???s past work on flexo-electricity of 2D materials to see if this electro-mechanical coupling type can be competitive with others, in particular with piezo, and if/how it can be utilized for locomotion. While the focus of the current pilot project is the theoretical modeling and assessment of parametric limits (speed, energy) of molecular scale machines and mesoscale assemblies, we will keep the analysis informed of additional larger challenges of fuel/energy supply (light, electro, chemical) as well as possibilities of control and sensing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 27, 2018
- Source ID
- N000141812609
Entities
People
- Boris I Yakobson
Organizations
- Office of Naval Research
- Rice University
- United States Navy