Qualification: 
Ph.D, M.Tech
sreenidhipr@am.amrita.edu

Dr. Sreenidhi P. R. received her B.Tech. degree in Electronics and Communication Engineering (2008), M.Tech. degree in VLSI and Embedded Systems (2014) and received her Ph.D. in Nanotechnology from National Institute of Technology, Calicut. She was working on Energy harvesting devices starting from nanomaterial synthesis to device fabrication and testing. She has published papers in reputed peer-reviewed journals like Nanoenergy Elsevier, Liquid crystal display Taylor and Francis, Applied nanoscience Springer, Material research express, IOP, High-performance Polymers, SAGE, Micro-nano letters, IET Applied Nanomaterials ACS, Applied Materials and Interfaces etc . She has received the best paper awards for the national conference (Electrical and Electronics Engineering Department) and the international conference (Chemical Engineering Department) held at the National Institute of Technology. Calicut. Her research interests include piezoelectric and contact electrification based devices for energy harvesting applications, Scanning probe microscopic techniques for nano-scale voltage characterization in nanomaterials. Currently, She is working as an Assistant Professor at the Department of Electronics and Communication Engineering, School of Engineering, Amrita Vishwa Vidyapeetham, Amritapuri, Kollam.

Publications

Publication Type: Conference Proceedings

Year of Publication Title

2020

Sreenidhi P. R., “Flexible PVDF-SrTiO3 Piezoelectric Nanogenerator for Energy Harvesting”, Centre for Nanotechnology Research (CNR), Vellore Institute of Technology. 2020.

2018

Sreenidhi P. R., “Triboelectric Nanoenergy Harvester Using Polymer As Active Layers(Best paper)”, National conference on recent trends in energy . Department of electrical engineering, NIT Calicut, Kerala, India, 2018.

2018

Sreenidhi P. R., “Contact Electrified Piezo-Tribo Nanoenergy Harvester (Best paper)”, First International Conference on Energy and Environment: Global Challenges. ICEE 2018 , Department of Chemical Engineering, NIT Calicut, Kerala, India, 2018.

2013

S. M. K. John and Sreenidhi P. R., “Low power glitch free dual output coarse digitally controlled delay lines”, 2013 International Conference on Advanced Computing and Communication Systems. IEEE, Coimbatore, India, 2013.[Abstract]


In deep-submicrometer cmos processes, time-domain resolution of a digital signal is becoming higher than voltage resolution of analog signals. This claim is nowadays pushing toward a new circuit design paradigm in which the traditional analog signal processing is expected to be progressively substituted by the processing of times in the digital domain. Within this novel paradigm, digitally controlled delay lines (DCDL) should play the role of digital-to-analog converters in traditional, analog-intensive, circuits. Digital delay locked loops are highly prevalent in integrated systems. The proposed paper addresses the glitches present in delay circuits along with area, power dissipation and signal integrity. The digitally controlled delay lines(DCDL) under study have been designed in a 90 nm CMOS technology 6 layer metal Copper Strained SiGe Low K Dielectric. Simulation and synthesis results show that the novel circuits exhibit no glitches for dual output coarse DCDL with less power dissipation and consumes less area compared to the glitch free NAND based DCDL. The most design intensive component of the DLL is the Digitally Controlled Delay Line (DCDL). A DCDL is a combinational circuit that delays its input by an open loop value that typically has a monotonic relationship with the digital setting input. Such delay value is not precisely defined and is subject to process, voltage, and temperature conditions. The average modern microprocessor contains multiple digital delay locked loops embedded in various subsystems. The vast majority of DCDLs in DLL applications are related to clocking and can also be used in absolute measurement of unknown delays (time to digital conversion).

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Publication Type: Journal Article

Year of Publication Title

2020

Sreenidhi P. R., “Nature-inspired PDMS cumulonimbus micro-energy-harvesting cloud”, Applied Nanoscience, Springer International Publishing, 2020.

2020

Sreenidhi P. R., John, S., Cherian, R., Subash, C. K., and Varghese, S., “Next-generation rooftop tribo–piezo electric energy harvesting from rain power”, Applied Nanoscience, vol. 10, no. 3, pp. 679-686, 2020.[Abstract]


In the present paper, authors report on the fabrication and testing of an energy harvester using polymer blends of PVDF and PDMS from raindrops. The films were characterised using microscopy techniques for morphology and frictional properties. The piezo–ferro–triboelectric nature of the blends was analysed using electrostatic force microscopy (EFM). The infrared (IR) spectroscopy was used for phase enhancements in neat as well as blends of the polymer. Three different configurations of the devices were fabricated and tested with polymer blend metal contact yielding an output of 16 V and 15.4 nA for a piezo–tribo area of 2.25 cm2. The charging characteristics of the device yielded a power density of 0.177 µW/cm2, and the device was also tested for knock sensing applications. A prototype of tribo–ferro energy harvester installed on a modelled house rooftop yielded an output voltage of 0.795 V for 10 ml of water dropped from 8 cm.

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2020

Sreenidhi P. R., Sivapriya, S., Karumuthil, S. Cherumanni, and Varghese, S., “Prototype of energy harvesting door handles using polymer nanocomposite”, Applied Nanoscience, vol. 10, no. 1, 2020.[Abstract]


Here in, we report on a prototype for energy harvesting from door handles for harnessing mechanical energy used during the opening and closure operation of doors. Three different morphologies of zinc oxide (ZnO) nanoforms namely ZnO nanorods (ZnO R), ZnO nanocrystallite (ZnO P) and ZnO nanoneedles (ZnO W) are blended at an optimum concentration of 10% with polydimethyl siloxane (PDMS) polymer. The frictional, triboelectric and converse piezoresponse of these films were studied using derived modes of atomic force microscopy. Three different structures of devices were fabricated by spin-coating, solution casting and tape casting techniques. Dispersion filler, graphite oxide (GO) nanosheets are added to the composite with superior electrical property. The device with solution casting was tested for various mechanical inputs, with and without external resistive loads connected. The device yielded an output voltage of 6.25 V on each approach-release operation. The device shows a power density of 0.73 µW/cm2 during an impact of 5 N. A laboratory prototype of door handle energy harvester was prepared on a comb electrode by tape casting the polymer nanocomposite recipe of PDMS + 10% ZnO W + 10% GO and generated a power density of 0.17 nW/cm2 by charging a 1F commercial capacitor.

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2020

S. Nair, Sreenidhi P. R., P. Kumar, and Nair, K., “Development of fully formulated eco-friendly nanolubricant from sesame oil”, Applied Nanoscience, vol. 10, no. 2, pp. 577-586, 2020.[Abstract]


In the present work, a biodegradable and non-toxic lubricant is formulated from sesame oil (SESO) with viscosity modifiers, antioxidants and antiwear additives. The significance of antiwear additives in SESO blended with antioxidants and viscosity modifiers is evaluated using analysis of variance (ANOVA). The formulated oil is tested for its biodegradability, toxicity, rheological, thermal, tribological and corrosive properties and is compared with commercially available SAE20W40 lubricant. The formulated lubricant is investigated to have better biodegradability, lower toxicity and good thermal properties than SAE20W40. Whereas its pour point, rheological properties, corrosive properties and tribological properties are comparable to that of SAE20W40.

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2019

S. C. K, Sreenidhi P. R., and Varghese, S., “Poly(vinylidene fluoride-trifluoroethylene)-ZnO Nanoparticle Composites on a Flexible Polydimethylsiloxane Substrate for Energy Harvesting”, ACS Applied Nano Materials, vol. 2, 2019.[Abstract]


In this article, we report on an energy-harvesting device using a hybrid flexible polymer nanocomposite as a tribo–piezo layer for energy generation. Piezoelectric nano zinc oxide (ZnO) and exfoliated graphene oxide (EGO) are used with a piezoelectric poly­(vinylidene fluoride-trifluoroethylene) (P­(VDF-TrFE)) polymer matrix to prepare the energy-generating layer. An enhancement of the β phase in P­(VDF-TrFE) is achieved by the method used for film preparation and the addition of ceramic nanoparticles to the matrix. The devices are tested under manual and mechanical tapping to generate electrical energy which is stored in a commercial capacitor. The fabricated hybrid polymer nanocomposite device generated 2.27 V (manual tapping), 11.6 V (qualitative analysis), and 28.3 V (quantitative analysis). Knock sensing action of the prototype device is also demonstrated. The hybrid polymer nanocomposite device with excellent touch sensitivity that is lightweight with distinguished energy-generating efficiency can be used in the self-powered energy-harvesting electronic devices of tomorrow.

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2019

S. C. K, Sreenidhi P. R., Valiyaneerilakkal, D. Uvais, Athiyanathil, S., and Varghese, S., “Electrospun Poly(Vinylidene Fluoride-Trifluoroethylene) based Polymer Nanocomposite Fibers for Piezoelectric Nanogenerators”, ACS Applied Materials & Interfaces, vol. 11, no. 43, pp. 40180-40188 , 2019.[Abstract]


The present work deals with the preparation, characterization and application of self-poled nanofibers using piezoelectric polymer poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), Zinc oxide (ZnO) and exfoliated graphene oxide (EGO) by electrospinning process. The characterization of nanofiber is carried by different techniques such as Field emission scanning electron microscopy (FESEM), Fourier transform Infra-red spectroscopy (FTIR), X-ray diffraction techniques (XRD) and Dynamic contact mode electrostatic force microscopy (DCEFM). The nanofiber based piezoelectric nanoenergy generator (PNEG) devices are fabricated for analyzing the energy generating efficiency. Piezoelectric hybrid nanofibers are exhibiting better energy generating efficiency and identified as potential material for energy harvesting applications.

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2019

Sreenidhi P. R., Nair, S., K, S. C., Valiyaneerilakkal, D. Uvais, Parameswaran, P., and Varghese, S., “α-and β-crystalline phases in polyvinylidene fluoride as tribo-piezo active layer for nanoenergy harvester”, High Performance Polymers, vol. 31, no. 7, pp. 785-799, 2019.[Abstract]


The manuscript introduces the use of non-electrically polled spin-coated thin polyvinylidene fluoride (PVDF) films as the active layers in a contact electrification-based nanoenergy harvester. The four-layered device utilizes both piezo and triboelectric effect coupled with electrostatic induction. The elucidation of potential generation during contact between crystalline phases (α and β) of PVDF layer material is investigated in the manuscript. Fourier transform infrared–attenuated total reflectance spectroscopy is carried out to illustrate the α- and β-phases in PVDF pellet, prepared film as well as the film after contact. Dynamic contact mode electrostatic force microscopy (DC-EFM) along with atomic force microscopy is used for the evaluation of reverse piezoelectric, local ferroelectric, triboelectric voltage and adhesive energy of the PVDF films before–after contact process. Quantum chemical calculation is performed using density functional theory to explain possible electron transitions in the active layers between the cylindrically symmetric α-phase and electrical double layer charges in the β-phase of PVDF. The interface study of the film is also carried out both experimentally using DC-EFM and through quantum chemical calculations. The fabricated device with the hybrid piezo-tribo layer promises to be a simple and low-cost energy source for the next-generation self-powered electronic devices. The device can also be used as knock sensor in engines as well as a capacitor.

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2018

Sreenidhi P. R., K, S. C., Lokasani, B., and Varghese, S., “Flexible nanoenergy harvester using piezo-tribo functional polymer and carbon fibre as electrodes”, Materials Research Express, vol. 5, no. 7, 2018.[Abstract]


Micro-energy harvesting has gained immense interest among the research community due to the requirement for self-powering of sensor units in unapproachable environments. Use of simple, low cost, flexible energy harvester aids generation of energy from ambient environments. The present work proposes two devices under test(DUT) with different electrodes namely copper(DUT1) and carbon fibre (DUT2), polymers Polyvinylidene fluoride (PVDF), Polydimethylsiloxane (PDMS) as a functional charge generating materials. The piezoelectric and triboelectric characterisation of polymer films is performed using Dynamic contact mode electrostatic force microscopy(DC-EFM). The proposed DUT1 and DUT2 generates an 8 Vpp and 9 Vpp during human finger tapping. The qualitative and quantitative analysis of DUT1 and DUT2 generated an output voltage of (8.5 V, 12.35 V) (high pressure),(13.5 V, 14.1 V) (285 rpm) respectively. The carbon fibre electrode based flexible device generated an output voltage of 9 V, 10 V and 2.275 V when subjected to biomechanical operations such as finger assisted tapping, press and release as well as bending operations. The device with copper electrode generated 0.32 nJ of energy and power density per unit area of 2.37 pW cm⁻² in a single tap cycle. The DUT2 generated thrice the energy and power density than that of DUT1. The DUT2 thus promises to be an efficient, low-cost, flexible energy harvester with PVDF as well as PDMS polymers as a functional layer.

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2018

N. John, Sreenidhi P. R., and Varghese, S., “Ferroelectric polymer nanocomposite alignment layer in twisted nematic liquid crystal devices for reducing switching voltage”, Liquid Crystals, vol. 46, no. 5, pp. 736-742, 2018.[Abstract]


Twisted nematic liquid crystal device (TNLCD) was fabricated using a ferroelectric zinc oxide (ZnO)-doped polyimide alignment layer. The ferroelectric nanoparticle can produce a local electric field, which can trigger the orientation of liquid crystal molecule and reduces the switching voltage. The uniform dispersion of ferroelectric ZnO nanoparticles in the alignment layer was studied using field emission scanning electron microscopy and atomic force microscopy. The ferroelectric property of ZnO-doped polyimide was investigated using dynamic contact electrostatic force microscopy. An increased local electric field due to the presence of nano ZnO was confirmed with the help of scanning tunnelling microscopy. An augmentation of capacitance was observed with an increase in concentration, which substantiates the reduction of switching voltage of TNLCD with the modification of ferroelectric nanoparticle-doped alignment layer.

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2017

S. C. K, Sreenidhi P. R., and Varghese, S., “Piezo-tribo nanoenergy harvester using hybrid polydimethyl siloxane based nanocomposite”, Nano Energy, vol. 40, pp. 487-494, 2017.[Abstract]


The authors propose a hybrid nanocomposite based piezo-tribo nanoenergy harvester using polydimethylsiloxane (PDMS) which is of low cost, fabricated in simple steps, without external poling of the film and is mass producible. A nanocomposite of ZnO nanorods, exfoliated graphene oxide and multiwalled carbon nanotubes are dispersed in PDMS resin. Dynamic contact mode electrostatic force microscopy is performed to analyse the ferroelectric and piezoelectric property of the prepared hybrid nanocomposite. Using the above nanocomposite, a device is fabricated which works on combined effect of piezoelectric and triboelectric characteristic of materials under study. Qualitative studies are performed on this using force sensitive resistor. The device generated a maximum voltage of 7.5 V in the case of higher pressure (analog reading > 800). Quantitative studies are conducted using a universal vibration apparatus at various revolutions per minute and maximum of 15.25 V is obtained. Hybrid nanocomposite device is scaled up in dimension and is tested under irregular finger assisted tapping, press-release operation and human footsteps yielding an output voltage of 36 V, 40 V and 50 V respectively. The obtained alternating voltages are rectified and stored into a commercial capacitor. Enhancing the current characteristics of the piezo-tribo device will prove to be an excellent substitute for energy harvesting and self-powering applications.

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2017

Sreenidhi P. R., S. Karumuthil, C., Valiyaneerilakkal, U., and Varghese, S., “Nanoscale static voltage generation and its surface potential decay using scanning probe microscopy”, Micro Nano Letters, vol. 12, pp. 928-933, 2017.[Abstract]


This work aims at the manipulation of nanoscopic voltage produced through uniform and non-uniform rubbing in neat unpolarised polymer polyvinylidene fluoride. A metal-insulator configuration is considered for the analysis. The decay of surface potential in such a configuration is also addressed in this work. The polarity of the voltage observed on the film depends on the work function of the metal electrode in contact as well as the electronegativity of polymeric material under study. Scanning probe microscopic techniques such as dynamic contact mode electrostatic force microscopy, scanning tunnelling microscopy are used for the investigation of specific electrostatic potential variation on polymer films. Effect of contact electrification leads to nanoscopic domains of voltage generation on the surface of the tribolayers. Electrostatic potential developed on the surface of unrubbed polymer film using modulated tip is in the range of 20-40 mV. The range of voltage generated increased from 20 to 125 mV in the case of rubbed polymer films. Charge retention is discussed through obtaining surface potential decay trend at various intervals. This also plays an important role in the generation of the voltage as well as the current. The above scenario has been demonstrated in both rubbed and unrubbed scenarios. Charge decay is observed to be gradually decreasing from 40 to 29.5 mV in unrubbed surface and 125 to 14 mV in rubbed surface for various time intervals. The obtained results suggest insignificance of triboelectric series on contact electrification between similar tribolayers.

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Reviewer

Journals

  • ACS Applied Materials and Interfaces
  • Elsevier Nanoenergy SAGE
  • Journal of Thermoplastic Composite Materials