Drago Strle

Sensitivity Comparison of Vapor Trace Detection of Explosives Based on Chemo-Mechanical Sensing with Optical Detection and Capacitive Sensing with Electronic Detection

The article offers a comparison of the sensitivities for vapour trace detection of Trinitrotoluene (TNT) explosives of two different sensor systems: a chemo-mechanical sensor based on chemically modified Atomic Force Microscope (AFM) cantilevers based on Micro Electro Mechanical System (MEMS) technology with optical detection (CMO), and a miniature system based on capacitive detection of chemically functionalized planar capacitors with interdigitated electrodes with a comb-like structure with electronic detection (CE). In both cases (either CMO or CE), the sensor surfaces are chemically functionalized with a layer of APhS (trimethoxyphenylsilane) molecules, which give the strongest sensor response for TNT. The construction and calibration of a vapour generator is also presented. The measurements of the sensor response to TNT are performed under equal conditions for both systems, and the results show that CE system with ultrasensitive electronics is far superior to optical detection using MEMS. Using CMO system, we can detect 300 molecules of TNT in 10+12 molecules of N2 carrier gas, whereas the CE system can detect three molecules of TNT in 10+12 molecules of carrier N2.

Surface-Functionalized COMB Capacitive Sensors and CMOS Electronics for Vapor Trace Detection of Explosives

In this paper, we present a miniature detection system, which is able to detect and selectively recognize different vapor traces of explosives. It is based on surface-functionalized array of COMB capacitive sensors and extremely low noise integrated electronics. The measurement system is sensitive and selective, consumes minimum amount of energy, is very small and cheap to produce in large quantities, and is insensitive to environmental influences. Owing to extremely low noise electronics and selective modification of COMB capacitor surfaces, it is possible to detect less than 3.5 ppt of TNT in the atmosphere (three TNT molecules in 10+12 molecules of air and 10 times better for RDX) at 25°C in one second using very small volume (few mm3). The measurement system needs only approximately 20 mA current at 5 V supply voltage.

An approximate logarithmic squaring circuit with error compensation for DSP applications

The squaring function is one of the frequently used arithmetic functions in DSP, so an approximation of the squaring function is acceptable as long as this approximation corrupts the bits that are already corrupted by noise, and does not degrade application@?s performance significantly. Approximation of the squaring function can lead to significant savings in hardware and processing time. Previously proposed approximations of the squaring function include LUT-based solutions, linear interpolation of the squaring function and minimization of combinational logic. This paper proposes approximation based on a simple logarithmic interpolation of a squaring function with a simple logic block, which can be reused for the error compensation. The proposed block performs approximation of the squaring function with a shift operation and a carry-free subtraction. The proposed approximate squarer with one compensation block achieves the average relative error below 1.5% for any bit length, while maintaining a low power consumption. In order to evaluate the device utilization, the propagation delay and power consumption and to compare it with the existing solutions, we have synthesized the proposed squarer and the existing solutions for the standard cell library and 0.25@mm CMOS process parameters.

Chemical Selectivity and Sensitivity of a 16-Channel Electronic Nose for Trace Vapour Detection

Good chemical selectivity of sensors for detecting vapour traces of targeted molecules is vital to reliable detection systems for explosives and other harmful materials. We present the design, construction and measurements of the electronic response of a 16 channel electronic nose based on 16 differential microcapacitors, which were surface-functionalized by different silanes. The e-nose detects less than 1 molecule of TNT out of 10+12 N2 molecules in a carrier gas in 1 s. Differently silanized sensors give different responses to different molecules. Electronic responses are presented for TNT, RDX, DNT, H2S, HCN, FeS, NH3, propane, methanol, acetone, ethanol, methane, toluene and water. We consider the number density of these molecules and find that silane surfaces show extreme affinity for attracting molecules of TNT, DNT and RDX. The probability to bind these molecules and form a surface-adsorbate is typically 10+7 times larger than the probability to bind water molecules, for example. We present a matrix of responses of differently functionalized microcapacitors and we propose that chemical selectivity of multichannel e-nose could be enhanced by using artificial intelligence deep learning methods.

Detecting vapor traces of explosives using a self-assembled mono layer on a surface-modified MEMS capacitor and CMOS electronics

A miniature detection system, which is able to detect and selectively recognize different vapour traces of explosives, is presented in this article. It is based on surface-functionalised MEMS capacitive sensors and an extremely low noise integrated circuit. The instrument is sensitive and selective, consumes a minimum amount of energy, is very small and cheap to produce in large quantities, and is insensitive to mechanical influences. It is possible to detect 3ppt of TNT in the atmosphere (3 TNT molecules in 10+12 molecules of air) at 25 °C in 1 Hz bandwidth using very small volume (few mm3) and only approx 20 mA current from a 5 V supply voltage.

Integrated impedance spectroscopy chip for bio-sensors array: A system perspective

System design issues for an integrated impedance spectroscopy measurement system that can be used to measure the impedance of an electrode-electrolyte interface caused by bio-chemical interface for the array of biosensors are discussed in this work. Using the approach presented in this article, it is possible to measure the spatial and temporal distribution of bio-chemical interactions caused by in vitro activity of a slice of the neurons in real time. Standard instrumentation cannot be used for such measurements because of the many instruments needed, disturbances caused by long connecting wires, parasitic capacitances and resistances, and high cost, therefore, a miniaturized, integrated array of instruments is needed. In this article, we describe and evaluate possible different approaches, system design issues, and possible limitations for such an integrated impedance spectroscopy instrument.

Modeling, simulations and design of mems electromechanical sigma-delta modulator

In this article we present part of the design methodology, modeling and efficient simulation of high performance micro-electromechanical ΣΔ modulator used for MEMS accelerometer. The method is based on converting continuous-time model of the MEMS sensor and eventual analog loop filter into discrete time equivalent using impulse invariant transformation. The methodology is valid for any “MEMS based cantilever” sensor operating in a closed loop, where mechanical transfer function does not provide adequate noise shaping to reach high accuracy and resolution. Using proposed methodology makes possible to efficiently design, predict the behavior and stability of the loop and perform efficient system level simulations.

Capacitor-based detection of nuclear magnetization: Nuclear quadrupole resonance of surfaces

We demonstrate excitation and detection of nuclear magnetization in a nuclear quadrupole resonance (NQR) experiment with a parallel plate capacitor, where the sample is located between the two capacitor plates and not in a coil as usually. While the sensitivity of this capacitor-based detection is found lower compared to an optimal coil-based detection of the same amount of sample, it becomes comparable in the case of very thin samples and even advantageous in the proximity of conducting bodies. This capacitor-based setup may find its application in acquisition of NQR signals from the surface layers on conducting bodies or in a portable tightly integrated nuclear magnetic resonance sensor.

Efficient testing of Σ-Δ A/D converters

In this paper we discuss a possibility to simplify and speed up testing of high-resolution SigmaDelta modulators. The methodology could be used for production testing as well as for real time built-in self-tests. We show that a pseudo-random signal is a good option for a signal source and that test method leads to efficient and cost-effective production testing that can also be used for real time built-in self-tests. The method is theoretically analyzed and verified using Matlab simulations. The models of DUT and reference digital circuits are simulated and the difference is demonstrated with simple area-efficient algorithm/hardware.

Low voltage, low power 13-bit linear voice codec with programmable analogue frontend

A low-voltage, low-power 13-bit linear voice codec has been developed and implemented in 1.2 /spl mu/m CMOS technology. At single supply voltage greater than 2.6 V and power dissipation of 20 mW it fulfils or exceeds all NET33 recommendations for digital handset terminals. Active area for a complete codec is 29 mm/sup 2/. It can be used as an analogue frontend for DSP, digital cordless telephone, a digital cellular telephone or a digital answering machine.<<ETX>>