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2023 | Buch

# Microactuators, Microsensors and Micromechanisms

## MAMM 2022

herausgegeben von: Ashok Kumar Pandey, Prem Pal,  Nagahanumaiah, Lena Zentner

Buchreihe : Mechanisms and Machine Science

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### Über dieses Buch

This book brings together investigations which combine theoretical and experimental results related to such systems as flexure hinges and compliant mechanisms for precision applications, the non-linear analytical modeling of compliant mechanisms, mechanical systems using compliance as a bipedal robot and reconfigurable tensegrity systems and micro-electro-mechanical systems (MEMS) as energy efficient micro-robots, microscale force compensation, magnetoelectric micro-sensors, acoustical actuators and the wafer bonding as a key technology for the MEMS fabrication.

The volume gathers the contributions presented at the 6th Conference on Microactuators, Microsensors and Micromechanisms (MAMM), held in Hyderabad, India in December 2022. The aim of the conference was to provide a special opportunity for a know-how exchange and collaboration in various disciplines concerning systems pertaining to micro-technology.

The conference was organized under the patronage of IFToMM (International Federation for the Promotion of Mechanism and Machine Science).

### Inhaltsverzeichnis

##### Free Vibration of Compliant Mechanisms Based on Euler-Bernoulli-Beams

This paper presents an analytical approach for computing the natural frequencies of planar compliant mechanisms consisting of any number of beam segments. The approach is based on the Euler-Bernoulli Beam theory and the transfer matrix method (TMM), which means there is no need for a global dynamics equation, but instead low-order matrices are used which result in high computational efficiency. Each beam segment is elastic, thin, has a different rectangular cross-section or a different orientation and is treated as an Euler-Bernoulli beam. The approach in principle does not differentiate between the flexure hinges, and the more rigid beam sections, both are treated as beams. The difference in stiffness solely results from the changes in the cross sections and length. A finite element analysis (FEA), as often used in practical applications, has been carried out for various geometries to serve as state-of-the-art reference models to which the results obtained by the presented analytical method could be compared. Various test specimens (TS) consisting of concentrated and distributed compliance in various degrees of complexity were produced and measured in free- and forced vibration testing. The results from experiments and the FEA compared to those of the proposed method are in very good correlation with an average deviation of 1.42%. Furthermore, the analytical method is implemented into a readily accessible computer-based calculation tool which allows to calculate the natural frequencies efficiently and to easily vary different parameters.

Vivien Platl, Leo Lechner, Thomas Mattheis, Lena Zentner
##### Towards Topology Optimization of Pressure-Driven Soft Robots

Soft robots are made of compliant materials that perform their tasks by deriving motion from elastic deformations. They are used in various applications, e.g., for handling fragile objects, navigating sensitive/complex environments, etc., and are typically actuated by Pneumatic/hydraulic loads. Though demands for soft robots are continuously increasing in various engineering sectors, due to the lack of systematic approaches, they are primarily designed manually. This paper presents a systematic density-based topology optimization approach to designing soft robots while considering the design-dependent behavior of the actuating loads. We use the Darcy law with the conceptualized drainage term to model the design-dependent nature of the applied pressure loads. The standard finite element is employed to evaluate the consistent nodal loads from the obtained pressure field. The robust topology optimization formulation is used with the multi-criteria objective. The success of the presented approach is demonstrated by designing a member/soft robot of the pneumatic networks (PneuNets). The optimized member is combined in several series to get different PneuNets. Their CAD models are generated, and they are studied with high-pressure loads in a commercial software. Depending upon the number of members in the PneuNets, different output motions are noted.

Prabhat Kumar
##### Compliant Finger Gripper Based on Topology Optimization

We present the design of a compliant finger based on the topology optimization method through Hill Climber stochastic search. The compliant finger is composed of an arrangement of beams, whose behavior is studied under the formulation of large deformation co-rotational beam elements. The design optimization seeks to maximize deflection of the tip of the compliant finger with the lowest possible input torque and the mechanical advantage via the contact force between the compliant finger and a free-form shaped object. Large tip deformation is sought along a desired path. The actual path traced by the candidate mechanism and the desired path are compared through their Fourier descriptors. Computation of the contact force is performed between the surfaces of Euler-Bernoulli beam and a prescribed free-form shape.

Estefania Hermoza Llanos, Mathias Hüsing, Burkhard Corves, Anupam Saxena
##### Development of a Database to Simulate and Adapt Compliant Mechanisms to a Given Characteristic for Improving Energy Efficiency of a Walking Robot

Compliant mechanisms with variable geometric parameters are investigated for the application in a bipedal robot to improve its walking efficiency. These mechanisms have nonlinear torque-angle characteristics and act like torsion springs to change the systems free oscillation frequency. High energy efficiency is achieved if the free oscillation frequency matches the step frequency, meaning the that the robot walks in resonance. For this purpose, the desired characteristic of the optimized elastic coupling is identified via optimization. Then, a database is developed, which consists of boundary conditions and beam elements. In this paper, there are three boundary conditions and three beam elements for demonstration purpose. To simulate a large number of compliant mechanisms with different characteristics, two boundary conditions and a beam element can be combined. The boundary conditions serve as bearing types to connect the beam element to the thighs of a robot. The large deformation behavior is assumed to be simulated by the Euler-Bernoulli beam theory, which is validated by FEM models. Thus, the desired characteristic from the proceeding optimization process is realized by a specific compliant mechanism.

Marten Zirkel, Yinnan Luo, Ulrich J. Römer, Alexander Fidlin, Lena Zentner
##### Analytical Characterization of Spatial Compliant Mechanisms Using Beam Theory

Due to the advantages of compliant mechanisms, they are widely used in technical fields such as precision engineering, measurement and medical technology. The movement of the mostly monolithically designed mechanisms is primarily achieved by bending the individual structural sections. Due to geometric nonlinearities caused by large deflections, the analytical description of the deformation behavior under the influence of external loads is not trivial. While plane compliant mechanisms can be reliably calculated with different models, the analysis of spatial compliant mechanisms is accordingly more difficult. Due to the complexity of the motion, simplifications are often made in the model assumptions, which have a detrimental effect on the precision of the results. Therefore, this paper presents a method to apply nonlinear beam theory to complex spatial structures that can include both curved sections and sections with non-constant cross-sections. Using selected examples of varying complexity, the model is validated using FEM simulations. In addition, a procedure to characterize branched spatial compliant mechanisms with the proposed analytical model and to calculate their deformation is explained. By efficiently solving the analytical model numerically, the deformed state of the mechanism can be obtained in seconds. Therefore, the model is particularly suitable for early stages of development or iterative synthesis tasks.

Stefan Henning, Lena Zentner
##### Study of Curved Beam Based Displacement Amplifying Compliant Mechanism for Accelerometer Design

The performance of an inertial micro-device largely depends on its displacement sensitivity. Different techniques like mechanical amplification using compliant mechanisms, geometric anti-spring design, and mode-localized can be employed for improving it. In this paper, a compliant mechanism-based accelerometer is studied and the design is optimized by incorporating a curved shaped beam. A detailed analysis presents interesting insight about the operation of the curved-shaped displacement amplifying compliant mechanism (DaCM). Study suggest that a larger sense mass displacement could also be achieved by DaCM with smaller geometrical amplification. The design simulations are carried out in finite element analysis (FEA) based CoventorWare and COMSOL Multiphysics simulator.

Mithlesh Kumar, P. Krishna Menon, Ashok Kumar Pandey
##### Model of a Micromechanical Modal-Localized Accelerometer with an Initially Curvedmicrobeam as a Sensitive Element

The present study is devoted to mathematical modeling of the proposed new architecture of a microelectromechanical mode-localized acceleration sensor (MEMS accelerometer/gravimeter) with a sensitive element in the form of a clamped-clamped microbeam with an initial curvature, made in the form of the first asymmetric mode of free oscillations. The paper shows that with an asymmetric form of the initial curvature in the region of positive axial forces, there are zones of proximity of the frequency branches corresponding to the second symmetric and the first asymmetric oscillation modes. The proposed configuration of the oscillation excitation and output signal pickup electrodes makes it possible, with the help of a feedback loop, to stabilize the oscillation amplitude at the required level according to the working (third) symmetric form and, at the same time, measure the oscillation amplitude associated with the change in the value of the measured component of the external acceleration according to the asymmetric form. The effect of energy exchange between the symmetric and asymmetric modes of the sensitive element can be used as the basis for the development of a new subclass of high-precision resonant sensors with amplitude pickup of the output signal. The parametric studies of the nonlinear statics and dynamics of free oscillations of the sensing element have shown a high level of potentially achievable accuracy of measurements of the external acceleration.

Nadezhda Mozhgova, Alexey Lukin, Ivan Popov
##### Different Beam Configurations for Compliant Mechanism-Based MEMS Accelerometer

In this article, a compliance-based displacement amplifier has been analyzed. The utility of a couple of variations within a pre-existing compliant mechanism has been systematically investigated. The presented modifications within the pre-existing design can help to get a large output displacement. The suggested modification within the design doesn’t improve the amplification ratio, but it can cause a large increase in the output displacement of the amplifier for the given input force. Such characteristics of an amplifier are very helpful in a device like an accelerometer in which proof mass provides a certain inertial force. Here, the modified displacement amplifier has been considered to be included in a capacitive sensing-based MEMS accelerometer. The influence of beam configurations on the performance of MEMS accelerometer is analyzed, and the dimensions are chosen to get the optimum performance. It is found that the proposed variations in the design are helpful to get larger sensitivity. They are extremely useful to be included within the design when the allowed minimum size of the beams is larger due to fabrication limitations. Natural frequencies of the MEMS accelerometer have been calculated numerically and analytically where a good agreement has been found. The presented study assures improvement in the device performance through suggested modifications within the compliant mechanism.

Nikul Jani, Mithlesh Kumar, P. Krishna Menon, Ashok Kumar Pandey
##### Design and Analysis of the Two-Level Accelerometer

The accelerometer is the sensor that detects the change of acceleration, has many applications in transportation, industry, navigation, and medical devices. This paper introduces a new design of the micro accelerometer that detects two distinct acceleration values. The design model is a micro-electro-mechanical system (MEMS). The device is a monolithic structure comprising two compliant bistable mechanisms that connect series to generate two-level distinct positions in the motion. The accelerometer operates based on the capacitive spring-mass system. The comb drives assist in indicating the acceleration value with the sensing capacitor utilized to archive the electrical output signal. The accelerometer works only in a direction; therefore, the reset mechanism is introduced to install the initial stage of the device. The electrothermal V-beam is employed to move the mechanism from the first or second level position to the initial position. The testing mechanism is also presented, which has the function of examining the operation of the device. The nonlinear behavior of the mechanism is investigated and analyzed by finite element method. The device can detect the two accelerations, 13g and 48g. The simulation of the mechanism assists in evaluating the operation of the mechanism. The accelerometer has great potential for energy-saving applications.

Hoang Bao Thien Nguyen, Thanh Lam Tran, Ngoc Dang Khoa Tran
##### Microchannel Induced Tailoring of Bandwidth of Push-Pull Capacitive MEMS Accelerometer

High quality capacitive accelerometers with appreciable operation bandwidth are being employed in different high-end defence applications. This paper discusses a novel concept of introducing microchannels in the push-pull capacitive accelerometer structure to control the damping arising due to squeeze film effect. The width and depth of the microchannels are varied to study the damping in the accelerometer structure. The damping factor of accelerometer structure is reduced from 50.2 to 2.51 and its corresponding 3 dB bandwidth is improved from 62.24 to 1.26 kHz due to the introduction of the microchannels.

Nidhi Gupta, Siva Rama Krishna Vanjari, Shankar Dutta
##### A Comparison of Ring and Disk Resonator Gyroscopes Based on Their Degenerate Eigenmode Shapes

Micromachined gyroscopes are beginning to compete with their macro-scale counterparts in terms of performance. This has been made possible because of a remarkable design change that has come to be known as a Disk Resonator Gyroscope (DRG). The design of a DRG can be thought of as an extension of the Ring Resonator Gyroscope (RRG) or vibratory ring gyroscope (VRG). After experimenting with various ring configurations and their suspensions attached to the ring, research has now moved to multiple configurations of DRGs. Central to all these designs are the degenerate eigenmode shapes: a pair of mode shapes for the same frequency. As one mode shape is used for resonant electrostatic actuation and another for sensing the energy transferred to it due to Coriolis acceleration, mode shapes decide the change in capacitance per unit angular rate. The objective of maximizing the capacitance change is to be balanced with the performance constraints on keeping the eigenfrequency low (but not too low) and quality factor high. In this paper, we compare different designs of ring and disk resonators from the literature in terms of eigenfrequency and mode shapes. We conclude that it is beneficial to have the mode shape of a gyroscope design close to the elliptical mode shape of a free ring.

Kandula Eswara Sai Kumar, Karthik Raveendranath, Sudhanshu Sekhar, G. K. Ananthasuresh
##### Parametric Tuning of Natural Frequencies of Tuning Fork Gyroscope

The sequence of mode shapes play a vital role in designing a dual mass tuning fork gyroscope (TFG). To avoid loss of energy, a desired separation of frequencies between operating modes (out-of-phase drive and sense) and parasitic modes is required. Hence, regulation of mode shapes is an essential criterion in TFG design. In the present work, the influence of several crucial parameters such as coupling mechanisms and dimensions of folded beams on the in-plane frequencies are studied numerically by using finite element based COMSOL software.

Rakesha Chandra Dash, Rakesh Tirupathi, P. Krishna Menon, Ashok Kumar Pandey
##### Design and Analysis of Single Drive Tri-Axis MEMS Gyroscope

MEMS based single and dual-axis gyroscopes have been widely explored for potential application in automotive, space, defense, and consumer electronics sectors. Tri-axis gyroscopes based on MEMS, however, have been sparsely studied. This work presents a novel design for tri-axis MEMS gyroscope and an analytical model to obtain the natural frequencies in drive and sense modes. These frequency values have been compared with the numerically obtained frequencies using Finite Element Analysis (FEA). The analytical results lie within 10% of their numerically obtained values. The frequency matching process involves many iterations of geometric dimensions if the end application requires minor design changes. The proposed analytical model will make the design customization easy as the frequencies of each mode will be expressed as a function of critical geometrical parameters saving multiple numerical runs required for design optimization.

Pradnya Chabbi, Anant Khedkar, Venkatesh K. P. Rao
##### Analysis of the Equilibrium of a Magnetic Contactless Suspension

In this paper a one-dimensional model of magnetic suspension in the case of a variable magnetic field is considered. Analytical expressions for the averaged over a period of an external current source for the suspension equilibrium position are obtained. It is shown that the magnetic stiffness of the suspension has a sign-variable character in the general case. An expression for the averaged value of the magnetic stiffness is obtained and it is shown that this value is always positive.

Pavel Udalov, Alexey Lukin, Ivan Popov, Dmitriy Skubov
##### Frequency Analysis of Microbeam with Axial Pretension Using MSGT

This paper presents the variation in natural frequencies of Euler-Bernoulli microbeams when subjected to axial pretension. The influence of size effects has been analysed using modified strain gradient theory (MSGT). The governing equation of motion has been derived using extended Hamilton’s principle and variational calculus. The sixth order non-local governing differential equation is solved by analytical procedure and numerical differential quadrature method (DQM). The three end conditions of beams are considered: cantilever, simply supported, and clamped-clamped beams. It is found that MSGT accurately models the size effects compared to other theories. As the axial pretension increases from 0.0001 to 1 N, the natural frequency values for the beam with different boundary conditions increase. Subsequently, surface elasticity effects have been analysed for a silicon and aluminium-based nanobeams with the pretension of 0.0001 N for all boundary conditions. From the results of surface elasticity modeling, it has been concluded that the natural frequencies of the nanobeam get influenced either positive or negative based on the value of surface elastic modulus. The difference in natural frequency values with and without surface elasticity effects are approximately 5 and $$2\%$$ for Si and Al nanobeams respectively. The methodology presented in this work can further be validated for nanoscale devices in which the higher-order strain gradient and surface elasticity effects subjected to pretension dominate.

Sai Kishore Jujjuvarapu, Indrasena Reddy Erravelly, Ashok Kumar Pandey
##### Nonlocal Nonlinear Analysis of Functionally Graded Nano Plates Used in MEMs Devices

In this work, an extension of Eringens model for analysis of functionally graded nano plates used in MEMS (micro-electromechanical systems) devices will be presented. Rule of mixtures and Mori-Tanaka methods are adopted for through thickness homogenization of material properties. The role of nonlocal parameter together with the choice of homogenization method is studied in FGM plates. Reddy’s third order shear deformation theory [1] is adopted for the analysis of the plates. The limitations in use of Eringen’s model are also discussed in detail.

##### Finite Element Analysis of Squeezed Film Damping on Trapezoidal Microcantilever Resonators at Different Pressure Levels

Squeezed film damping (SFD) becomes a dominant damping mechanism in micro-electro-mechanical system (MEMS). Depending on the pressure variation in MEMS, SFD governs the dynamic parameters like quality factors (Q factors) and damping ratio. In the present paper, we calculate the Q factor and damping ratio of the trapezoidal shaped microcantilever beam by eigenfrequency analysis using finite element method (FEM) in COMSOL Multiphysics. The effective viscosity method is used to calculate the SFD in FEM for the continuum, slip, transition and molecular flow regimes as described by the Knudsen no. (Kn). Kn is varied by altering the operating pressure, keeping the thickness of air gap constant. It is observed that the Q factor and damping ratio of trapezoidal microcantilever beam varies by an order of million for different flow regimes with the change of operating pressure from atmospheric to 0.1 Pa.

Varun P. Sharma, Rahul Shukla
##### Two-Dimensional Hydrodynamic Forces in an Array of Shape-Morphed Cantilever Beams

In this paper, we estimated the hydrodynamic force in an array of cantilever beams separated by a distance $$\bar{s}$$ oscillating in a viscous fluid. The beam is assumed to be sufficiently long to consider 2D flow and has symmetric as well as asymmetric shape morphing curvature while oscillating in a fluid. The fluid-structure interaction problem is modelled by considering the unsteady Stokes equation. The resulting 1D boundary integral problem is solved by the boundary element method (BEM) numerically in MATLAB to obtain the desired pressure distribution on the beam. It is found that as the frequency oscillation of the rigid beam is increased, both the damping as well as added mass effects are decreased at different rates due to the gradual decrease in unsteady viscous layer. Finally, the hydrodynamic coupling effect on the beam is demonstrated at $$\beta =0.1$$ . However, for increase in the symmetric and asymmetric shape morphing parameters, the hydrodynamic decoupling appears lower than the gap ratio 5. The cantilever beam with optimal shape morphing parameter can be useful for the optimal designs of atomic force microscopy (AFM).

Lalsingh Devsoth, Ashok Kumar Pandey
##### Design and Performance Analysis of TiOx Based MEMS Bolometer Pixel

In this study the electro-thermo-mechanical behavior and analysis of TiOx microbolometer is presented. Different thermal, electrical and coupled electromechanical simulations were performed to achieve the target Noise Equivalent Temperature Difference (NETD) and thermal time constant. The influence of various device dimensions and film thickness on device thermal conductance, NETD and thermal time constant has been reported.

Isha Yadav, Sudha Gupta, A. Vishwakarma, S. Dutta, Ratnamala Chatterjee
##### FEM Analysis of Split Electrode IDTs Designed Lithium Tantalate-Polyaniline SAW Gas Sensor

The finite element method (FEM) underpinning COMSOL Multiphysics 6.0 has been used to model the sensing of various polar volatile organic compounds (VOCs) by the split electrode interdigital transducers (SEIDT) surface acoustic wave (SAW) sensor. On a LiTaO3 base, split-electrode interdigital transducers were employed with a sensing layer of polyaniline (PANI). Acetone VOC gas was detected using a SAW sensor at RT with a concentration of 100 ppm. After the gas specimen interacted with the detecting polymer, a change in the density of the sensing surface was seen, and with it, a change in the Rayleigh wave's Eigen frequency. For a number of studies, we measured admittance, displacement, quality factor, and electric potential versus frequency in addition to plotting the deformed shape at the Eigen (resonance) frequency. The S-parameter and quality factor studies also demonstrate the benefits of using split electrode IDTs in SAW sensors for lowering reflection loss.

Dhananjaya Panda, Koteswara Rao Peta
##### Thermal Study of Thin-Film Heater for PCR Reaction-Based Applications

This paper presents the design, fabrication, and characterization of a thin-film Cr-Al-Cr (300 A°-1500 A°-300 A°) metal stack heater specially designed for chemical reactions which occur at a uniform temperature in the lab on a chip platform such as polymerase chain reaction (PCR) applications. The heater has been designed using COMSOL Multiphysics. The simulated design has been fabricated using lithography and patterning on a 5 × 5 cm2 glass substrate. For the validation of the proposed design thermal study of the fabricated heater has also been done using a FLIR IR camera. A very good agreement between the thermal image of modeled and fabricated heater has been achieved. This demonstrates the suitability of the proposed heater for PCR reaction applications.

Andleeb Zahra, Giampiero de Cesare, Domenico Caputo, Zia Abbas
##### Etching Characteristics of Si{110} in NaOH Based Solution

In the present work, we have studied the etching characteristics of Si{110} in 10M NaOH solution without and with addition of NH2OH. The etch rate of silicon and thermal oxide, and the undercutting rate at convex corners, which are important parameters to be known in the fabrication of MEMS structures using silicon wet bulk micromachining, have been studied in modified NaOH solution. The etch rate of silicon and the undercutting at convex corners increase significantly with the addition of NH2OH, while the etch rate of silicon dioxide reduces considerably with the addition of NH2OH etchant.

Soumya Purohit, Veerla Swarnalatha, Prem Pal
##### Effect of IPA on Micromachining Characteristics of Silicon in KOH-Based Solution

Microstructures for microelectromechanical system (MEMS) applications are widely fabricated using silicon wet bulk micromachining technique. In this method, potassium hydroxide (KOH) is one of the most used anisotropic etchants. It provides high etch rate when it is modified by the addition of hydroxylamine (NH2OH). Moreover, it shows high undercutting which is a desirable property for the fabrication of overhanging microstructures. In this paper, the effect of isopropyl alcohol (IPA) in NH2OH-added KOH on the etching characteristics of Si{100} and Si{110}) is systematically studied. The results are compared with the etching characteristics of IPA-added pure KOH. The undercutting rate reduces drastically when IPA is added to NH2OH + KOH which protects the convex corners of the structures during etching process. At the same time, the etch rate of {110} plane is suppressed considerable which is exploited to expose {110} plane at the mask edges aligned along <100> direction on {100} surface that makes 45° angle with {100} surface and act as a micromirror.

Avvaru Venkata Narasimha Rao, Prem Pal
##### Deep Grooves in Borofloat Glass by Wet Bulk Micromachining

In this work, deep grooves of more than 300 µm depth are fabricated in a high-quality Borofloat glass wafer using wet bulk micromachining in buffered HF (BHF) solution. The Cr/Au/photoresist layers are used as the etching mask. These masking layers showed very good chemical resistance to etching in BHF solution. The etchant provides smooth etched surface morphology with an excellent etch rate of 11.1 µm/min. The proposed process is very useful for the formation of deep grooves with smooth vertical sidewalls and uniform bottom surfaces.

Adarsh Nigam, Swarnalatha Veerla, Prem Pal
##### Micro-piezo Actuator for Cell Lysis

In this study, we demonstrate a piezoelectric actuator for the lysis of bacteria using Travelling Surface Acoustic Waves (TSAWs) produced by gold IDTs (Interdigitated Transducers) fabricated on lithium niobate substrate. We are able to achieve ~99% lysis using IDTs of width 50 μm each, at 19.9 MHz. The developed piezoelectric actuator is a chemical free technology and can be used to lyse any type of bacteria as well as eukaryotic cells.

Sushama Agarwalla, Suhanya Duraiswamy
##### Wax-Printed Microfluidic Paper Analytical Device for Viscosity-Based Biosensing in a 3D Printed Image Analysis Platform

In recent years, several techniques for detecting relative viscosity in the microfluidic environment have been described as having their advantages and limitations. In this context, the present method of microfluidic viscometer provides a very feasible and cost-effective method, in terms of device fabrication detection and analysis. Herein, the hydrophobic patterns of paraffin wax on cellulose paper were created using an inexpensive laminator. In the fabricated microscale paper-based analytical device (µPAD), two points in a microchannel, with pre-defined length, were created and the average time taken for sample fluid to cover this length was leveraged to compute viscosity. These two points in the microchannel were color-coded regions of interest (ROIs) and video frames were captured during the fluid flow across the microchannel. An image processing algorithm with the greyscale alteration in the ROIs was used to compute the time taken by the fluid to cover the two points with known distances. A 3D printed platform, comprising a µPAD, a commercial onboard camera, and an LCD display, was established to implement the image processing mechanism and automate the overall workflow. This inexpensive, user-friendly and adaptable wax lamination technology is an important alternative to existing approaches, and it opens up a world of possibilities for researchers working in resource-strapped labs. Such microfluidic-based viscometers have shown to have great potential for regular monitoring the customized point-of-care (PoC) devices in a regulated and turnkey manner.

Mrunali D. Wagh, S. B. Puneeth, Subhendu Kumar Sahoo, Sanket Goel
##### Detection of Volatile Organic Compounds Using Solution Processed Organic Field-Effect Transistors

We report chemical sensors based on solution processed organic field-effect transistors (OFETs) for detecting volatile organic compounds (VOCs). The OFETs were prepared on flexible plastic substrates and operated at low voltages (≤3 V) with high performance. These OFETs can be used to detect a range of VOCs, including alcohols and ketones. The sensitivity of these devices depends on the polarity of the analytes, and more hydrophobic analytes with longer alkyl chains show higher sensitivities than those with shorter alkyl chains. Arrays of these devices are suitable for portable sensor applications, such as environmental monitoring, food quality monitoring, and medical diagnostics.

Suresh Kumar Garlapati, Sheida Faraji, Daniel Tate, Aiman Rahmanudin, Palaniappan Valliappan, Alessanndro Patti, Krishna Persaud, Michael Turner
##### Thickness Dependent Chlorpyrifos Sensing Behavior of Silver Doped ZnO Nanowires

In this research work, an attempt has been made to grow high aspect ratio zinc oxide nanowires hydrothermally by limited volume heating technique. Silver films of thicknesses ranging from 15 to 45 nm were deposited on nanowires by RF sputtering followed by thermal treatment at drive-in temperature of 475 ℃ in argon ambient. Morphological and structural investigation of nanowires revealed with high aspect ratio around 120 and an average length of 4.5 μm. The interplanar lattice spacing, measured using the high-resolution transmission electron microscope is found to be around 0.26 nm, which corresponds to the wurtzite ZnO. Elemental study depicts homogeneous distribution and co-existence of Zn, O and Ag. X-ray diffraction pattern depicts the evolution of (002) orientation peak, which corresponds to the hexagonal wurtzite structure. Raman spectra displays a prominent peak at 438 cm−1 corresponding to the characteristic nature of wurtzite ZnO with a blue shift at higher drive-in temperature. The chlorpyrifos (CP) sensing study has shown the in/out current ratio around 68 for chlorpyrifos dosage of 3000 mg/kg at an optimized film thickness of 30 nm. The CP response and recovery time constant were found to be around 1.1 s and 1.2 s, respectively.

S. P. Ghosh, D. Pradhan, S. Pattnaik, J. P. Kar
##### Investigation of AuCl3 Doped MoS2 Based IR Detector with the Variation of Annealing Temperature

Low dimensional transition metal dichalcogenides (TMDC) are under current investigation for the fabrication of portable and low cost IR detectors. Among the vast family of TMDC, molybdenum disulphide (MoS2) has been considered as a potential candidate for the next-generation IR detectors due to its outstanding properties. In this research, MoS2 thin films were grown by rapid thermal process at an elevated temperature for a shorter duration with the flow of inert (argon) and reducing (hydrogen) gas. In order to modulate the post-growth characteristics of MoS2 films, spin coated AuCl3 layer was used as a source of p-type dopant. Thereafter, rapid thermal annealing of the AuCl3 treated MoS2 films was carried out at various temperatures ranging from 200 °C to 500 °C. FESEM images have revealed the modulation in the morphology beyond 300 °C. XRD studies depicted the appearance of (002) characteristic peak, whose intensity was found to be increased with annealing temperature up to 300 °C. Raman spectra have shown the evolution of E12g and A1g active mode peaks. The Raman peak position was found to be shifted with the variation in post-treatment annealing temperature. Using Mott-Schottky analysis, the dependence of carrier concentration of MoS2 films and built-in potential across MoS2/Si heterojunction on the annealing temperature were estimated. The ideality factor of MoS2/Si heterojunction was investigated from current-voltage characteristics. The IR detection behaviour of MoS2/Si heterojunction was studied.

Diana Pradhan, Anurag Gartia, Kiran K. Sahoo, Surya P. Ghosh, Jyoti P. Kar
##### Investigation of Structural and Electrical Properties of Ta2O5 Thin Films with Sputtering Parameters for Microelectronic Applications

Tantalum oxide (Ta2O5) thin film is considered as an alternative dielectric layer in both microelectronics and MEMS devices due to its high dielectric constant, high breakdown field and low leakage current density. In this research, radio-frequency magnetron sputtering was used to deposit Ta2O5 thin films on p-type Si (100) substrates. During the film deposition, the RF power and Ar/O2 gas flow ratio were kept constant while the sputtering pressure and substrate temperature were varied. The films were annealed in the air for an hour at 900 ℃ after the deposition. The structural, morphological, and electrical properties of the films were studied with various sputtering parameters. Orthorhombic β—phase structure of Ta2O5 films is observed from XRD investigation. The crystallinity of the films was found to be improved with the increase in the sputtering pressure and substrate temperature. The films, deposited at higher working pressure, became rough, whereas the films deposited at higher temperature became smooth. The Capacitance-voltage and current-voltage techniques were used to study the electrical properties of the thin films. Low oxide charge density of 6.5 × 1011 cm−2 and 3.1 × 1012 cm−2 observed at sputtering pressure of 8.0 × 10–3 mbar and substrate temperature of 300 ℃, respectively.

Kiran K. Sahoo, D. Pradhan, S. P. Ghosh, A. Gartia, J. P. Kar
##### Optimization of Controllable Pulsed LASER Deposition Parameters for the Fabrication of Lead Free Ba(Zr0.15Ti0.85)O3 Thin Films

Owing to the superior energy and power storage properties, the Zr doped BaTiO3 (BZT) material system is reportedly used in numerous applications. In this work, the optimal process parameters viz., substrate temperature, oxygen gas pressure, laser fluence and target-substrate distance for deposition of lead-free thin films using pulsed laser deposition (PLD) system were evaluated. The deposition of BZT thin films were carried out based on design of experiments by adopting the Taguchi method. The thickness and dielectric properties of deposited thin films were analyzed to assess the influence of each parameter on the growth of thin films using analysis of variance (ANOVA) method. Optimal process conditions based on grey relational analysis were evaluated. The phase and morphology analysis on BZT films indicate possibility of domain engineering by choosing appropriate process variables. BZT thin films deposited at optimal process conditions resulted in superior properties comparable to properties of single crystal of the same material system.

M. L. V. Mahesh, Prem Pal, V. V. Bhanuprasad, A. R. James
##### Resistive Switching Behavior of TiO Nanostructures Grown by Dip Coating Process

In recent years, titanium dioxide (TiO $$_{2}$$ ) has drawn tremendous attentions due to its excellent electronic properties, nontoxic nature, high chemical stability, low cost, and huge availability in nature. TiO $$_{2}$$ nanostructures were grown on boron doped, (100) oriented, 1–10 $$\Omega$$ -cm silicon substrates by using wet chemical method, where the concentration of titanium n-butoxide was varied from 0.24 ml to 0.60 ml. The chemical process was conducted at 140 $$^\circ$$ C for 2 h using an autoclave. The morphological and structural properties of TiO $$_{2}$$ nanostructures were investigated by scanning electron microscope (SEM) and X-ray Diffraction (XRD) techniques. The nano flowers like structures were observed by the SEM study and rutile phase of TiO $$_{2}$$ was depicted by the XRD analysis. The nanostructures were increasing with the titanium butoxide concentration that was confirmed by SEM study. In precursor concentration of 0.60 ml, the nanostructures of width 256 nm and length 1.54 $$\mu$$ m were obtained. Resistive switching study was showing the memory capacity of the nanorod structures.

S. Roy, P. K. Sahu, D. Pradhan, N. Tripathy, J. P. Kar
Titel
Microactuators, Microsensors and Micromechanisms
herausgegeben von
Ashok Kumar Pandey
Prem Pal
Nagahanumaiah
Lena Zentner