Coupled effects of an electroplated gold layer and damper holes drilled by Electro Chemical Discharge Machining (ECDM) process on the performance improvement of a quad beam capacitive accelerometer is presented in this paper. A simple quad beam-proof mass configuration with its beams located symmetrically at the centre of all the edges of the proof mass and connected to an outer supporting frame is considered in the present study. For a fixed damping ratio, prime-axis sensitivity of the sensor is increased by the damper holes whereas an electroplated gold layer improves the prime-axis sensitivity, cross-axis sensitivity, and Brownian Noise Equivalent Acceleration (BNEA). Moreover, the increased weight of the proof mass due to an electroplated gold layer further reduces the damping of the device which in turn helps to increase the prime-axis sensitivity more. A new figure of merit called Performance Factor (PF), defined as the ratio of the product of the prime-axis sensitivity and resonant frequency to the cross-axis sensitivity at a fixed damping ratio of 0.7 is used as a quantitative index to evaluate the performance improvement caused by the coupled effects of gold electroplating and ECDM processes. Simulation results show that for a device with damper holes of 8 μm diameter and electroplated gold layer of dimensions 3,000 μm × 3,000 μm × 20 μm, the prime-axis sensitivity is increased by more than 500 times, rotational cross-axis sensitivity and BNEA are reduced by around 10 and 30%, respectively and the PF is improved by around 482 times at a fixed damping ratio of 0.7. © 2011 Springer-Verlag.

Ravi Sankar A

Electronics

School of Electronics Engineering

Chennai Campus

Bindu V.S.S

Das S.

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Microsystem Technologies

In the present work, we realize a miniaturized piezoresistive accelerometer with high magnitude of prime-axis signal and a very low cross-axis signal. Numerical simulations are performed to investigate the electro-mechanical response of three structures with different flexure positions and an electroplated gold layer. Of the three structural configurations, one structure with the proof mass-edge-aligned-beams and an electroplated gold film has better performance with lesser real estate consumption. Experimental results show that a fabricated sensor depicts around 20% improvement in the prime-axis signal and a maximum reduction of 7.6% in the cross-axis signal compared to other structures. © 2019, © 2019 IETE.

IETE Journal of Research

Influence of the Flexure Position and a Thick Gold Film on the Performance of Beam-Mass Structures

Microfluidics is an emerging field giving rise to a number of scientific developments with wide applications in proteomics, genomics, DNA analysis, drug delivery systems and lab-on-a-chip. Among the various microfluidic structures, microchannels form an integral part of Lab-on-a-chip devices for clinical diagnosis. The geometrical accuracy and surface finish quality of the microchannels affect the performance of microfluidic systems, thereby demanding a precise microfabrication technique for realizing microchannels. Spark assisted chemical engraving (SACE) is an effective hybrid micromachining technique used for micro-structuring non-conducting substrates such as glass and ceramics. In the present work, we report on a room temperature coated thick insulating film for improving the quality of the microchannels realized using a SACE process. The insulator film coated around a tool electrode confines the spark discharges only to the bottom surface of the tool. Moreover, the proposed insulator coating methodology does not require any cost intensive equipment, carrier gases, vacuum units and a clean room environment. Experimental results demonstrate that for same process parameters a micro-channel fabricated using an insulated tool has its overcut reduced by 57.8% and machining depth improved by 19.53% with a smooth surface and regular edges as compared to the channels realized using an uninsulated tool. © 2017 Taylor &amp; Francis.

Materials and Manufacturing Processes

Fabrication of precise microchannels using a side-insulated tool in a spark assisted chemical engraving process

In the present study, a detailed experimental investigation is carried out on a constant velocity-feed drilling technique of an electrochemical discharge machining (ECDM) process to fabricate micro-holes on quartz substrates. First, cylindrical micro-tools of four different diameters (145 μm, 195 μm, 300 μm and 400 μm) with varying tool feed rates (TFRs) (0.3 μm s-1-1.9 μm s-1) are considered to study their influence on the precision of fabricated micro-holes while using a 30 wt% NaOH solution as an electrolyte, a machining voltage of 30 V and an initial working gap of 5 μm. Minimum micro-hole diameter and overcut were achieved at a TFR 0.8 μm s-1 for the cylindrical tools of all diameters. Considering 0.8 μm s-1 as an optimal TFR, the influence of tool shape on the quality metrics was investigated using a spherical shaped tool electrode having a ball diameter of 145 μm and a spindle diameter of 90 μm. A micro-hole realized using the spherical shaped tool shows that the entrance diameter, entrance overcut, central diameter and central overcut are reduced by 12%, 29%, 28% and 67% respectively as compared to that realized using a cylindrical tool for the same process parameters. Micro-holes with improved precision and aspect ratio are achieved without using cost intensive equipments, feedback mechanisms, coated tools and tool rotation. © 2018 IOP Publishing Ltd.

Journal of Micromechanics and Microengineering

Fabrication of precise micro-holes on quartz substrates with improved aspect ratio using a constant velocity-feed drilling technique of an ECDM process

Piezoresistive acceleration sensors have found a wide range of applications for the last four decades. However, in recent times, high performance piezoresistive acceleration sensors with lower footprint are in demand, especially in the fields of consumer electronics and biomedical engineering. The design of such sensors remains a challenging task due to the competing requirements of high electrical sensitivity (∆R/R) and resonant frequency (f0) along with low device footprint. In this paper, we elaborate the design and optimization of a highly miniaturized doubly clamped acceleration sensor with an integrated silicon nanowire as a piezoresistor. The diminutive size of the silicon nanowire helps in reducing the device foot print. The design is performed using two methods: (1) electrical approach and (2) mechanical approach. In the electrical approach, the conventional bulk silicon diffused piezoresistors are replaced with a silicon nanowire without changing the dimensions of the original structure. It is shown that compared to the conventional design, a silicon nanowire based sensor exhibits 2.51 times better performance in terms of electrical sensitivity. One of the major constraints with miniaturized high performance acceleration sensors is reduced resonant frequency. Therefore, in the mechanical approach we have devised a geometrical optimization technique to miniaturize the sensor geometry by keeping its resonant frequency constant. Numerical simulations are performed to validate the proposed miniaturized sensor with an integrated silicon nanowire as the piezoresistor. The sensor performance is evaluated with a new performance factor given as (ΔR/R)f02/Diesize, which takes into account the electrical sensitivity, the resonant frequency and the die size of the sensor. Results show that the proposed sensor design with an integrated silicon nanowire has 48.2 times better performance factor than a bulk piezoresistor based conventional acceleration sensor. © 2016, Springer-Verlag Berlin Heidelberg.

Design and optimization of a doubly clamped piezoresistive acceleration sensor with an integrated silicon nanowire piezoresistor

Electrochemical discharge machining (ECDM) process is a recent non-traditional machining technique used for structuring insulating materials like glass and ceramic substrates. In this work, systematic experimental investigations have been carried out to study the electrical and 2-D machining characteristics of an ECDM process. The influence of various process parameters like electrolyte type, electrolytic concentration, tool travel rate (TTR) and applied voltage on the process characteristics have been studied. Two different electrolytes, i.e., KOH and NaOH with concentrations varying from 10 to 50 % have been used to study their effect on critical voltage (Vc) and critical current (Ic). A cylindrical tungsten carbide tool of diameter 0.4 mm with varying TTRs (ranging from 0.3 to 4 mm/min) and an applied voltage varying from Vc + 2 V to Vc + 5 V is used for realizing microchannels. The influence of these parameters on the quality factors such as geometric accuracy, surface smoothness and channel outlines are explored using the optical images of the machined channels. Experimental results demonstrate that precise channels with smooth surface, and regular channel edges can be obtained at an applied voltage of Vc + 4 V and TTRs between 1 and 2 mm/min. © 2016, Springer-Verlag Berlin Heidelberg.

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ISSN	0946-7076
Open Access	0