Dr. Mehran Mojarrad Profile

Dr. Mehran Mojarrad

President & CEO

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Publications (10)

Proceedings Article | 7 June 2000 Paper

Characterization of lightweight electroactive polyelectrolyte composite artificial muscles (CAM) as biomimetic propulsion fins for remote-controlled aquatic vehicles

Mehran Mojarrad

Proceedings Volume 3987, (2000) https://doi.org/10.1117/12.387794

KEYWORDS: Content addressable memory, Polymers, Actuators, Composites, Artificial muscles, Biomimetics, Manufacturing, Data acquisition, Logic, Electrodes

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Proceedings Article | 6 June 1997 Paper

Electrically induced large-amplitude vibration and resonance characteristics on ionic polymeric membrane-metal composites artificial muscles

Mohsen Shahinpoor, Mehran Mojarrad, Karim Salehpoor

Proceedings Volume 3041, (1997) https://doi.org/10.1117/12.275707

KEYWORDS: Composites, Actuators, Polymers, Artificial muscles, Platinum, Ions, Electrodes, Data acquisition, Biomimetics, Ion exchange

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Proceedings Article | 6 June 1997 Paper

Ion-exchange-metal composite sensor films

Mehran Mojarrad, Mohsen Shahinpoor

Proceedings Volume 3042, (1997) https://doi.org/10.1117/12.275724

KEYWORDS: Sensors, Composites, Polymers, Metals, Actuators, Artificial muscles, Platinum, Electrodes, Amplifiers, Intelligent sensors

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In this work sensor films made out of ion-exchange membrane- metal composite polymers developed by treating commercially available ion-exchange membrane polyions with a noble metal such as platinum were investigated. These smart composites exhibit characteristics of both actuators and sensors. Strips of these composites cut in a standard size will undergo large bending displacement when placed in a low electric field. Conversely by bending the composite strip, a voltage can be measured across the thin membrane. The output voltage can then be calibrated for a standard size sensor and correlated to the applied loads or stresses. In this research the sensing capability of these materials were investigated by bending the tip end of a sample and measuring the output voltage. The results were then plotted to get characteristic response of the composite for a given imposed tip displacement. In addition a hysteresis curve for a complete cycle of bending was obtained. The preliminary results showed the existence of linear relationship between output voltage and displacement for all except the last quarter of bending cycle. Unlike strain gages where the output voltage needs to be conditioned and amplified by a factor of 1000 or more, these composite polymer sensors can produce up to millivolt output and sense large deformations in the presence of small amplifier gains of two order of magnitude less than conventional sensors. In addition they can be made in the range of micro to several inches in dimension for various applications. Also they don't face the shortcomings and other limitations associated with bonding of typical strain gages to the work piece. The most important advantage of these composites is the fact that they can be used both as large motion sensors and actuators. This means that by using a simple feedback control scheme and double layers of the composite film, it will be possible to use these composites as self-contained robotic manipulators that don't need sophisticated sensors modules for full integration of intelligence.

Proceedings Article | 14 February 1997 Paper

Some experimental results on the dynamic performance of PAN muscles

Karim Salehpoor, Mohsen Shahinpoor, Mehran Mojarrad

Proceedings Volume 3040, (1997) https://doi.org/10.1117/12.267111

KEYWORDS: Annealing, Distance measurement, Artificial muscles, Ions, Polymers, Lithium, Circulatory system, Sodium, Astatine, Manufacturing

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Proceedings Article | 14 February 1997 Paper

Ion-exchange-metal composite artificial muscle actuator load characterization and modeling

Mehran Mojarrad, Mohsen Shahinpoor

Proceedings Volume 3040, (1997) https://doi.org/10.1117/12.267127

KEYWORDS: Actuators, Composites, Artificial muscles, Polymers, Ions, Platinum, Data acquisition, Polymer thin films, Polymeric actuators, Metals

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Proceedings Article | 14 February 1997 Paper

Linear and platform-type robotic actuators made from ion-exchange membrane-metal composites

Karim Salehpoor, Mohsen Shahinpoor, Mehran Mojarrad

Proceedings Volume 3040, (1997) https://doi.org/10.1117/12.267128

KEYWORDS: Actuators, Composites, Artificial muscles, Polymers, Robotics, Electrodes, Ions, Calibration, Polymeric actuators, Ion exchange

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Proceedings Article | 26 April 1996 Paper

Ion exchange membrane-platinum composites as electrically controllable artificial muscles

Mehran Mojarrad, Mohsen Shahinpoor

Proceedings Volume 2779, (1996) https://doi.org/10.1117/12.237094

KEYWORDS: Composites, Polymers, Artificial muscles, Ion exchange, Platinum, Ions, Actuators, Electrodes, Amplifiers, Arsenic

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Proceedings Article | 9 February 1996 Paper

Noiseless propulsion for swimming robotic structures using polyelectrolyte ion-exchange membrane

Mehran Mojarrad, Mohsen Shahinpoor

Proceedings Volume 2716, (1996) https://doi.org/10.1117/12.232139

KEYWORDS: Robotics, Polymers, Artificial muscles, Composites, Actuators, Motion models, Ions, Ion exchange, Platinum, Mechanics

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In this paper a Nafion^TM polyelectrolyte ion-exchange membrane (IEM) was used as a propulsion fin for robotic swimming structures such as a boat or fish-like object swimming in water or aqueous medium. The Nafion membrane was chemically plated with platinum. The resulting membrane was cut in a strip to resemble a fish-like caudal fin for propulsion. A small function generator circuit was designed and built to produce approximately plus or minus 2.0 V amplitude square wave at varying frequency up to 50 Hz. The circuit board was mounted on a buoyant styrofoam shaped like a boat or a tadpole. The fin was attached to the rear of the boat. By setting the signal frequency to the desired value and thereby setting the frequency of bending oscillation of the membrane, a proportional forward propulsion speed could be obtained. The speed was then measured using a high speed camera. Several theoretical hydrodynamic models were then presented to characterize speed-frequency of the forward motion using available theories on biological fish motion. The results were compared to experimental data which showed close agreement. It turned out that the forward speed of the object was directly proportional to the product of frequency and amplitude of the fin oscillation as in biological fishes. This relation was further simplified by keeping the voltage constant and therefore amplitude of the oscillation. The proportionality constant could be measured for a known geometry of the fin-boat assembly and reactivity of the Nafion membrane used. The system as a whole presented an autonomous robotic swimming structure with frequency modulated propulsion to investigate application of polyelectrolyte hydrogel membranes and their effect on hydrodynamic behavior of an undulating swimming object. As in fishes the thrust force of the robot was generated by evolution of vortices on the sides of the undulating fin. For a constant forward speed, this thrust is equal to the drag force due to geometry and skin friction of the swimming robot. It was observed that regardless of the laminar or turbulent flow pattern around the robot the relation between speed and frequency holds. This research was a proof of concept for investigating fish propulsion known best for undulatory swimming motion, using polyelectrolyte ion-exchange-metal composite membrane.

Proceedings Article | 9 February 1996 Paper

Electrically controllable ionic polymeric gels as adaptive optical lenses

Karim Salehpoor, Mohsen Shahinpoor, Mehran Mojarrad

Proceedings Volume 2716, (1996) https://doi.org/10.1117/12.232167

KEYWORDS: Polymers, Ions, Lenses, Adaptive optics, Liquids, Copper, Glasses, Sodium, Optical properties, Active optics

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Proceedings Article | 9 February 1996 Paper

Electrically controllable artificial PAN muscles

Karim Salehpoor, Mohsen Shahinpoor, Mehran Mojarrad

Proceedings Volume 2716, (1996) https://doi.org/10.1117/12.232131

KEYWORDS: Ions, Polymers, Artificial muscles, Molecules, Dielectrics, Copper, Platinum, Liquids, Electrodes, Sodium

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Artificial muscles made with polyacrylonitrile (PAN) fibers are traditionally activated in electrolytic solution by changing the pH of the solution by the addition of acids and/or bases. This usually consumes a considerable amount of weak acids or bases. Furthermore, the synthetic muscle (PAN) itself has to be impregnated with an acid or a base and must have an appropriate enclosure or provision for waste collection after actuation. This work introduces a method by which the PAN muscle may be elongated or contracted in an electric field. We believe this is the first time that this has been achieved with PAN fibers as artificial muscles. In this new development the PAN muscle is first put in close contact with one of the two platinum wires (electrodes) immersed in an aqueous solution of sodium chloride. Applying an electric voltage between the two wires changes the local acidity of the solution in the regions close to the platinum wires. This is because of the ionization of sodium chloride molecules and the accumulation of Na⁺ and Cl^- ions at the negative and positive electrode sites, respectively. This ion accumulation, in turn, is accompanied by a sharp increase and decrease of the local acidity in regions close to either of the platinum wires, respectively. An artificial muscle, in close contact with the platinum wire, because of the change in the local acidity will contract or expand depending on the polarity of the electric field. This scheme allows the experimenter to use a fixed flexible container of an electrolytic solution whose local pH can be modulated by an imposed electric field while the produced ions are basically trapped to stay in the neighborhood of a given electrode. This method of artificial muscle activation has several advantages. First, the need to use a large quantity of acidic or alkaline solutions is eliminated. Second, the use of a compact PAN muscular system is facilitated for applications in active musculoskeletal structures. Third, the PAN muscles become electrically controllable and therefore the use of such artificial muscles in robotic structures and applications becomes more feasible. A muscle is designed such that it is exposed to either Na⁺ or Cl^- ions effectively. Muscle contraction or expansion characteristics under the effect of the applied electric field are discussed.

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