Hafzaliza Erny Zainal Abidin

Design of interdigital structured supercapacitor for powering biomedical devices

Energy scavenging has become an increasingly popular option for powering electronic devices as a long lasting power sources. A MEMS piezoelectric based energy scavenging system consists of a MEMS piezoelectric generator, a voltage multiplication circuit and an energy storage unit. Supercapacitor has the potential to be an excellent power storage material for renewable energy sources. The interdigital structured supercapacitor consists of silicon as the substrate, nickel as current collectors and polyvinyl alcohol based gel as a solid state electrolyte. Coventorware ver. 2008 was used in this work to simulate the working structure of supercapacitor. Physical parameters such as length of fingers, electrode spacings, and electrode widths strongly influence the capacitance value of the interdigital structured supercapacitor. From the simulation, the maximum charge density value is 4.1×10−6 pC/ μm2 and the maximum capacitance achieved is 0.116pF for finger length of 2500 μm. The results presented here is crucial in obtaining an optimal design for interdigital structured supercapacitor to be used for powering biomedical devices.

Electrical performances based on two different structured of micro supercapacitor electrodes

This paper discusses electrical performances of the micro supercapacitor such as cyclic voltammetry and charge discharge between two different structure of electrodes. The microsupercapacitor was constructed of Polypyrrole (Ppy) coated nickel electrode as current collector and polyvinyl alcohol (PVA) as solid state electrolyte. The electrochemical performances of the microsupercapacitor such as cyclic voltammetry also typically known as I-V curve and a typical time based charge discharge curve were investigated with different structured of electrode which is interdigital electrode and planar electrode for the same layout. In Comsol Multiphysics ver. 4.2a, the Secondary Current Distribution and Transport of Diluted Species has been selected as the Application module. I-V curve for the micro supercapacitor with the two structured of electrodes was simulated. The transport of a reduced and an oxidized species is described by time-dependent mass transfer principles for diffusion under dilute conditions. The maximum current response for the interdigital electrode is 5.5 A/m and for the planar electrode is 0.025 A/m. For the interdigital electrode, the maximum voltan achieved at 0.5 V same for the planar electrode with different time. Discharging process for interdigital and planar electrode occurred when the value of voltage decreasing and back to zero at 1s and 10 s respectively.

Characterization of planar interdigital micro supercapacitor with PECVD graphene as electrodes at low temperature

Graphene has recently gained much interest in applications such as energy storage, catalysis and gas sensing. In terms of energy storage, micro supercapacitor has attracted a lot of interest in fields such as bioMEMS, biomedical implants such as cardiac pacemaker and the promising field of powering small electronic devices. In this paper, the structure of the micro supercapacitor PECVD graphene on electrodes consists of SiO2 substrate, graphene on Nickel (Ni) electrodes, with Polypyrrole (Ppy), graphene and Polyvinyl Alcohol (PVA) layers. To improve performance, graphene is one of the more promising material being investigated for micro supercapacitor electrodes due to several advantages such as high specific surface area and high electron mobility. Graphene was then grown on the Ni electrodes using the Plasma- Enhanced Chemical Vapor Deposition (PECVD) process. The graphene growth structure on the interdigital electrodes of micro supercapacitor was characterized by Raman Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-Ray (EDX) and Atomic Force Microscopy (AFM). A Raman spectrum of graphene growth on interdigital electrode has identified three peaks which are the D band, G band and 2D band. The broad peaks at 1340 cm-1 and 1580 cm-1 correspond to the D and G bands, respectively.

Growth time dependent of high quality graphene on interdigital electrodes for MEMS supercapacitor

This paper discusses direct growth of graphene on the interdigital electrodes for MEMS supercapacitor application. In addition, a high quality graphene was grown by using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) at temperature of 1000°C at various deposition time from 2–10 minutes at fixed power of 40 Watt. The graphene growth structure on the interdigital electrodes was characterized by Raman spectroscopy and atomic force microscopy (AFM). Raman spectra indicate that the intensity ratio of the 2D band and G band (I2d/Ig) is 1.00 and the value of FWHM is 54.26 cm−1 which produced a good quality bilayer graphene. Atomic Force Microscopy (AFM) result shows the surface roughness of the structure is 68.56nm.

PECVD growth of high quality graphene on interdigital electrodes of MEMS supercapacitor

In the field of science, there is a significant interest in graphene due to its extraordinary properties such as high electrical conductivity, good electrochemical stability and excellent mechanical behavior. This paper presents the direct graphene growth on interdigital electrodes by plasma enhanced chemical vapor deposition (PECVD) using Ni catalyst and methane (CH4) as the carbon source. The 100 nm of Ni was deposited on the top of SiO2 substrate functional as catalyst and electrode of MEMS supercapacitor. The growth of graphene was investigated at temperature 1000°C at 10 minutes and at fix power of 40 Watt. The morphology and structure of as- grown graphene were characterized by Raman spectroscopy, Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM). From Raman spectra, it is observed that the intensity ratio of the 2D band to G band produced a good quality bilayer graphene.

Structural analysis of graphene growth on interdigital electrodes micro supercapacitor by PECVD at various temperatures

Planar interdigital micro supercapacitor with the graphene growth via Plasma Enhanced Chemical Vapor Deposition (PECVD) with the different temperatures has been investigated in this works. The structure of the micro supercapacitor consists of SiO2 substrate, graphene growth on Nickel (Ni) electrodes coated with Polypyrrole (Ppy) and Polyvinyl Alcohol (PVA) layers as solid state electrolyte. A single layer of graphene which has sp2 hybridized carbon atoms is one of the promising material that has been used for micro supercapacitor electrodes due to several advantages such as high specific surface area, high thermal conductivity and high electron mobility. PECVD method is a main method for graphene growth due to the advantages such as high growth selectivity and good control in nanostructure patterning. In this works, the graphene growth on the interdigital electrodes was investigated in various temperatures from 400°C to 1000°C. The graphene growth structure on the interdigital electrodes of micro supercapacitor was characterized by Raman Spectroscopy. Raman Spectroscopy was carried out using a 532 nm laser excitation. A Raman spectrum of graphene was observed on interdigital electrode have identified three peaks which is D band, G band and 2D band. Raman spectra show that the intensity ratio of the 2D band and G band at 1000°C of 0.43 indicating a good quality of multilayer graphene growth.

Interdigitated MEMS Supercapacitor for Powering Heart Pacemaker

Power MEMS can be defined as microelectromechanical systems for power generation and energy conversion. Energy harvesting has become an increasingly popular option for powering electronic devices as a long-lasting power source. Energy scavenging is defined as the process by which the energy is derived such as vibration, solar, wind, and thermal. Energy harvesting from the environment can prolong the life cycle and reduce the maintenance costs of electronic devices. Among the various sources of energy storage, Among the various of energy storage, supercapacitor has recently gained much interest in fields such as bioMEMS, biomedical implants and power electronic devices due to its advantages such as high power density, rapid charge and discharge and unlimited number of recharge cycles. In biomedical and bioMEMS systems, an energy storage device is needed to power other active biomedical devices within the system. For implantable devices such as a heart pacemaker, the power requirement is in the range of 30–100 μW. Microsupercapacitors play an important role in energy harvesting system, such as collecting energy from ambient energy sources. Human body is very resourceful in generating micropower in the form of heat dissipation, deformation of elastic tissue, and motion. Due to the advantages of MEMS energy harvesting system, the system can be use widely for biomedical implant devices, such as heart pacemakers and hearing aids, and can be used for a long time and without the need for battery replacement. In this work, planar and double-stacked interdigital electrode supercapacitor designs were modeled using Coventorware software. From simulation, it is observed that for planar structure, the specific capacitance is 0.22 mF/cm−2, and for double-stacked structure specific capacitance can be increased to 0.48 mF/cm−2. In terms of specific power, the planar structure produces 0.99 mW/cm−2, and the double-stacked structure produces 2.18 mW/cm−2. These results highlight the superiority of the doublestacked MEMS interdigital supercapacitor design compared with its planar counterpart

3C-SiC-on-Si based MEMS packaged capacitive pressure sensor operating up to 500 ºC and 5 MPa

This paper reports a packaged MEMS capacitive pressure sensor based 3C-SiC using bulk-micromachining technology that operates on the pressure up to 5.0 MPa and temperature up to 500 oC. The diaphragm employs a single-crystal 3C-SiC thin film that is back-etched from its Si substrate. A photosensitive ProTEK PSB is used as a protection mask layer to reduce the process steps. We compare our results with similar work that also employs a single-crystal 3C-SiC-on-Si capacitive pressure sensor with ceramic package. The MEMS capacitive pressure sensor is employed with 3C-SiC that was performed using hot wall low pressure chemical vapor deposition (LPCVD) reactors at the Queensland Micro and Nanotechnology Center (QMNC), Griffith University. This paper also focuses on comparing those two highest efficiency distributions in MEMS capacitive pressure sensor device to other types of MEMS capacitive pressure sensor. Different temperature, hysteresis and repeatability tests are presented to demonstrate the functionality of the packaged MEMS capacitive pressure sensor. As expected, the output hysteresis has low hysteresis (less than 0.05%) which has inflexibility greater than traditional silicon. By utilizing this low hysteresis was revealed the packaged MEMS capacitive pressure sensor has high repeatability and stability of the sensor.