nan Nagahanumaiah

Silver Nanoparticles in Comparison with Ionic Liquid and rGO as Gate Dopant for Paper–Pencil-Based Flexible Field-Effect Transistors

Nanoparticle-based flexible field-effect transistors (FETs) containing carbon nanotubes (CNTs) and silicon nanowires (SiNWs) have attracted tremendous attention, since their interesting device performance can be utilized for integrated nanoscale electronics. However, use of CNTs and SiNWs on polymer substrates poses serious limitations in terms of their fabrication procedure, repeatability, and biodegradability. In this article, we report for the first time the fabrication and characteristics of solution-processed FETs on a paper substrate doped with easily prepared silver nanoparticles (AgNPs). To compare the FET performance, we fabricated two other FETs on paper containing ionic liquid (IL, 1-butyl-3-methylimidazolium octyl sulfate) and reduced graphene oxide (rGO) as dopants. We observe that the AgNP-based dopant generated good FET characteristics in terms of linear transconductance variations and higher carrier concentration values, showing negligible changes after bending and aging. In comparison with the AgNP-FET, the rGO- and IL-based dopants yielded high carrier mobilities, but the rGO-based FET is more susceptible to aging and bending. The excellent linearity of the IDS–VG curve found for the AgNP-FET ensures its applicability for devices requiring linear transfer characteristics such as linear amplifiers.

A novel approach to fabricate dye-encapsulated polymeric micro- and nanoparticles by thin film dewetting technique

A new method is reported for fabrication of polymeric micro- and nanoparticles from an intermediate patterned surface originated by dewetting of a polymeric thin film. Poly (d, l-lactide-co-glycolide) or PLGA, a biocompatible polymer is used to develop a thin film over a clean glass substrate which dewets spontaneously in the micro-/nano-patterned surface of size range 50nm to 3.5µm. Since another water-soluble polymer, poly vinyl alcohol (PVA) is coated on the same glass substrate before PLGA thin film formation, developed micro-/nano-patterns are easily extracted in water in the form of micro- and nanoparticle mixture of size range 50nm to 3.0µm. This simplified method is also used to effectively encapsulate a dye molecule, rhodamine B inside the PLGA micro-/nanoparticles. The developed dye-encapsulated nanoparticles, PLGA-rhodamine are separated from the mixture and tested for in-vitro delivery application of external molecules inside human lung cancer cells. For the first time, the use of thin film dewetting technique is reported as a potential route for the synthesis of polymeric micro-/nanoparticles and effective encapsulation of external species therein.

Tool strain–based wear estimation in micro turning using Bayesian networks

Estimation of tool wear in micro turning is important as it enhances the process fidelity and the surface quality of the job. In this work, a simple process is demonstrated that estimates the tool wear from strain data near the cutting edge of the tool tip for micro turning operations. The tool strain for tool with six different wear lengths, collected using fiber Bragg grating sensor, was preprocessed to generate a probability distribution. The strain and tool wear data were used as the training dataset. This training dataset was subjected to maximum likelihood estimation algorithm to obtain the conditional probability distribution table required for the functioning of a suitable Bayesian network. The Bayesian network was tested for estimation of tool wear using strain data as priors for three different experiments. The maximum error in tool wear estimation using this procedure was ∼6 µm.

Dynamic Shear Stress Evaluation on Micro-Turning Tool Using Photoelasticity

The paper presents an experimental methodology for evaluation of shear stress induced on a micro-turning tool during micro-turning operation. A micro-turning tool manufactured by Sandvik Coromant was used for micro- turning of a brass spindle. The front face of the tool was cleaned, polished and coated with a thin layer of Ethylene-Vinyl Acetate (EVA), a birefringent material. Subsequently, reflection photoelastic experiments were conducted to find the shear stresses induced on the micro-tool. A custom designed grey field poledioscope was used for this purpose which was pre-calibrated and verified using disk under compression test. The tool was subjected to turning operation and dynamic images of the tool were captured using Casio ELIXIM ZR-200 camera in high speed movie mode at 1000 fps (frames per second) for four different orientations of the analyzer simultaneously. These images were processed using a code developed in MATLAB software to generate a shear stress map of the tool dynamically at different time instants of the machining process.

Polymeric-Patterned Surface for Biomedical Applications

Polymeric-patterned surfaces are finding significant importance in various biomedical applications such as screening and diagnostic assays, tissue engineering, biosensors, and in the study of fundamental cell biology. A wide variety of methods, involving photolithography, inkjet printing, soft lithography, and dip-pen lithography, have emerged for protein or polymer patterning on various substrates. For directional immobilization or adsorption of protein, surface requires pre-defined regions to which protein molecules can be immobilized. The most common techniques to introduce defined protein immobilization are soft lithography and photolithography. However, these techniques have some associated limitations. In soft lithography, stamps with well-defined structures are required, and the migration of ink during and after printing needs to be well controlled. In photolithography, a polymeric photoresist and a mask are needed which require expensive setup to fabricate. Therefore, facile and economic techniques are worth exploring. The dewetting of a thin polymeric film is a spontaneous and self-organized process that forms an array of microscale and nanoscale droplets on a substrate. This is a facile approach of patterning polymer on glass substrate providing a reliable surface for specific, dense, and uniform immobilization of desired molecules to pre-designed patterns. Since antibody orientation is very important in antibody-based surface capture assays, patterned polymer surfaces are of great importance with respect to an increasing number of biosensor applications. Apart from protein patterning, such polymeric-patterned surface can be effectively used in specific type of cell isolation and detection. Indeed, it is found that circulating tumor cells (CTCs) are easily isolated using such patterned structures either on a flat plate or inside a microfluidic environment.

Analysis of Surface Texture of High Aspect Ratio Blind Micro Holes on Titanium Alloy (Ti-6Al-4V) in Micro Electrical Discharge Drilling

Efficiency of any machining process depends on the effectiveness of final outcomes. Surface integrity plays an important role in functional performance of a part or component. Traditionally, surface roughness is considered to be the principal parameter to assess the surface integrity of a machined surface. In this paper, the influences of machining parameters like gap voltage, capacitance and depth of hole on the surface finish parameters like Ra and Sa of micro holes have been studied in micro electrical discharge drilling. The high aspect ratio blind micro holes were drilled on titanium alloy (Ti-6Al-4V) with cylindrical tungsten tool electrodes. The experimentation was carried out adopting a full factorial design (33). The simultaneous effects of machining parameters on responses were analysed using response surface methodology. Multiple linear regression models were developed for responses to obtain the correlation between machining parameters and machining outputs. Multi-objective optimization has been performed with the aid of the desirability function approach.

Time-varying process model for intelligent prediction of strain and temperature in micro-turning process

Time-varying process models for micro-machining processes are important as they aid in control of machining parameters. In this research, a state-space-based process model for the temperature and strain generated near the cutting edge of the tool tip is identified using system identification approach. Fiber Bragg grating sensors were placed rigidly near the cutting edge of the tool tip in a micro-turning setup. Subsequently, micro-turning operations were carried out on aluminum and mild steel. The computer numerically controlled program was such that the machining parameters (feed velocity, depth of cut and RPM) change with machining time. The time-varying machining parameters act as inputs to the model, and the dynamic values of strain and temperature serve as model output. A state-space model was generated using the experimental data. Subsequently, a Kalman filter was used to intelligently predict the values of strain and temperature at the cutting edge of tool tip in advance using the model parameters identified by state-space modeling. Experimental results confirm that the time-varying model and the Kalman filter proposed in this research are effective in predicting the strain and temperature in advance with high accuracy. The maximum error in prediction of temperature was 0.4 °C, whereas for strain prediction, the maximum error was 0.3µ∈.

Silver and molybdenum disulfide nanoparticles synthesized in situ in dimethylformamide as dielectric for micro-electro discharge machining

The research focuses on the applicability of silver (Ag) and molybdenum disulfide (MOS2) nanoparticle synthesized in situ in dimethylformamide solution as dielectric material for micro-electro discharge machining. Ag nanoparticles (~120 nm size) and MOS2 nanoparticles (~20 nm size) were synthesized in dimethylformamide solution using a combination of nanoparticle solution synthesis routes. A setup for micro-electro discharge machining was developed in-house with an arrangement to generate spark at varying voltages. The setup was integrated with a precise linear height gauge to measure the spark gap during the experiments where Ag and MOS2 nanoparticles in dimethylformamide solution served as dielectric. The debris was collected and was characterized for each of the experiments. The feature size of the crater generated during the micro-electro discharge machining was also studied. The experiments were repeated with silver and MOS2 nanoparticle powder mixed with dimethylformamide as dielectric. It was observed that in situ prepared nanoparticles in dimethylformamide offered much better machining performance in terms of process stability, crater size and material removal rates. On use of in situ synthesized nanoparticle dielectric, the material removal rate increased by nearly two to three times whereas the spark gap increased by about two times.

Stability Analysis of Semi-kinematic Mountings used in Modular Reconfigurable Micro Factory Testbed

In this paper three groove semi kinematic mounting has been designed and analyzed its the stability in micro milling operational conditions, employed in a specific modular reconfigurable micro factory test bed developed at authors group. While various kinds of kinematic couplings, which are popular for their high repeatability and interchangeability, are considered for the modular machine design, Gothic arch and Maxwell coupling designs were compared. In this evaluation process, first the maximum preload, which can resist the induced contact stresses, is determined. Then the static stiffness matrices are evaluated for each case and compared as a measure of their relative stability. Maxwell coupling which was found to be best was adopted for the machine stage and experiments were performed to know the coupling stability with varying load.

A low cost wavelength sensor using dual layer photodiode

Wavelength sensing using ultra low cost electronic circuits is a prime demand in numerous industrial systems. This work proposes an approach towards wavelength sensing in fiber optic devices using a dual layer/ dual wavelength photodiode. A dual wavelength photodiode WS-7.56-TO5 manufactured by Pacific Silicon sensor was used for this application. One of the layers of the photodiode has peak responsivity at 550 nm wavelength and the other one has peak responsivity at 880 nm wavelength. Fiber coupling for the photodiode was conducted which houses a lens assembly in order to concentrate the light incident on the effective sensing area of the photodiode. The associated electronic circuitry consists of a logarithmic ratio amplifier with variable gain and a thermal sensor. Temperature compensation for the photodiode was conducted during calibration using the outputs of thermal sensor. The circuit outputs voltage signal which varies almost linearly with varying wavelength. The circuit was tested for its wavelength sensing efficacy both for peak wavelength in case of monochromatic source and mean wavelength for broadband source. Good variation in output voltage was observed during testing the set up using different single and broadband wavelength sources.