Characteristics of Ionic Polymer Metal Composite (IPMC) as EMG Sensor

Introduction

IPMC is becoming a suitable popular material among engineers and scientists because of its inherent characteristics of low activation voltage, large bending strain, which can be used as both sensors and actuators. Ionic polymer-metal composites are composed of a per- fluorinated ionomer membrane usually Nafion® or Flemion® plated on both faces with a noble metal such as gold or platinum or nickel and neutralized with a certain quantity of counter ions that provide equity for the electrical charge of anions that are covalently fixed to the backbone ionomer (Sai Nemat Nasser,2006)Ionic polymer-metal composite (IPMC) sensors typically are in the shape of beams, and only provide response to stimuli acting perpendicular to the beam plane (Hong Lei, 2016). For a better review of IPMC as electromechanical sensor, the charge current generation mechanisms due to external pressure in both compression and shear modes can be observed and identified using streaming potential hypothesis. Ionic polymer metal composite (IPMC) has high potential as an artificial muscle which can be driven by a low voltage range between -3 to +3 V. During actuation of an IPMC, an EMG signal can be measured in electric potential which is produced by voluntary contraction of muscle fiber (Mohammad Gudarzi, 2017). The electrolyte that flows in the channels are oriented in different directions within the IPMC, the EDL formed on the metallic phase of the electrode is distributed which results generation of streaming potential. Moreover, the sensing signal is generated in the electrode region. IPMC is similar to piezoelectric sensors which generates potential which is proportional to the applied force (R. K Jain, 2010). The performance of IPMC depends on its dimensions and also the electrode plating⁶whether it is nickel, gold or platinum (Kiwon Park, 2013). IPMC is an EAP material that bends in response to an electrical activation and because of the price efficiency and open-loop control, ionic polymer-metal composite (IPMC) actuators is one of the prime attractions in several biomedical and robotic applications. It is a soft and nontoxic hydrophilic material, making it eligible for application in medical domain. Previously, IPMC Sensor has shown satisfactory results for finger movements, acquiringsenses from neural damaged areas. The biggest advantage to this sensor is, it does not require any external source to work and can be moulded in a simple mechanical structure (Narihiro, 2006). Distributed actuation found in animal muscular systems is one of the main reasons of flexibility, high efficiency, and large energy density (Qingsong, 2018). Thus, the biomimetic actuators or artificial muscles with large displacements have drawn great attention in research and industrial application development. The research work in artificial muscle field, exhibiting the mathematical analysis of a muscle, the software simulation, the comparative study with the natural muscles is implemented¹¹ (Mirna, 2014). Electromyography (EMG) is a process to measure the electric voltage generated due to muscle contraction (Amrutha, 2017). EMG signals can be recorded from muscle using either by intra-muscular EMG (highly accurate detail at muscle fiber level) or surface EMG (basic characteristics i.e. amplitude and shape). Amplitude of surface EMG signals are very low and are easily influenced by external noise, thus to reduce external influences differential configuration is used where the noise is cancelled to some extent owing to the high CMRR of instrumentational amplifier (Beneteau, 2014). Physical signal namely electromyography and skin conductance can be taken into effect¹³for measuring muscle activity and at the same time can be correlated with the precise measuring instrumentation applications (Arturo). Moreover, the working of the EMG which is mainly controlled by the nervous system depends on the muscle physiological properties, which can be further extended and can be correlated with the properties of the IPMC. Primarily the EMG signals are procured from the electrodes directly over the skin, then the signal consisting of all the muscle fiber action potential from underneath the skin, but it fail to detect highly precise values or data coming from the muscle fiber itself, which can be overcome by implementing IPMC sensor and using amplifiers along with it which will be discussed further in this paper (Reaz, 2006; Ambily,2017).Moreover, if compared with IPMC, the EMG sensor are meant to record the electrical signals that emanate the body muscles, and in extension to that IPMC records the electrical manifestation of neuromuscular activation that is being generated during muscle contraction and relaxation (Raut, 2015). Furthermore in detail study it was found that, many muscles can go through several abnormalities such as inflammation of muscle which are quite capable of interrupting the normal output of the EMG Sensor and also can damage it (Hemu, 2015). EMG is an electrical discloser of neuromuscular activation which allows making different physiological process to develop force(Angkoon, 2009). But, they are very sensitive to noise, so a significant quite¹⁵ place is required to work with them (Jonghwa, 2008). So, EMG’s are used, for the examination of the nervous system and to measure the electrical pulse signals, some of its tests includes nerve conduction studies, and muscle needle examination (Mohammad, 2010). After processing of Electromyogram signals it can be used for control signal for a robotic arm (Chris, 2008).Mechanomyography is a method for logging and predicting mechanical activity in the muscle that is contracting (Waqas, 2009). Ionic polymer metal composites (IPMCs) are advanced resources fitting to the grade of ionic electroactive polymers (Barbar, 2004). Low actuation bandwidth of these materials is due to low speed of sound.