A Mechanical Actuator Driven Electrochemically by Artificial Molecular Muscles (original) (raw)
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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.
A nanomechanical device based on linear molecular motors
Applied Physics Letters, 2004
An array of microcantilever beams, coated with a self-assembled monolayer of bistable, redox-controllable [3]rotaxane molecules, undergoes controllable and reversible bending when it is exposed to chemical oxidants and reductants. Conversely, beams that are coated with a redox-active but mechanically inert control compound do not display the same bending. A series of control experiments and rational assessments preclude the influence of heat, photothermal effects, and pH variation as potential mechanisms of beam bending. Along with a simple calculation from a force balance diagram, these observations support the hypothesis that the cumulative nanoscale movements within surface-bound "molecular muscles" can be harnessed to perform larger-scale mechanical work.
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.
International Journal of Smart and Nano Materials
Here we review the persisting conceptual discrepancies between different research groups working on artificial muscles based on conducting polymers and other electroactive material. The basic question is if they can be treated as traditional electro-mechanical (physical) actuators driven by electric fields and described by some adaptation of their physical models or if, replicating natural muscles, they are electro-chemo-mechanical actuators driven by electrochemical reaction of the constitutive molecular machines: the polymeric chains. In that case the charge consumed by the reaction will control the volume variation of the muscular material and the motor displacement, following the basic and single Faraday's laws: the charge consumed by the reaction determines the number of exchanged ions and solvent, the film volume variation to lodge/expel them and the amplitude of the movement. Deviations from the linear relationships are due to the osmotic exchange of solvent and to the presence of parallel reactions from the electrolyte, which originate creeping effects. Challenges and limitations are underlined.
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.
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
Molecular springs and muscles: Progress toward augmented electromechanical actuation
Pure and Applied Chemistry, 2006
The application of 3,3'-diphenyl-2,2'-bithiophene as a helical scaffold capable of electrochemical polymerization to yield the corresponding polythiophene is reported. One unique feature of this monomer is its theoretically predicted (DFT) ability to mimic redoxstimulated contraction and expansion. This ability, coupled with traditional electromechanical actuation properties of bulk, redox-active conjugated polymers (CPs), yields a polymeric "molecular muscle" capable of both contraction and expansion.
Artificial nanomachines based on interlocked molecular species: recent advances
Chemical Society Reviews, 2006
The bottom-up construction and operation of nanoscale machines and motors, that is, supramolecular systems wherein the molecular components can be set in motion in a controlled manner for ultimately accomplishing a function, is a topic of great interest in nanoscience and a fascinating challenge of nanotechnology. The field of artificial molecular machines and motors is growing at an astonishing rate and is attracting a great deal of interest. Research in the last decade has shown that species made of interlocked molecular components like rotaxanes, catenanes and related systems are most attractive candidates. In recent times, the evolution of the structural and functional design of such systems has led to the construction and operation of complex molecular machines that, in some cases, are able to do specific tasks.
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.