An Electronic-Nose Sensor Node Based on a Polymer-Coated Surface Acoustic Wave Array for Wireless Sensor Network Applications

This study developed an electronic-nose sensor node based on a polymer-coated surface acoustic wave (SAW) sensor array. The sensor node comprised an SAW sensor array, a frequency readout circuit, and an Octopus II wireless module. The sensor array was fabricated on a large K2 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT) was produced with a Cr/Au film as its metallic structure. A mixed-mode frequency readout application specific integrated circuit (ASIC) was fabricated using a TSMC 0.18 μm process. The ASIC output was connected to a wireless module to transmit sensor data to a base station for data storage and analysis. This sensor node is applicable for wireless sensor network (WSN) applications

Particle Sensor Using Solidly Mounted Resonators

This paper describes the development of a novel particle sensing system employing zinc oxide based solidly mounted resonator (SMR) devices for the detection of airborne fine particles (i.e., PM2.5 and PM10). The system operates in a dual configuration in which two SMR devices are driven by Colpitts-type oscillators in a differential mode. Particles are detected by the frequency shift caused by the mass of particles present on one resonator with while the other acts as a reference channel. Experimental validation of the system was performed inside an environmental chamber using a dust generator with the particles of known size and concentration. A sensor sensitivity of 4.6 Hz per μg/m3 was demonstrated for the SMRs resonating at a frequency of 970 MHz. Our results demonstrate that the SMR-based system has the potential to be implemented in CMOS technology as a low-cost, miniature smart particle detector for the real-time monitoring of airborne particles

High frequency surface acoustic wave resonator-based sensor for particulate matter detection

This paper describes the characterization of high frequency Surface Acoustic Wave Resonator-based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as a reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent SAWR sensitivity to be tailored to the size of particles, thus making these types of sensors good candidates for PM10, PM2.5 and ultrafine particle (UFP) detection. Our initial characterisation demonstrated a typical SAWR frequency shift of 60 Hz in response to a deposition of ca. 0.21 ng of 0.75 μm-sized gold particles (∼50 particles) on sensor’s surface. Sensor responses to different size particles, such as ∼30 μm diameter silicon, gold (diameters of ∼0.75 μm and ∼20 μm), ∼8 μm fine sugar, PTFE (∼1 μm and ∼15 μm), ∼4 μm talcum powder, and ∼2 μm molybdenum powder were evaluated, and an average mass sensitivity of 275 Hz/ng was obtained. Based on the results obtained in this study we believe that acoustic wave technology has great potential for application in airborne particle detection. Moreover, acoustic resonator devices can be integrated with CMOS interface circuitry to obtain sensitive, robust, low-power and low-cost particle detectors for variety of applications including outdoor environmental monitoring

Field Programmable Gate Array based Readout for Surface Acoustic Wave Portable Gas Detector

Surface acoustic wave (SAW) is one of the most promising technology in the field of gas sensing at low concentrations. Field deployable portable SAW detectors are, however, prone to noise, there by limiting the detection at low concentrations. To meet the current requirements of gas detection at low concentrations, the readout methodology needs to be based on minimal hardware and better noise management. In this paper we describe a readout scheme for portable SAW gas detectors incorporating a field programmable gate array (FPGA). The developed readout system includes a modified reciprocal frequency counter for differential SAW sensor, median noise filtering and moving averages smoothing for noise management, peak detection and interfacing with external display, all implemented in FPGA. The developed readout was tested against VOCs using a lab developed vapour generator and the results have been presented in the paper. The readout system is compact, low power consuming and expandable through software thus ideal for portable handheld applications

CMOS compatible solidly mounted resonator for air quality monitoring

Air pollution has become a growing concern around the world. Human exposure to hazardous air pollutants is associated with a range of health problems and increased mortality. An estimated 40,000 early deaths per year are caused by the exposure to air pollutants in the UK alone, which cost over £20 billion annually to individuals and health services1. In this work, novel solidly mounted resonator (SMR) devices were developed for integration in a low-cost, portable air quality monitor for the real-time monitoring of particulate matter and volatile organic compounds (VOCs). Finite element models of the SMRs were developed to aid their design and simulate the response of the sensors to particles and exposure to VOCs. For particle sensing, a SMR based unit was developed, working in a dual mode configuration. The unit was characterised inside an environmental chamber, together with commercial reference instruments, to particles of known size and composition. A detection limit of 20 μg/m3 was found (below the safe exposure limit). To target fine particles (<2.5 μm), a virtual impactor was incorporated into the system. For VOC detection, the SMR devices were functionalised with polymer coatings to detect acetone and toluene vapours (most common VOCs in air). A polymer drop-coating system was developed to complete this aim (polymer film thicknesses <100nm). An automated VOC test station was developed to characterise the SMR based sensors to low ppm concentrations of the target vapours (<200 ppm). The SMR devices demonstrated a limit of detection of 5 ppm to toluene and 50 ppm of acetone (well below the safe exposure limits). A novel CMOS based SMR device, suitable for volume production and monolithic integration, was designed with an integrated microheater and CMOS acoustic mirror. The heater was included to vary the temperature of the sensing area (to enhance the sensitivity of the SMR to a particular VOC through temperature modulation or to clear particles off the surface). The fabricated device (1.9 GHz) exhibited good performance

Towards a cell-based chemo receiver for artificial insect olfaction

Infochemical communication is ubiquitous amongst all living organisms, and particularly important in insects. Because smell being the most common basic means of chemical communication, infochemical blends must be constantly decoded in order to proclaim their readiness to mate, to mark out territorial boundaries, to warn off intruders and predators or, in some cases, to locate food or predators with millisecond precision. The central challenge of the thesis was to mimic nature in both cellular and molecular levels on to a technological platform that aids in the development of a new class of technology employing chemicals alone to communicate over space and time. This thesis describes a body of work conducted in the development of a miniaturised, smart and label-free cell-based chemoreceiver for artificial insect olfaction, as part of the development of a novel biomimetic infochemical communication system. A surface acoustic wave based microsensor has been utilized to engineer and develop a chemoreceiver system that mimics the cellular and molecular mechanisms occurring during infochemical detection and decoding in insects. Successful recovery of ratiometric information with the aid of polymer-based gas-phase measurements, established the concept of chemical communication. Thus, small scale, high-throughput infochemical communication has been realized by a combination of precise spatiotemporal signal generation using fruit volatiles and insect sex pheromones with highly sensitive detection and signal processing. This was followed by the investigation of the feasibility of using the prototype cell-based biosensor system in a static mode for artificial insect olfaction applications, mimicking the cellular detection in the receptor/antenna apparatus of insects. Finally, as part of the development of a compact and low-power portable chemoreceiver system, the discrete sensor drive and interface circuitry was deployed in an analogue VLSI chip, thereby overcoming the associated measurement complexity and equipment cost, in addition to extending the reach and functionality of point of use technologie

Fluid compressional properties sensing at microscale using a longitudinal bulk acoustic wave transducer operated in a pulse-echo scheme

Altres ajuts: Acord transformatiu CRUE-CSICAcoustic devices have been widely used as smart chemical and biochemical sensors since they are sensitive to mechanical, chemical, optical or electrical perturbations on their surfaces; making them a reliable option for noninvasive detection of changes in physical properties of liquid samples for real-time applications. Here we present a longitudinal acoustic wave device for study of compressional properties of liquids in microfluidic systems, with the particularity of pulse-echo mode of operation. We have studied at a microscale the interaction between longitudinal acoustic waves and the compressional properties of liquid samples, interrogating the fluids with short pulses of ultrasound at GHz, finding a direct relationship between the magnitude of the bulk modulus or the specific acoustic impedance of liquids and the amplitude of the output voltage produced by acoustic echoes received by the aluminum nitride transducer. Analytical expressions and FEM simulations support the detection mechanism, while applications such as classification of liquids and detection of concentration change in solutions experimentally demonstrate the method. This contribution overcomes current restrictions of film acoustic resonators such as fragility of operation in liquid environments, high manufacturing cost or limitations regarding narrow microchannels; offering an alternative to applications that demand ultra-low consumption, miniaturization, versatility (it offers multi-frequency operation in 1 - 10 GHz range) and ease of readout (peak voltage)

Monolithic Integration Piezoelectric Resonators on CMOS for Radio-Frequency and Sensing Applications

Software cognitive radios and Internet of Things (IoT) are recent interest areas that need low loss and low power consumption hardware. More specifically, the area of software cognitive radios requires that hardware be frequency agile and highly selective. Meanwhile, IoT relies on multiple low power sensor networks. By combining Complementary Metal Oxide Semiconductors (CMOS) technology with piezoelectric Micro-Electro-Mechanical Systems (MEMS), we can fabricate Systems-on-Chip (SoC) that can be used as filters or references (oscillators) and highly selective sensors. In this work we developed a die-level compatible process for the monolithic integration of Bulk Acoustic Resonators (BAWs) on CMOS for low power, reduced area and high-quality passives for radio frequency applications. Using CMOS as a fabrication substrate some stringent requirements were added to maintain the dies and the technology’s integrity. A few of these limitations were the need for a low thermal budget fabrication process, die handling and electro-static discharge (ESD) protection. The devices were first fabricated on glass for modeling extraction that was later used for the design of the integrated circuits (IC). Three integrated circuits were designed as substrates for the integration using IBM’s 180nm and TSMC’s 65nm technology. A monolithic BAW oscillator with a resonance frequency of 1.8GHz was demonstrated with an FOM ~186dBc/Hz, comparable to other academia work. Using the developed process, a membrane BAW structure (FBAR) was integrated as well. Using a susceptor coating and zinc oxide’s (ZnO) high temperature coefficient of frequency (TCF) the device was studied as an alternative uncooled infrared sensor. Finally, a reprogrammable IC and an RF PCB were designed for volatile organic compound (VOC) testing using self-assembled monolayers (SAMs) as the absorber layer

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed