Faculty Publications

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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.
Performance comparison of piezo actuated valveless micropump with central excitation and annular excitation for biomedical applications
(IOP Publishing Ltd, 2021) Mohith, S.; Karanth P, N.; Kulkarni, S.M.; Desai, V.; Patil, S.S.
In recent years, microfluidic devices, particularly micropumps, are extensively utilized in biomedical applications. The micropump used in biomedical applications needs to possess precise delivery of fluids at requires rate and pressure. The present work proposes a valveless mechanical micropump with a disposable chamber integrated with a novel concept of annular excitation of the diaphragm to fulfil the need for precise delivery of fluids in biomedical applications. The proposed design of the micropump involves a reusable configuration of the amplified piezoelectric actuator (APA) for micropump actuation and a disposable pump chamber. The pumping of the fluids occurs through the oscillation of the silicone rubber bossed diaphragm. The performance of a mechanical micropump depends on the oscillation amplitude of the diaphragm. Thus, the conventional approach of central excitation of the bossed diaphragm is replaced by a novel approach of annular excitation intended to enhance the deflection range, thus the volumetric performance of the micropump. An experimental comparative study is carried out to assess the deflection characteristics of central excitation and annular excitation of the bossed diaphragm. The maximum deflection measured with the annularly excited configuration of the bossed diaphragm is about 1953.4 ± 8.00 µm at 150 V, 43.5 Hz, which is superior to the maximum deflection of centrally excited configuration delivering 717.99 ± 4.00 µm at 150 V, 9.5 Hz. Further, the experimental studies aimed to fabricate and characterize the micropump with central and annular excitation approaches. The proposed micropump with central excitation delivered the maximum water flow rate of about 7.192 ± 0.147 ml min-1 and backpressure of 0.294 kPa at 150 V, 5 Hz. However, the enhancement of the deflection characteristics of the bossed diaphragm under annular excitation leads to performance enhancement of the micropump with the flow rate of 95.10 ± 0.444 ml min-1 and backpressure of 1.472 kPa at 150, 30 Hz. © 2021 IOP Publishing Ltd.
Analysis of annularly excited bossed diaphragm for performance enhancement of mechanical micropump
(Elsevier B.V., 2022) Mohith, M.; Karanth P, N.K.; Kulkarni, S.M.
Piezo actuated mechanical micropumps find extensive application in microfluidic devices for precise delivery of the fluids. The deflection of the diaphragm dramatically influences the performance of the mechanical micropump. The present work emphasises a novel method of annular excitation of the diaphragm to enhance the volumetric performance of the micropump. The proposed work incorporates a bossed diaphragm excited through a novel approach of annular excitation. The amplified piezoelectric actuator is used as a primary source of actuation. In the present work, theoretical and finite element methods are considered to analyse the deflection behaviour of the bossed diaphragm under central and annular excitation. Experimental characterisation is carried out to validate the results obtained from finite element analysis. The annular excitation of the bossed diaphragm delivers a higher range of deflection when compared with the conventional central excitation. The maximum simulated deflection of about 1998.4 µm is achieved with an annularly excited bossed diaphragm at 150 V, 45.5 Hz, which is far superior to the deflection range achieved with a conventional centrally excited bossed diaphragm with the deflection of 725.91 µm at 150 V, 9.96 Hz. The corresponding experimental deflection of annularly excited and centrally excited bossed diaphragm is about 1953.4 ± 8.00 µm at 50 V, 43.5 Hz and 717.99 ± 4.00 µm at 150 V, 9.5 Hz. © 2022 Elsevier B.V.

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