Miniaturization of PCR Machine

The polymerase chain reaction (PCR) is a technique defined for copying specific DNA sequences. The three basic steps in that process - splitting a DNA template into its two single strands (called denaturation); adding short segments of complementary DNA called primers to initiate replication of a chosen DNA sequence (annealing); and adding DNA polymerase to synthesis the complementary strand (called extension) - are repeated again and again to amplify the sequence. Each of these steps occurs optimally at a different temperature, so heating and cooling is carried out with an instrument called a thermal cycler. Better than the conventional big size PCR here we have designed a circuit which is capable of performing fast temperature rise and fall and that is within small region. This design supports the easy transportability of the machine because of its smaller size with very low design cost

Fabrication of micro separation column for miniaturized gas chromatography system

The emphasis of this work is on the fabrication of a micro separation column for applicaton in miniaturized gas chromatography system. The micro column was made by microchannels fabricated on the silicon wafer and sealed with a glass lid. The microchannels were fabricated by wet etching process and the channels were of length 2m , width 200 μm and depth 100 μm. The channels were closed by sealing with Pyrex glass. Silicide bonding was done for the bonding of silicon with Pyrex glass. Ti was used as an intermediate layer and bonded at a temperature of 377 ◦C and a force of 1kN. During bonding Ti forms an alloy with silicon and forms Titanium silicide and this helps to bond the glass wafer with silicom wafer with microchannels etched on it

Measurement and modeling of pulsatile flow in microchannel

An experimental study of pulsatile flow in microchannel is reported in this paper. Such a study is important because time-varying flows are frequently encountered in microdevices. The hydraulic diameter of the microchannel is 144 μm and deionized water is the working fluid. The pressure drop across the microchannel as a function of time is recorded, from which the average and r.m.s. pressure drops are obtained. The experiments have been performed in the quasi-steady flow regime for a wide range of flow rate, frequency of pulsations, and duty cycle. The results suggest that the pressure with pulsations lies between the minimum and maximum steady state pressure values. The average pressure drop with pulsation is approximately linear with respect to the flow rate. The theoretical expression for pressure has also been derived wherever possible and the experimental data is found to lie below the corresponding theoretical values. The difference with respect to the theoretical value increases with an increase in frequency and a decrease in flow rate, with a maximum difference of 32.7%. This is attributed to the small size of the microchannel. An increase in frequency of square waveform leads to a larger reduction in pressure drop as compared to rectangular waveform, irrespective of the duty cycle. The results can be interpreted with the help of a first-order model proposed here; the model results are found to compare well against the experimental results. A correlation for friction factor in terms of the other non-dimensional governing parameters is also proposed. Experimental study of mass-driven pulsatile flow in microchannel is being conducted for the first time at these scales and the results are of both fundamental and practical importance

Three-Dimensional Numerical Study of Conjugate Heat Transfer in Diverging Microchannel

Increase in applications of varying cross sectional area microchannels in microdevices has provided the need to understand fluid flow and heat transfer through such flow passages. This study focuses on conjugate heat transfer study through a diverging microchannel. Three-dimensional numerical simulations are performed using commercially available package. Diverging microchannels with different geometrical configurations (i.e. varying angle: 1-8°, depth: 86-200 μm, solid-to- fluid thickness ratio: 1.5-4) are employed for this purpose. Simulations are carried out for varying mass flow rate (3.3 x 10 –5 -8.3 x 10 –5 kg/s) and heat flux (2.4-9.6 W/cm 2 ) conditions. Heat distribution along the flow direction is studied to understand the effect of wall conduction. Wall conduction number ( M ) varies from 0.006 to 0.024 for the range of parameters selected in the study. Wall conduction is observed to be a direct function of depth and solid-to-fluid thickness ratio, and varies inversely with angle of diverging microchannel. It is observed that the area variation and wall conduction contribute separately towards redistribution of the supplied heat flux. This leads to reduced temperature gradients in diverging microchannel. The results presented in this work will be useful for designing future microdevices involving heating or coolin

Highly sensitive and ultra-fast responsive ammonia gas sensor based on 2D ZnO nanoflakes

Detecting ammonia in ambient air with high sensitivity and ultra-fast responsivity is crucial given its implications on human health. The response of such sensors should also be reversible to use them for continuous monitoring. Herein, we report a reversible ammonia (NH3) sensor based on 2D ZnO nanoflakes at 250 °C. The sensor exhibited a maximum response of 80% and sub-15 s response and recovery times upon exposure of 0.6–3 ppm NH3. Further, we formulated and corrected the baseline drift with a simple and straightforward baseline manipulation method. The excellent response of the sensor indicates the feasibility of using it in diverse applications where high sensitivity and rapid response are crucial. © 202

Design, Process Development and Fabrication of SU-8 based CMOS Compatible Capacitive MEMS Platform for Bio-sensing Applications

Bio sensors are integrated devices which could provide information about the composition of Biological samples (semi) quantitatively. The key element of Bio sensors are their transducers which are usually Micro or Nano scale structures with Biological recognition elements as part of them. Realization of a practical and usable Bio sensor involves a wide range of interdisciplinary activities. The emerging interdisciplinary fields of Nanotechnology and Nano fabrication has helped the heterogeneous integration of Biology with Engineering systems which was not possible earlier

Stress analysis in 3D IC having Thermal Through Silicon Vias (TTSV)

TTSV is proposed for the removal of heat from between the IC layers as these TTSVs carries heat down to the sink. However, it may generate stress in Silicon. In the present paper, thermal-stress simulation of stack consists of three IC layers bonded face up is performed using finite element modeling tools. We also analyzed the stress generated in 3D IC containing TTSV. Further we proposed a method for lower stress around the TTSV. The method proposed decreases the Von Misses Stress by a value of 40Mpa on average considering all the IC layers. Thus by achieving this, functionality of the chip becomes more reliable

DP-fill: a dynamic programming approach to X-filling for minimizing peak test power in scan tests

At-speed testing is crucial to catch small delay defects that occur during the manufacture of high performance digital chips. Launch-Off-Capture (LOC) and Launch-Off-Shift (LOS) are two prevalently used schemes for this purpose. LOS scheme achieves higher fault coverage while consuming lesser test time over LOC scheme, but dissipates higher power during the capture phase of the at-speed test. Excessive IR-drop during capture phase on the power grid causes false delay failures leading to significant yield reduction that is unwarranted. As reported in literature, an intelligent filling of don't care bits (X-filling) in test cubes has yielded significant power reduction. Given that the tests output by automatic test pattern generation (ATPG) tools for big circuits have large number of don't care bits, the X-filling technique is very effective for them. Assuming that the design for testability (DFT) scheme preserves the state of the combinational logic between capture phases of successive patterns, this paper maps the problem of optimal X-filling for peak power minimization during LOS scheme to a variant of interval coloring problem and proposes a dynamic programming (DP) algorithm for the same along with a theoretical proof for its optimality. To the best of our knowledge, this is the first ever reported X-filling algorithm that is optimal. The proposed algorithm when experimented on ITC99 benchmarks produced peak power savings of up to 34% over the best known low power X-filling algorithm for LOS testing. Interestingly, it is observed that the power savings increase with the size of the circuit

A low/high band highly linearized reconfigurable down conversion mixer in 65nm CMOS process

This paper presents a universal down conversion mixer for a multistandard wireless receiver with adapted reconfigurability in the form of RF bandwidth, active/passive and IF bandwidth. In the proposed architecture RF bandwidth reconfigurability is reconfigured between low band (LB) RF frequency and high band (HB) RF frequency mixer modes. LB / HB reconfigurability is made through power switching the transconductance amplifier. Active / Passive reconfigurability is made through switching the input signal between gate and source terminal of input transistors and enabling/disabling the transimpedance stage at the output. The CMOS transmission gate (TG) switches are designed to provide optimum headroom in this low voltage design. The proposed circuit is designed in the UMC 65nm RFCMOS technology with 1.2V supply voltage. From the simulation results, the proposed circuit shows conversion gain of 22/26 dB and 25/31 dB, noise figure of 14.2/12.1 dB and 11.5/8.16 dB, IIP3 of 10/8.1 dBm and 6.4/3 dBm in LB and HB respectively where all these figures suggest passive/active mode. Hence this circuit will be much helpful in multi-standard receiver design