Papers by Mohsen Shahinpoor
Proceedings of SPIE, May 28, 1999
Miniature, lightweight, miser actuators that operate similar to biological muscles can be used to... more Miniature, lightweight, miser actuators that operate similar to biological muscles can be used to develop robotic devices with unmatched capabilities to impact many technology areas. Electroactive polymers (EAP) offer the potential to producing such actuators and their main attractive feature is their ability to induce relatively large bending or longitudinal strain. Generally, these materials produce a relatively low force and the applications that can be considered at the current state of the art are relatively limited. This reported study is concentrating on the development of effective EAPs and the resultant enabling mechanisms employing their unique characteristics. Several EAP driven mechanisms, which emulate human hand, were developed including a gripper, manipulator arm and surface wiper. The manipulator arm was made of a composite rod with an EAP actuator consisting of a scrolled rope that is activated longitudinally by an electrostatic field. A gripper was made to serve as an end effector and it consisted of multiple bending EAP fingers for grabbing and holding such objects as rocks. An EAP surface wiper was developed to operate like a human finger and to demonstrate the potential to remove dust from optical and IR windows as well as solar cells. These EAP driven devices are taking advantage of the large actuation displacement of these materials but there is need for a significantly greater actuation force capability.
Solar Energy, 2002
Metal hydrides have been investigated for use in a number of solar thermal energy applications, s... more Metal hydrides have been investigated for use in a number of solar thermal energy applications, such as heat regenerators or hydrogen storage technology, but rarely for thermal actuators. Preliminary experimental results from a prototype solar thermal metal hydride actuator, using copper-encapsulated porous metal hydride compacts of LaNi5, indicate that this thermal-mechanical system can produce high specific forces (over 100 (N/g)), with response times on the order of seconds. These operational characteristics, along with features such as being bio-mimetic, compact, operationally safe, lubricationless, noiseless, soft actuating, and environmentally benign, result in an actuator that is ideal for many industrial, space, defense, and biomedical applications. In this paper, we report recent work directed toward predicting and characterizing the performance bounds of the actuator, specically concentrating on elements which might comprise an actuator driven by concentrated solar radiation. A complete solution of the 1D governing heat and mass transfer equations with an ideally selective reactor surface are used to predict bounds on performance in terms of volume flow rates and realistic actuation times. The advantages and disadvantages of the design are discussed from this perspective. The preliminary data show a great potential for these metal hydride actuators to be used for solar thermo-mechanical applications.
Intelligent material systems and structures have become important in recent years due to some pot... more Intelligent material systems and structures have become important in recent years due to some potential engineering applications. Accordingly, based on such materials, structures and their integration with appropriate sensors and actuators, novel applications, useful for a large number of engineering applications have emerged. Here, a mathematical model is presented for the dynamic response of contractile fiber bundles embedded in or around elastic springs that are either linear helical compression springs or hyperelastic springs such as rubber-like materials. The fiber bundle is assumed to consist of a parallel array of contractile fibers made from either contractile polymeric muscles such as polyacrylic acid plus sodium acrylate cross-linked with bisacrylamide (PAAM) or polyacrylonitrile (PAN) fibers. The proposed model considers the electrically or pH-induced contraction of the fibers which may include resistive heating of the fiber in case of shape-memory alloys. The theory then branches out to two different description of such processes for ionic polymeric gel fiber bundles and shape-memory alloy fiber bundles.
Biomacromolecules, Sep 26, 2000
Gel fibers made from polyacrylonitrile (PAN) are known to elongate and contract when immersed in ... more Gel fibers made from polyacrylonitrile (PAN) are known to elongate and contract when immersed in caustic and acidic solutions, respectively. The amount of contraction for these pH-activated fibers is 50% or greater, and the strength of these fibers is shown to be comparable to that of human muscle. Despite these attributes, the need of strong acids and bases for actuation has limited the use of PAN gel fibers as linear actuators or artificial muscles. Increasing the conductivity by depositing platinum on the fibers or combining the fibers with graphite fibers has allowed for electrical activation of artificial muscles containing gel fibers when placed in an electrochemical cell. The electrolysis of water in such a cell produces hydrogen ions at an artificial muscle anode, thus locally decreasing the pH and causing the muscle to contract. Reversing the electric field allows the PAN muscle to elongate. A greater than 40% contraction in artificial muscle length in less than 10 min is observed when it is placed as an electrode in a 10 mM NaCl electrolyte solution and connected to a 10 V power supply. These results indicate potential in developing electrically activated PAN muscles and linear actuators, which would be much more applicable than chemically activated muscles.
Encyclopedia of Biomedical Polymers and Polymeric Biomaterials, 2015
International Journal of Advanced Robotic Systems, Jun 1, 2005
Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Modeling, Simulation and Control of Adaptive Systems, 2015
The aim of the present study was to investigate the potential of using IPMC as a flexible impact ... more The aim of the present study was to investigate the potential of using IPMC as a flexible impact sensor to be used in typical impact protective devices like a protective headgear to estimate the severity level of head impacts. To that end, IPMC strips were embedded into two layers of protective dilatant material and several impact testings were performed. Results of output IPMC voltage and impact acceleration were captured and analyzed. IPMCs appear to present a potential as impact sensors. In so doing, small strips of either Platinum or Gold chemically-plated IPMCs were used. Results of IPMC voltage output and impact accelerations were reported. The results indicate that IPMCs can be used as flexible impact sensors.
American Society of Mechanical Engineers eBooks, 1993
Image Analysis & Stereology, May 1, 1984
World Automation Congress, 2004
Microscale grasping and manipulation has opened new avenues in the field of bio-manipulation and ... more Microscale grasping and manipulation has opened new avenues in the field of bio-manipulation and assembly of MEMS components. Ionic polymer metal composite (IPMC) artificial muscles offer a promising approach for manipulating flexible objects like biological cells. IPMC membranes are electroactive, and therefore bend when a voltage is applied across them. Since they are both flexible and compliant, they do not
Description/Abstract This book presents the papers given at a symposium on the computerized simul... more Description/Abstract This book presents the papers given at a symposium on the computerized simulation and control of manipulators used by robots. Topics considered at the symposium included robot calibration, nonlinear modeling, Kalman filters, flexible ...
Proceedings of SPIE, May 28, 1999
ABSTRACT Ionic polymer metal composites, a subclass of electro-active polymer actuators, offer a ... more ABSTRACT Ionic polymer metal composites, a subclass of electro-active polymer actuators, offer a promising approach to the problem of manipulating small objects, such as those found in micro- electro-mechanical systems (MEMS). While other technological alternatives exist, such as piezo-electric devices, each has at least one characteristic impeding its widespread adoption. A new class of ionic polymer metal composite (IPMC) artificial muscles has been developed at the UNM Artificial Muscles Research Institute (AMRI). IPMC actuators and sensors have been designed, fabricated and successfully tested. These artificial muscles are made from ionic polymeric (polyelectrolyte) gels chemically treated with platinum. IPMCs are three-dimensional networks of cross-linked macromolecular polyelectrolytes with internal electrodes that swell, shrink, bend, and deform in an electric field. Thus, direct computer control of large expansions and contractions of ionic polymeric gel-noble metal composite muscles by means of voltage controller has been achieved. They exhibit large motion sensing and actuation capabilities, can be produced relatively inexpensively, and can be cut arbitrarily small. Since these devices require only a few volts for actuation, they represent a safe alternative to many problems. This paper describes the design of a microgripper which uses both the actuation and sensing capabilities of these artificial muscles.
American Society of Mechanical Engineers eBooks, 1993
Journal of structural mechanics, 1977
ABSTRACT We present an analysis of the Hadamard stability of helical structures and find the suff... more ABSTRACT We present an analysis of the Hadamard stability of helical structures and find the sufficient stability design criteria. We employ a compact 3(n + 1) dimensional vector space for uniform helical structures and arrive at the governing inequality by employing the traditional Hadamard stability criterion.
Smart Materials and Structures, Nov 22, 2011
The 5th World Congress on Biomimetics, Artificial Muscles and Nano-Bio and the 4th International ... more The 5th World Congress on Biomimetics, Artificial Muscles and Nano-Bio and the 4th International Conference on Artificial Muscles were held in Osaka, Japan, 23–27 November 2009. This special section of Smart Materials and Structures is devoted to a selected number of research papers presented at this international conference and congress. Of the 76 or so papers presented at the conference, only 10 papers were finally selected, reviewed and accepted for this special section, following the regular reviewing procedures of the journal. This special section is focused on polymeric artificial muscles, electroactive polymers, multifunctional nanocomposites and their applications. In particular, an electromechanical model for self-sensing ionic polymer–metal composite actuating devices with patterned surface electrodes is presented which discusses the concept of creating self-sensing ionic polymer–metal composite (IPMC) actuating devices with patterned surface electrodes where actuator and sensor elements are separated by a grounded shielding electrode. Eventually, an electromechanical model of the device is also proposed and validated. Following that, there is broad coverage of polytetrahydrofurane–polyethylene oxide–PEDOT conducting interpenetrating polymer networks (IPNs) for high speed actuators. The conducting polymer (poly(3,4-ethylenedioxythiophene)) is incorporated within the IPNs, which are synthesized from polyethylene oxide (PEO)/polytetrahydrofurane (PTHF) networks. PEO/PTHF IPNs are prepared using poly(ethylene glycol) methacrylate and dimethacrylate and hydroxythelechelic PTHF as starting materials. The conducting IPN actuators are prepared by oxidative polymerization of 3,4-ethylenedioxithiophene (EDOT) using FeCl3 as an oxidizing agent within the PEO/PTHF IPN host matrix. Subsequently, giant and reversible magnetorheology of carrageenan/iron oxide magnetic gels are discussed and the effect of magnetic fields on the viscoelastic properties, magnetorheological effect of carrageenan gel containing iron oxide particles are investigated using dynamic viscoelastic measurements under magnetic fields. Furthermore, the relationship between the magnetorheology and the elasticity of magnetic gel is discussed. This special section then covers the characteristics of ionic polymer–metal composite with chemically-doped TiO2 particles to improve the bending performance of ionic polymer–metal composite (IPMC) actuators. This study is mainly focused on the characterization of the physical, electrochemical, and electromechanical properties of TiO2-doped ionic polymer membranes, and IPMCs prepared by the sol–gel method, which results in a uniform distribution of the particles inside the polymer membrane. It was determined that the lifetime of IPMC is strongly dependent on the level of water uptake. This paper is then followed by a presentation on training and shape retention in conducting polymer artificial muscles. Electrochemomechanical deformation (ECMD) of the conducting polymer, polyaniline film, is studied to investigate the behavior of actuation under tensile loads. The ECMD is induced by strains due to insertion of ionic species (cyclic strain) and a creep due to applied loads during the redox cycle. The cyclic strain is enhanced by the experience of high tensile loads, indicating a training effect. The training effect is explained by the enhanced electrochemical activity of the film. The special section then presents a paper on the current status and future prospects of power generators using dielectric elastomers. Electroactive polymer artificial muscle (EPAM), known as 'dielectric elastomer', appears to offer unique capabilities as an actuator and electrical power generator. However, the power output levels of such generators are small and the efficiencies are rather high. For example, electrical energy conversion efficiency of over 70% has been achieved. The ability of EPAM to produce hydrogen fuel for energy storage was also demonstrated. Because the energy conversion principle of EPAM is capacitive in nature, the performance is largely size-independent. Formation of motile assembly of microtubules driven by kinesins is presented next. Microtubule (MT) and kinesin are rail and motor proteins that are involved in various moving events of eukaryotic cells in natural systems. In vitro, the sliding motion of microtubules (rail) can be reproduced on a kinesin (motor protein)-coated surface coupled with adenosine triphosphate (ATP) hydrolysis, which is called a 'motility assay'. Based on this technique, a method is reported for forming MT assemblies by an active self-assembly (AcSA) process, in which MTs are crosslinked during a sliding motion on a kinesin-coated surface. Streptavidin (ST) is employed as glue to crosslink biotin-labeled MTs. This discussion is then followed by a paper on the performances of fast-moving low-voltage electromechanical actuators based on single-walled carbon nanotubes and ionic…
Journal of Materials Chemistry C, 2014
An efficient binary blend of PFO and a novel DA polymer is presented to suppress keto defect site... more An efficient binary blend of PFO and a novel DA polymer is presented to suppress keto defect sites of PFO as well as creating a strong long-lasting blue-color emitting PLED.
Quarterly of Applied Mathematics, Jul 1, 1973
Journal of physics, Aug 1, 2008
This paper addresses the change in mechanical properties of an ionic polymeric metal composite (I... more This paper addresses the change in mechanical properties of an ionic polymeric metal composite (IPMC) microgripper finger when
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Papers by Mohsen Shahinpoor