Mohsen Shahinpoor*, Ehsan Tabatabaie
Department of Mechanical Engineering, Biomedical Engineering/Advanced Robotics (BEAR) Laboratories, University of Maine, Orono, ME, USA
*Corresponding author: Mohsen Shahinpoor, Department of Mechanical Engineering, Biomedical Engineering/Advanced Robotics (BEAR) Laboratories University of Maine, Orono, ME, USA. Tel: + 12075812143; +12073655967; Email: email@example.com
Received Date: 04 January, 2017; Accepted Date: 18 January, 2018; Published Date: 26 January, 2018
Reported is a new family of Ionic Polymer Metal Composites (IPMCs) sensors and actuators in the form of a loop, made by bending a strip of IPMC around to make an end-to-end cross and form a looped haptic robotic feedback sensor and actuator. The looped cantilever IPMCs is experimentally shown to be capable of bending and twisting as well as sensing characteristics. The sensing characteristics as a soft biomimetic haptic feedback sensor are shown to have great potential for ubiquitous Robot-Human Interactions (RHI) as well as providing haptic force feedback, for example, to surgeons during robotic surgery. Upon various types of deformations, they are shown to generate unique output voltage signal and transient current to be correlated to the actual haptic feedback force. Furthermore, the looped IPMC haptic feedback sensor can enable a new advanced technology in robotic surgery by providing surgeons efficient routines for kinesthetic and softness inquiry of organs and tissues during robotic surgery and yet they can be actuated simultaneously on the fly by a small voltage (4-6 volts) for reconfiguration of looped IPMC feedback sensors for normal grasping and manipulation of bodily organs and tissues. Also, looped IPMC haptic force feedback sensors can be applied as a smart skin for the development of human-like dexterous and soft manipulation.
Ionic Polymer-Metal Composites (IPMCs) belong to a family of electro active polymers that deform spectacularly (in actuation mode) by a small imposed electric field (few kV/m) and also generate electrical fields (sensing and energy harvesting mode) upon physically deforming them (mechanically or by environmental dynamics, such as wind or other natural pulses). They work both in the air and in polar liquids such as water and blood. Ionic Polymer-Metal Composites (IPMCs) are synthetic composite nano materials that display artificial muscle behavior under an applied voltage or an electric field. IPMCs are composed of an ionic polymer like Nafion® or Flemion® whose surfaces are chemically plated or physically coated with conductors such as platinum or gold. Under an applied voltage (1-4 V for typical samples of the size 10mmx40mmx0.2mm), ion migration and redistribution due to the imposed voltage across a strip of IPMC result in bending deformation. If the plated electrodes are arranged in a non-symmetric configuration, the imposed voltage can induce another type of deformations like twisting, rolling, turning, twirling, whirling, and non-symmetric bending deformation. Alternatively, if such deformations are physically applied to the IPMC strips they generate an output voltage signal (few mill volts for typical small samples (5mmx30mmx0.2mm)) as sensors and energy harvesters (Figure 1, Figure 2). They have a force density of about 40 in a cantilever configuration with sizes of 5mmx30mmx0.2mm, meaning that they can generate a tip blocking force of almost 40 times their weight in a cantilever mode. In this case, the weight of the cantilever is around 0.06 gmf based on a density of 2 gm/cm3 for IPMCs which means it can produce a tip blocking force of 2.4 gmf. Another character of these type samples of IPMCs in actuation, sensing, and energy harvesting modes is to have a very broad bandwidth up to kilo HZ and higher. IPMC was introduced in 1998 by Shahinpoor, Bar-Cohen, Xue, Simpson, and Smith [1,2]. However, the original idea of ionic polymer actuators and sensors goes back to 1992- 93 results by Osada, et al. , Oguro, et al. [4-6], Segalman, et al. , Shahinpoor , Doi, et. al  and Adolf, et al. . For manufacturing 3D samples of IPMCs refer to [11-14].
The essential mechanism for both actuation and sensing/energy harvesting capabilities of IPMCs is the migration of cations (Na+, Li+), which are loosely adjoined to the underlying molecular network with anions, towards the cathode electrode and away from the anode electrode due to either an imposed electric field (actuation) or an imposed deformation field (sensing/energy harvesting). (Figure 1) displays the actuation and sensing mechanisms in cantilever strips of IPMCs in a graphical manner. For modeling of IPMC’s actuation, energy harvesting, and sensing see references [15-22].
1.1. IPMC Modeling and Simulation
de Genes and coworkers  presented the first phenomenological theory for sensing and actuation in ionic polymer metal composites. Asoka, et al.,  discussed the bending of polyelectrolyte membrane-platinum composites by electric stimuli and presented a theory on actuation mechanisms in IPMC by considering the electro-osmotic drag term in transport equations. The underlying principles of the Ionic polymeric nano composites’ actuation and sensing capabilities can be described by the standard Onsager formulation using linear irreversible thermodynamics modeling. When static conditions are imposed, a simple description of mechanoelectric effect is possible based upon two forms of transport: ion transport (with a current density, normal to the material) and solvent transport (with a flux, we can assume that this term is water flux). The conjugate forces include the electric field and the pressure gradient, ∇ the resulting equation has the concise form of.
Table 1: Generated Voltage Vs Deformation or Tip Displacement.
Table 2: Generated Voltage Vs Deformation, Flat Front Displacement.
Table 3: Generated Voltage Vs Deformation, Flat Front Displacement.
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2. Shahinpoor M, Y Bar-Cohen, T Xue, J O Simpson, J Smith (1998) Ionic Polymer-Metal Composites (IPMC) As Biomimetic Sensors and ActuatorsArtificial Muscles. Proceedings of SPIE's 5th Annual International Symposium on Smart Structures and Materials 1-5: 3324-3327.
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10. Adolf D, Shahinpoor M., Segalman D. and Witkowski W (1993) Electrically Controlled Polymeric Gel Actuators. US Patent Office 5.
12. Shahinpoor M, Kwang J K, Mehran M (2007) Artificial Muscles: Applications of Advanced Polymeric Nano Composites. CRC Press Taylor & Francis Publishers London SW15 2NU Great Britain 1st Edition.
17. Shahinpoor M (2003) Ionic polymer-conductor composites as biomimetic sensors, robotic actuators and artificial muscles-a review. Electrochimica Acta 48: 2343-2353.
18. M. Shahinpoor and K. J. Kim (2002) Novel Ionic Polymer-Metal Composites Equipped with Physically-Loaded Particulate Electrode as Biomimetic Sensors, Actuators and Artificial Muscles. Actuators and Sensors a Physical 3163: 125-132.
20. Bahramzadeh Y, Shahinpoor M (2011) Charge Modeling of Ionic Polymer-Metal Composites for Dynamic Curvature Sensing. Proceedings of SPIE 18th Annual International Symposium on Smart Structures and Materials 7976: 6-10.
Citation: Shahinpoor M, Tabatabaie E (2018) Soft Biomimetic Robotic Looped Haptic Feedback Sensors. J Robotics Engg and Automation Tech: JREAT-102. DOI: 10.29011/JREAT-102/100002