Muscle-like Supramolecular Polymers: Integrated Motion from Thousands of Molecular Machines (original) (raw)
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Molecular, Supramolecular, and Macromolecular Motors and Artificial Muscles
MRS Bulletin, 2009
Recent developments in chemical synthesis, nanoscale assembly, and molecular-scale measurements enable the extension of the concept of macroscopic machines to the molecular and supramolecular levels. Molecular machines are capable of performing mechanical movements in response to external stimuli. They offer the potential to couple electrical or other forms of energy to mechanical action at the nano- and molecular scales. Working hierarchically and in concert, they can form actuators referred to as artificial muscles, in analogy to biological systems. We describe the principles behind driven motion and assembly at the molecular scale and recent advances in the field of molecular-level electromechanical machines, molecular motors, and artificial muscles. We discuss the challenges and successes in making these assemblies work cooperatively to function at larger scales.
Molecular Motors, Actuators, and Mechanical Devices
Atomically precise manufacturing systems, such as those described in Nanosystems [1], will utilize molecular motors and actuators 1 that drive components to perform useful work. The conversion of electrical and chemical energy into mechanical motion is facilitated by the use of gears, bearings, drive shafts, springs, and so forth, to direct the motion of components and minimize energy losses. Thus, research efforts dedicated to produce these sorts of components are considered to be both a direct pathway in our Roadmap and an enabler of other pathways that can take advantage of these molecular mechanical devices and the fabrication techniques developed to produce them. This section summarizes the state-of-the-art in the construction of these devices and describes their relevance to the Roadmap. Table 3 at the end of this section provides a summary of representative molecular motors, actuators, and mechanical devices.
Linear Artificial Molecular Muscles
Journal of the American Chemical Society, 2005
Two switchable, palindromically constituted bistable rotaxanes have been designed and synthesized with a pair of mechanically mobile rings encircling a single dumbbell. These designs are reminiscent of a "molecular muscle" for the purposes of amplifying and harnessing molecular mechanical motions. The location of the two cyclobis(paraquat-p-phenylene) (CBPQT 4+ ) rings can be controlled to be on either tetrathiafulvalene (TTF) or naphthalene (NP) stations, either chemically ( 1 H NMR spectroscopy) or electrochemically (cyclic voltammetry), such that switching of inter-ring distances from 4.2 to 1.4 nm mimics the contraction and extension of skeletal muscle, albeit on a shorter length scale. Fast scan-rate cyclic voltammetry at low temperatures reveals stepwise oxidations and movements of one-half of the [3]rotaxane and then of the other, a process that appears to be concerted at room temperature. The active form of the bistable [3]rotaxane bears disulfide tethers attached covalently to both of the CBPQT 4+ ring components for the purpose of its self-assembly onto a gold surface. An array of flexible microcantilever beams, each coated on one side with a monolayer of 6 billion of the active bistable [3]rotaxane molecules, undergoes controllable and reversible bending up and down when it is exposed to the synchronous addition of aqueous chemical oxidants and reductants. The beam bending is correlated with flexing of the surfacebound molecular muscles, whereas a monolayer of the dumbbell alone is inactive under the same conditions. This observation supports the hypothesis that the cumulative nanoscale movements within surface-bound "molecular muscles" can be harnessed to perform larger-scale mechanical work. J. AM. CHEM. SOC. 2005, 127, 9745-9759 9 9745 (9) For examples of chemically controllable molecular machines, see (a) Lane, A. S.; Leigh, D. A.; Murphy, A. Ballardini, R.; Balzani, V.; Baxter, I.; Credi, A.; Fyfe, M. C. T.; Gandolfi, M. T.; Gómez-López, M.; Martínez-Díaz, M.-V.; Piersanti, A.; Spencer, N.; Stoddart, J. F.; Venturi, M.; White, A. J. P.; Williams, D. J. Raehm, L.; Sauvage, J.-P.; Divisia-Blohorn, B.; Vidal, P.-L. Inorg. Chem. 2000, 39, 1555-1560. (k) Ballardini, R.; Balzani, V.; Dehaen, W.; Dell'Erba, A. E.; Raymo, F. M.; Stoddart, J. F.; Venturi, M. Eur. J. Org. Chem. 2000, 591-602. (l) Collin, J.-P.; Kern, J.-M.; Raehm, L.; Sauvage, J.-P. Molecular Switches; Feringa, B. L., Ed.; Wiley-VCH: Weinheim, 2000; pp 249-280. (m) Altieri, A.; Gatti, F. G.; Kay, E. R.; Leigh, D. A.; Paolucci, F.; Slawin, A. M. Z.; Wong, J. K. Y. J. Am. Chem. Soc. 2003, 125, 8644-8654. (n) Poleschak, I.; Kern, J.-M.; Sauvage, J.-P. Chem. Commun. 2004, 474-476. For examples of optically controllable molecular machines, see: (o) Ballardini, R.; Balzani, V.; Gandolfi, M. T.; Prodi, L.; Venturi, M.; Philp, D.; Ricketts, H. G.; Stoddart, J. F. Angew. Chem., Int. Ed. Engl. 1993, 32, 1301-1303. (p) Ashton, P. R.; Ballardini, R.; Balzani, V.; Credi, A.; Dress, R.; Ishow, E.; Kocian, O.; Preece, J. A.; Spencer, N.; Stoddart, J. F.; Venturi, M.; Wenger, S. Chem. Eur. J. 2000, 6, 3558-3574. (q) Brouwer, A. M.; Frochot, C.; Gatti, F. G.; Leigh, D. A.; Mottier, L.; Paolucci, F.; Roffia, S.; Wurpel, G. W. Len, S.; Wong, J. K. Y.; Bottari, G.; Altieri, A.; Morales, M. A. F.; Teat, S. J.; Frochot, C.; Leigh, D. A.; Brouwer, A. M.; Zerbetto, F.
Artificial Molecular Motors and Machines: Design Principles and Prototype Systems
Topics in Current Chemistry
A molecular machine can be defined as an assembly of a discrete number of molecular components (that is, a supramolecular structure) designed to perform a function through the mechanical movements of its components, which occur under appropriate external stimulation. Hence, molecular machines contain a motor part, that is a device capable of converting energy into mechanical work. Molecular motors and machines operate via nuclear rearrangements and, like their macroscopic counterparts, are characterized by the kind of energy input supplied to make them work, the manner in which their operation can be monitored, the possibility to repeat the operation at will, i.e., establishing a cyclic process, the time scale needed to complete a cycle of operation, and the performed function. Owing to the progress made in several branches of Chemistry, and to the better understanding of the operation mechanisms of molecular machines of the biological world, it has become possible to design and construct simple prototypes of artificial molecular motors and machines. The extension of the concept of machine to the molecular level is of great interest not only for basic research, but also for the growth of nanoscience and the development of nanotechnology. We will illustrate some basic features and design principles of molecular machines, and we will describe a few recent examples of artificial systems, based on rotaxanes, catenanes and related species, taken from our own research. 2 V. Balzani et al. Keywords Catenane • Electron transfer • Photochemistry • Rotaxane • Supramolecular chemistry Abbreviations AMH ammonium center BPM 4,4-bipyridinium unit CT charge transfer DB24C8 dibenzo[24]crown-8 DON 1,5-dioxynaphthalene unit SCE saturated calomel electrode TTF tetrathiafulvalene unit 1 Basic Principles 1.1
Controlled Rotary Motion in a Monolayer of Molecular Motors
Angewandte Chemie International Edition, 2007
Rotary molecular motors are ubiquitous in natural systems where they are used for diverse tasks including molecular transport, cellular translocation, and ATP synthesis, and are considered key components of future synthetic nanomechanical devices. In many of these systems, such as ATPase or the bacterial flagella motor, immobilization into the cellular membrane allows their rotary action to be harnessed. Attaching biological or synthetic molecular rotary motors to solid substrates is considered to be a key step toward the fabrication of devices that exploit the collective rotational mechanical motion generated by these systems. Although linear synthetic and biological motors have been mounted on surfaces, examples of surface-bound rotary motors are scarce. Preliminary work to this end includes the successful characterization of functioning ATPase while immobilized on quartz and recently, a single example of synthetic rotary molecular motors functioning on gold nanoparticles in solution. Although the latter is a significant step toward future applications, the nanoparticles in solution are still overwhelmed by Brownian rotation and translation, and the motor function might to some extent suffer from excitedstate quenching by the gold, making it difficult to harness work from the system.
Controlling Motion at the Nanoscale: Rise of the Molecular Machines
ACS Nano, 2015
As our understanding and control of intra-and intermolecular interactions evolve, ever more complex molecular systems are synthesized and assembled that are capable of performing work or completing sophisticated tasks at the molecular scale. Commonly referred to as molecular machines, these dynamic systems comprise an astonishingly diverse class of motifs and are designed to respond to a plethora of actuation stimuli. In this Review, we outline the conditions that distinguish simple switches and rotors from machines and draw from a variety of fields to highlight some of the most exciting recent examples of opportunities for driven molecular mechanics. Emphasis is placed on the need for controllable and hierarchical assembly of these molecular components to display measurable effects at the micro-, meso-, and macroscales. As in Nature, this strategy will lead to dramatic amplification of the work performed via the collective action of many machines organized in linear chains, on functionalized surfaces, or in three-dimensional assemblies.
An approach which has been recently introduced to construct microscopic engines is investigated. The main characteristic of the approach is the possibility to determine dynamically the direction of motion of the engines. The engines, which are moving objects on a substrate, are able to move translationally or rotationally and simultaneously perform useful functions such as pulling of a cargo. We discuss an example in which the energy is fed into the engine by changing locally the intrinsic lengths of the moving object. The local changes might be obtained by externally exciting the system. The transformation of the supplied energy into directed motion is through dynamical competition between the intrinsic lengths given by the moving object and the characteristic lengths of the substrate. r
A nano-chemo-mechical actuator based on artifical molecular machines
18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005., 2005
The success of future molecule -driven actuators most likely lies in the development of artificial molecular motors because of their ability to provide large forces from low voltage inputs while also featuring bistable actuation characteristics and molecular design flexibility. With these advantages in mind, we have developed a mechanical device utilizing the force produced from the relative movement of artificial molecular motors -rotaxanes -in conjunction with a hybrid top-down/bottom-up fabrication approach. This process has produced insight into the promise but also the limitations of molecule-driven actuators which inspires redirected efforts for an eventually optimized new class of multiscale mechanical, optical, and medical devices.