Faculty Publications
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Item Influences of dielectric and conductive fillers on dielectric and mechanical properties of solid silicone rubber composites(Springer London, 2019) Manohar Shankar, B.S.; Kulkarni, S.M.Dielectric elastomers are materials being used for electromechanical transduction applications. Their electromechanical response depends on permittivity, Young’s modulus and electric breakdown strength. A factor that limits its application is high operating voltages that can be reduced through improvement in permittivity. One of the methods is by incorporating high permittivity fillers into polymer matrix to obtain dielectric–dielectric composites (DDC).These composites show high permittivity at the cost of reduced flexibility. An alternative solution is development of composites by incorporating organic or inorganic conductive fillers into polymer matrix. These composites show high permittivity with high dielectric loss and low breakdown strength. To overcome both the above limitations both dielectric and conductive fillers are incorporated into dielectric polymer matrix to obtain conductor–dielectric composites (CDC). In this study, high temperature vulcanized solid silicone rubber as matrix has been used to prepare DDC composites with barium titanate (BT) filler and CDC composites with both BT as dielectric and ketjenblack as conductive fillers, using Taguchi design of experiments. The effect of factors such as amount of fillers and curing agent, mixing time in roll mill and curing temperature on the dielectric and mechanical properties are reported. Lichtenecker model predicts the permittivity of the DDC composite more accurately. For the CDC composites permittivity increased by 390%, effective resistivity decreased by 80%, Young’s modulus increased by 368% and Shore A hardness increased by 90% as compared to those of reference matrix. Important interaction effects are observed among both the fillers that are uniformly dispersed without any aggregation. © 2019, Iran Polymer and Petrochemical Institute.Item Processing and investigation of mechanical characteristics on the polydimethylsiloxane/carbon black composites(Institute of Physics Publishing helen.craven@iop.org, 2019) Hiremath, S.; Sangamesh, R.; Kulkarni, S.M.The mechanical adaptability of elastomers has enormous potential in fields such as energy harvesting, micro electro mechanical system (MEMS), sensor, and actuator. A significant issue is to improve the mechanical features of the elastomeric base material by incorporating an appropriate filler. The elastomer Polydimethylsiloxane (PDMS) is reinforced with carbon black (CB) particles that affect mechanical characteristics (Tensile strength, compressive strength, tear strength, etc) and that have a critical impact on the efficiency of the device. The current research examines the mechanical characteristics of plain PDMS with a concentration of CB filler between 5% and 25%. A solution casting method is used to prepare the composite substrate and investigate the impacts of CB loading performance on tensile, compression, tear, and hardness testing. The outcome shows an improvement in mechanical characteristics due to CB material for Young's module as 1.64-3.84 MPa, ultimate tensile strength as 1.86-4.8 MPa, 3.67-4.81 MPa compressive module with the same compressive strength up to 40 percent strain. The tear strength of the PDMS/CB composites is improved by ?111 percent at 25 percent volume fraction of the CB. The composite hardness of PDMS/CB increases by about 30 percent of the plain PDMS material. Continuing with this, Additional mechanical characteristics of PDMS/CB composites on shear and bulk modules are reported. © 2019 IOP Publishing Ltd.Item Influence of conductive and dielectric fillers on the relaxation of solid silicone rubber composites(Institute of Physics Publishing helen.craven@iop.org, 2019) Manohar Shankar, B.S.; Hiremath, S.; Kulkarni, S.M.Flexible dielectrics possessing high permittivity and low loss are desirable for many electromechanical transduction applications. Solid silicone rubber composites are promising materials for electromechanical applications. These composites are fabricated using high-temperature vulcanization process, with various amounts of conductive, dielectric and conductor-dielectric filler and processing parameters. Dielectric and conductivity relaxations of these composites are investigated using dielectric spectroscopy in the 20 Hz-2 MHz frequency range at room temperature. Dielectric relaxations of dielectric filler composites show different behaviour compared to conductive and conductive - dielectric filler composites even with the same filler loading. All composites show increased permittivity at lower frequencies. The maximum permittivity of 46, 5.8 and 46 at 20 Hz was attained for the conductive, dielectric and conductive-dielectric composites respectively at similar filler loadings. The composites follow the AC universality law with exponents in the range of 0.82 to 1.02. The conductive filler is more reinforcing than dielectric filler as seen from the variation of Young's modulus with filler type. Uniform dispersion of fillers is observed for all the three composites. © 2019 IOP Publishing Ltd.Item Experimental investigation on performance of disposable micropump with retrofit piezo stack actuator for biomedical application(Springer Verlag service@springer.de, 2019) Mohith, S.; Karanth P, P.N.; Kulkarni, S.M.Extensive researches are being conducted to develop miniaturized pumping systems to fulfill the need for accurate delivery of fluids at required rates, particularly in the biomedical field. This paper presents the design, fabrication, and testing of novel valveless micropump actuated through an amplified piezo actuator. The proposed model of the micropump pump has the unique feature of a disposable chamber and employs low-cost polymeric materials, conventional molding and machining operations for fabrication. The disposable part of the pump consists of a laser-cut pump chamber with nozzle/diffuser made of Polymethyl methacrylate (PMMA) and conventionally molded silicone rubber diaphragm. The retrofit part includes the amplified piezo actuator and support structures build from PMMA. Systematic characterization of the pump was carried with water and blood mimicking fluid to understand the effect of operating parameters such as driving frequency and actuation voltage on flow rate and back pressure of the micropump. Experimental results show that the proposed design was capable of pumping 3.3–3.4 ml/min of dye solution and 1.7–1.75 ml/min of blood mimicking fluid at a driving frequency of 5 Hz and actuation voltage of 150 V. The corresponding computed volume resolution/stroke of the pump was found to about 5.75 µl and 11.25 µl of blood mimicking fluid and dye solution, respectively. The proposed pump was found to work effectively against a maximum back pressure of 156 Pa with blood mimicking fluid and 250 Pa with the dye solution as the working fluid under the same operating condition of 5 Hz and 150 V. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Item Performance analysis of valveless micropump with disposable chamber actuated through Amplified Piezo Actuator (APA) for biomedical application(Elsevier Ltd, 2020) Mohith, M.; Karanth P, N.; Kulkarni, S.M.The precise manipulation of fluid through pumping systems has been the technological challenge in microfluidic applications. The biomedical applications call for precise and accurate delivery of fluid through miniaturized pumping systems. This paper presents a novel valveless micropump for biomedical applications operated by the Amplified Piezo Actuator. Integrating the disposable chamber and reusable actuator with the proposed micropump allows the actuator to be reused and eliminates the possibility of infection or contagion. The micropump was fabricated using low-cost polymeric materials like Polymethylmethacrylate (PMMA), Silicone rubber through CNC milling, Laser Cutting, conventional moulding operation. The micropump chamber, nozzle/diffusers, and a bossed diaphragm constituted disposable part and Amplified Piezo Actuator with structural support formed the reusable part of the micropump. The bossed diaphragm of the pump chamber consists of a central cylindrical protrusion to reduce the force of adhesion on the diaphragm and transmit force required for micropump actuation. A theoretical analysis was performed to assess the effect of diaphragm thickness and the bossed region on the effective stiffness of the diaphragm, which in turn influences the deflection achieved. Besides, an analytical approach has been presented to address the effect of adhesive force on the diaphragm surface due to the residual fluid and chamber depth. The experimental characterization of the micropump was carried out to determine the optimal performance parameters with water, fluids mimicking blood plasma, and whole blood. Based on the experimental results, the pumping rate and head developed by the micropump have been significantly affected by factors such as bossed ratio, diaphragm thickness, depth of the micropump chamber, and viscosity of the fluid. The optimum configuration of the micropump cosidered silicone rubber diaphragm with thickness of 0.20 mm having a bossed ratio of 0.33 and a chamber depth of 1.25 mm. With the optimal operating parameters of 150 V sinusoidal input of frequency 5 Hz, the proposed micropump was capable of delivering 7.192 ml/min, 6.108 ml/min, and 5.013 ml/min of water and blood plasma, whole blood mimicking fluid with the maximum backpressure of 294.00 Pa, 226.243 Pa, and 204.048 Pa respectively. The corresponding resolution, i.e., pumping volume/stroke of the micropump was about 23.972 µl, 20.358 µl, and 16.708 µl, respectively. © 2020 Elsevier LtdItem Photomechanical actuation of polydimethylsiloxane/carbon black nanocomposite(Institution of Engineering and Technology jbristow@theiet.org, 2020) Hiremath, S.; Kulkarni, S.M.Materials such as carbon black (CB), carbon nanotube, graphene, etc. have been found to deform on exposure to the light source. Introducing these materials into polymers could convert them to photo-responsive composites. This is demonstrated by the experiment in which polydimethylsiloxane (PDMS) polymer containing CB nanofiller composites is prepared, and its photomechanical actuation from exposure to IR light source is recorded using a laser displacement sensor. The particle size analysis reveals the size of the CB, which is verified by the dynamic light scattering method. The UV-vis-IR spectrophotometer study shows that an increase in the light absorbance capacity of nanocomposites compared to the plain polymer. The PDMS/CB nanocomposite beam exhibited a significant deformation compared to plain PDMS. Deformation of the order of 10-11 mm is observed for a given IR source. The deformation found to have good repeatability but with some thermal hysteresis in cyclic actuation and de-actuation. © 2020 Institution of Engineering and Technology. All rights reserved.Item PDMS–ZnO flexible piezoelectric composites for measurement of muscle activity(Springer, 2020) Jugade, S.S.; Kulkarni, S.M.Measurement of muscle activity is important for muscle health monitoring, biomechanics studies, developing prosthesis, etc. This article describes a flexible piezoelectric composite material as a sensing element for measuring muscle activity. The developed piezoelectric material is a composite of polydimethylsiloxane and zinc oxide, and exists in monolayer and bilayer configurations. To test the piezoelectric properties in bending mode, a composite patch is attached to a cantilever beam setup. Peak sinusoidal voltage generated from the composite material due to the vibrating cantilever is found to be highest (1.5 V) for bilayer configuration with 30 wt% ZnO. For testing in axial mode, the peak output voltage from the material due to an impulse load is maximum (0.9 V) for the monolayer configuration of the composite with 30 wt% ZnO. The sensor consisting of a bilayer composite patch is wrapped around a specific muscle to measure its activity. The change in output voltage from the sensor is measured for increasing load and is then mapped to the corresponding value of elastic modulus of the muscle measured using a durometer. The sensitivity of the muscle activity measurement for biceps brachii and flexor carpi is found to be 3.826 and 1.245 V MPa?1, respectively. © 2020, Indian Academy of Sciences.Item Investigation on dielectric properties of PDMS based nanocomposites(Elsevier B.V., 2021) Hiremath, S.; Kevin, A.M.; Manohar, S.B.S.; Kulkarni, S.M.Polymer nanocomposites have recently been used in applications for energy storage, sensors, and actuators. The polymer materials are gaining dielectric properties such as dielectric permittivity, electrical modulus, and conductivity. In the present study, nanocomposite material is prepared by a solution cast method incorporating carbon black particles into polydimethylsiloxane. The dielectric properties of PDMS/CB nanocomposites are investigated over broad frequency using an impedance analyzer. The polymer nanocomposite's dielectric permittivity is evaluated using the various empirical models available in the literature. Compared with other methods the Wiener model is very similar to the experimental findings. For the frequency range of 100 Hz-100kHz, the frequency-dependent and independent dielectric response was observed. Nanocomposite dielectric permittivity is improved marginally with the reinforcement of carbon black particles. The nanocomposite dielectric loss moves to the higher frequency, although the losses are small. It is proved that electrical modulus can reduce the effect of polarization of electrodes. Nanocomposite AC conductivity exhibits strong frequency dependence particularly in the higher frequency region of the vicinity. This behavior obeys the power law at critical frequency, which reveals the process of relaxing conductivity. The PDMS/CB nanocomposites power-law exponent is within a range of 0.48–0.57. Eventually, empirical and experimental inspections are the basis framework for designing electronic devices based on polymers. © 2020 Elsevier B.V.Item Progression and characterization of polydimethylsiloxane-carbon black nanocomposites for photothermal actuator applications(Elsevier B.V., 2021) Hiremath, S.; H, S.M.; Kulkarni, S.M.The new development of polymer-based actuators triggers the progress of nanocomposites. Polymer materials are currently used in sensors, microfluidic devices, electrical and thermal actuators, and energy harvesting applications due to ease of availability, excellent tolerable properties, and customizable properties. The polymer-based nanocomposite can be driven by various stimuli, which is the actuator's emerging field. Thus, photothermal actuation is a thurst area of research transforming light energy into mechanical energy through the polymer material. The photo-responsive material can be prepared and tested for photo-actuation by incorporating the nanoparticles into the polymer. The present work focuses on developing polydimethylsiloxane (PDMS) and carbon black (CB) nanocomposite. The objective here is to investigate the photothermal actuator's performance by illuminating the infrared (IR) light source and studying its most influential characteristics, such as absorbance, thermal conductivity, and the thermal expansion coefficient. The PDMS / CB nanocomposite absorbs the IR light and then increases temperature, which is finally transformed into a beam deflection. Responses are measured as a result of time deflection using the Laser displacement sensor. It is noted that the deflection of the nanocomposite beam is linearly increased during illumination with light while it is exponentially decreasing when the light is turned off. The proposed polymer nanocomposite is approximately deflected by 9 mm in the duration of 16 s duration. Furthermore, the experimental deflection of the photothermal actuator is very close to theoretical results. The nanocomposite PDMS / CB reveals that there is an increase in absorbance by increasing the filler content. The nanocomposite conductivity is 35.2 % higher than the base material. As well, the thermal expansion coefficient decreases with an increase in carbon black content. The photothermal actuator's development is an ongoing process in which the material parameter, actuator geometry, and many more are modified. As a result, the photothermal bending performed can provide a means for various light-driven applications. © 2020 Elsevier B.V.Item Effect of ketjenblack and barium titanate on the piezoresistive behaviour of silicone rubber particulate composites(IOP Publishing Ltd, 2021) Manohar Shankar, B.S.; Hiremath, H.; Kulkarni, S.M.In the present study, silicone rubber reinforced with ketjenblack and barium titanate were fabricated using high temperature compression molding method. These particulate composites are characterized for piezoresistive sensitivity. Ketjenblack and barium titanate are the conducting and dielectric fillers in the high temperature vulcanized silicone rubber matrix. The effects of ketjenblack and barium titanate fillers, filler loading, amount of curing agent, curing temperature and mixing time on the piezoresistive properties of these composites were investigated. The piezoresistive sensitivity recorded maximum values of 3.7(10-3) (kPa)-1 for dielectric and dielectric-conductive composites. The linear variation of normalized resistance change was observed for change in pressure up to 20 kPa. The dielectric composite sensitivity increases with reduction in dielectric filler and curing agent loadings, increasing with mixing time and curing temperature. The piezoresistive sensitivity for dielectricconductive composites depends on ketjenblack and barium titanate filler loading. These composites demonstrate interaction effects among the factors. © 2021 The Author(s). Published by IOP Publishing Ltd.