Wireless Sensor Array Research Articles

100 Temperature-field reconstruction in 3D for minimally invasive cryosurgery based on medical imaging and/or wireless implantable temperature sensors

The objective of the current study is to develop a 3D temperature-field reconstruction method for minimally invasive cryosurgery—the destruction of undesired tissues by freezing. The new method is based on input data from medical imaging and/or an array of wireless implantable temperature sensors. A major difficulty in cryosurgery is the creation of a frozen region to conform to the planned 3D target region, while preserving the surrounding healthy tissues. In minimally invasive prostate cryosurgery for example, a dozen or more cryoprobes are inserted into the gland and operated simultaneously with a urethral warmer, in order to create the desired temperature field. Currently, the procedure is monitored with medical imaging (frequently ultrasound), sometimes with additional input from one or a couple of wired temperature sensors at the tip of a hypodermic needle. The development of ultra-miniature, wireless implantable sensors represents a parallel effort by the current research team. Temperature-field reconstruction in the current study is obtained by solving the classical bioheat equation, with input including temperature data from implantable sensors, and freezing-front location from medical imaging. A practical and computationally inexpensive approach is to assume a quasi-steady process in the frozen domain, based on the observation that the heat transfer during cryosurgery is characterized by a low Stefan number (i.e., the ratio of sensible to latent heat). It follows that the temperature distribution in the frozen region can be approximated as a steady solution at any instant, where the transient nature of the system comes about through boundary conditions. Since the thermophysical properties of the tissue are highly temperature dependent, a predictor-corrector iterative approach is adopted. A full transient bioheat transfer simulation of the procedure is generated by a commercially available code to serve as a benchmark, in order to evaluate the performance of the proposed algorithm. Results of this study suggest that: (a) the uncertainty in simulations based on the proposed algorithm is comparable with uncertainty in ultrasound imaging (1–2 mm) even in cases where only partial freezing front data is available (harvesting such data from medical imaging represents an unmet need); (b) the outcome of the proposed algorithm is equally adequate when temperature data from implantable temperature sensor is the only available input information; and, (c) a hybrid method incorporating data from imaging and temperature sensors seems to be a very promising approach for real-time feedback during cryosurgery. While the significance of the proposed method is in enabling cryosurgeons to visualize the developing thermal field in real time, the broader significance of the current study is in its applicability to other energy modalities in medicine with very little modifications. Source of funding: Award Number R21EB009370 from the National Institute of Biomedical Imaging and Bioengineering (NIBIB). Conflict of interest: None declared. cthaokar@andrew.cmu.edu

Wireless Intelligence Sensor Array for Air Parameter Monitoring

This paper proposes a multiple target air parameters monitoring scheme with the help of the wireless intelligence sensor array which is built up with multiple sensors. In the paper, the design of the wireless intelligence array sensor is considered, the method to configure the wireless intelligence sensor network is introduced, and the information combination arithmetic of sensor network is provided. Then, a kind of minitype wireless multiple target air parameters monitoring system is built up. Experiment result clearly indicates that the system can accomplish the mission of monitoring multiple targets at the same time and the efficiency and reliability, make the air parameter monitoring arrives at a higher level. So the system proposed should be widely used in the domain of air parameter and toxic and harmful gas leakage monitoring.

Smart wireless sensing and assessment for civil infrastructure

Recently, there has been increasing need for adopting smart sensing technologies to structural health monitoring (SHM) applications for civil infrastructure. In this paper, the state of the art in smart wireless sensing and assessment techniques for civil structures are reviewed focusing on full-scale applications. Three types of smart wireless sensing technologies are discussed: wireless acceleration sensor-based SHM, wireless impedance-based SHM and an optics-based non-contact actuation and sensing technique. At first, vibration-based SHM using a dense array of wireless acceleration sensors is implemented to a cable-stayed bridge. The modal identification of the bridge and cable tension estimation are carried out using the ambient acceleration data. Measured data during a typhoon is also discussed. Secondly, impedance-based SHM using piezoelectric active sensors is presented focusing on hardware and software issues. A wireless impedance sensor node is presented for local SHM and neural network-based smart assessment algorithm is proposed to detect multi-type damages. Finally, a wireless power and data transmission method using laser and optoelectronic technologies is presented for non-contact measurement of guided waves and impedance, and subsequent damage detection. This method is embodied in a small printed circuit board, and the performance is validated on a lab-scale steel truss member.

In vivo and in situ evaluation of a wireless magnetoelastic sensor array for plastic biliary stent monitoring

This paper presents the in vivo and in situ evaluation of a system that wirelessly monitors the accumulation of biliary sludge in a plastic biliary stent. The sensing element, located within the stent, is a passive array of magnetoelastic resonators that is queried by a wireless electromagnetic signal. The in vivo and in situ testing uses commercially-available plastic biliary stents, each enhanced with an array of ribbon sensors (formed from Metglas™ 2826 MB). The sensor array is approximately 70 mm long and contains individual resonators that are 1 mm in width and have lengths of 10 mm, 14 mm, and 20 mm. The array is anchored into the 2.8 mm inner-diameter stent using a thermal staking technique. For the in situ testing, an instrumented stent is placed in various locations within the abdominal cavity of a female domestic swine carcass to evaluate the wireless range of the system; these results show that a wireless signal can be obtained from a range of at least 7.5 cm from a sensor array covered in bile. The in vivo testing includes the endoscopic implantation of an instrumented stent into the bile duct of a swine. After implantation, the swine was housed for a period of 4 weeks, during which the animal showed no ill effects and followed the expected growth curve from 29 kg to 42 kg. At the conclusion of the in vivo test, the animal was euthanized, and the instrumented stent explanted and examined. The results presented in this paper indicate that the monitoring system does not adversely affect the health of the animal and can feasibly provide sufficient wireless range after implantation.

A packaging solution utilizing adhesive-filled TSVs and flip–chip methods

A compact packaging solution for microelectromechanical systems (MEMS) devices is presented. The 3D-integrated packaging solution was designed for the instrumentation of a spinal screw with a wireless sensor array, but may be adapted for a variety of applications. To achieve the compact package size, an unobtrusive through-silicon via (TSV) design was added to the microfabrication process flow for the MEMS sensor. These TSVs allowed vertical integration of the MEMS devices onto flexible printed circuit boards (FPCBs) using a flip–chip system. Ohmic connections with resistance values below 1 Ω have been achieved for 100 µm TSVs in 300 and 500 µm substrates. This paper describes the design and microfabrication process flow for the TSVs, and provides details on the flip–chip techniques used to electrically and structurally connect the MEMS devices to the FPCBs.

Systems And Methods For Interference Suppression With Directional Sensing Patterns

System (10) is disclosed including an acoustic sensor array (20) coupled to processing subsystem (30). System (10) processes inputs from array (20) to extract a desired acoustic signal through the suppression of interfering signals. The extraction/suppression is performed by modifying the array (20) inputs in the frequency domain with weights selected to minimize variance of the resulting output signal while maintaining unity gain of signals received in the direction of the desired acoustic signal. System (10) may be utilized in hearing , cochlear implants, speech recognition, voice input devices, surveillance devices, hands-free telephony devices, remote telepresence or teleconferencing, wireless acoustic sensor arrays, and other applications.

Design of a Robust, High-rate Wireless Sensor Network for Static and Dynamic Structural Monitoring

Over recent years, there has been much interest in the use of low-cost wireless transceivers for communication of sensor data to alleviate the expense of widely distributed cable-based sensors in structural monitoring systems. However, while the number of unique wireless sensor platforms has continued to expand rapidly, the lack of success in replicating the number of deployed sensors and sampling rates utilized in previous cable-based systems has led to disillusionment over their use for this application. This article presents a wireless sensing system designed for concurrent measurement of both static and dynamic structural response through strain transducers, accelerometers, and temperature sensors. The network protocol developed supports real-time, high-rate data acquisition from large wireless sensor arrays with essentially no data loss. The current network software enables high-rate acquisition of up to 40 channels across 20 wireless units on a single peer-to-peer network with system expansion enabled through additional networks operating simultaneously on adjacent communication channels. Elements of the system design have been specifically tailored towards addressing condition assessment of highway bridges through strain-based load ratings as well as vibration-based dynamic analysis. However, the flexible system architecture enables the system to serve essentially as an off-the-shelf solution for a wide array of wireless sensing tasks. The wireless sensing units and network performance have been validated through laboratory tests as well as dense large-scale field deployments on an in-service highway bridge.

Automated Modal Parameter Estimation by Parallel Processing within Wireless Monitoring Systems

With recent advances in low-cost wireless sensing and data acquisition technology, it has become feasible to instrument a large structure with a dense array of wireless sensors. Furthermore, analog-to-digital conversion and data processing capabilities of current wireless sensor prototypes offer the ability to efficiently distribute data processing tasks across a large network of wireless sensing nodes. For decades, the structural engineering community has been adapting input-output modal identification techniques for use in large-scale civil structures. However, unlike in mechanical or aerospace engineering, it is often difficult to excite a large civil structure in a controlled manner. Thus, additional emphasis has been placed on developing a number of output-only modal identification methods for use in structural engineering applications. In this paper, three of these output-only methods peak picking, random decrement, and frequency domain decomposition are modified for implementation in a distributed array of processors embedded within a network of wireless sensor prototypes. The software architecture proposed emphasizes parallel data processing and minimal communication so as to ensure scalability and power efficiency. Using the balcony of a historic theater in metropolitan Detroit as a testbed, this network of wireless sensors is allowed to collect and process acceleration response data during a set of vibration tests. The embedded algorithms proposed in this study are used to autonomously determine the balcony's modal properties with network-derived results found to be comparable to those derived from traditional offline techniques.

A real-time wireless smart sensor array for scheduling irrigation

A prototype real-time, smart sensor array for measuring soil moisture and soil temperature that uses off-the-shelf components was developed and evaluated for scheduling irrigation in cotton. The array consists of a centrally located receiver connected to a laptop computer and multiple sensor nodes installed in the field. The sensor nodes consist of sensors (up to three Watermark ® soil moisture sensors and up to four thermocouples), a specially designed circuit board, and a Radio Frequency IDentification (RFID) tag which transmits data to the receiver. The smart sensor array described here offers real potential for reliably monitoring spatially variable soil water status in crop fields. The relatively low cost of the system (∼USD 2400 for a 20-sensor node system) allows for installation of a dense population of soil moisture sensors that can adequately represent the inherent soil variability present in fields. This paper describes the smart sensor array and testing in a cotton crop. Integration of the sensors with precision irrigation technologies will provide a closed loop irrigation system where inputs from the smart sensor array will determine timing and amounts for real-time site-specific irrigation applications.

Wireless resonant sensor array for high-throughput screening of materials

Screening of materials arrays for their viscoelastic, gas-sorbing, and dielectric properties is important in a wide variety of combinatorial materials science applications. Impedance analysis is an attractive approach to analyze these materials properties and to generate the required new knowledge. Often, these measurements are performed by applying a material onto a suitable sensor and monitoring the changes in materials properties. However, when such a sensor is positioned into a test cell, a direct-wired connection to the analyzer becomes complicated. These complications further increase dramatically when a whole array of sensors is being tested in the test cell. To eliminate these complications, we developed a wireless proximity resonant sensor array system. In the developed system, tested materials are applied onto an array of thickness-shear mode (TSM) resonators operating at 10 MHz and arranged for performance testing in a test chamber. Each TSM resonator is coupled to a receiver coil (antenna). An array of these coils is read with a single scanning transmitter coil or an array of transmitter coils. This high-throughput screening approach of sensing materials permits their evaluation in complex environments where additional wiring is not desirable or adds a prohibitively complex design. We demonstrated the applicability of the wireless sensor materials screening approach for the rapid evaluation of the effects of conditioning of polymeric sensing films at different temperatures on the vapor-response patterns to several vapors of industrial, health, law enforcement, and security interest (ethanol, acetonitrile, and water vapors).

Design and fabrication of passive wireless sensor array system using composite coding resonant SAW transducer

This paper presents a novel composite SAW (surface acoustic wave) passive wireless sensor system involving a resonator and a delay line. While the interrogational signal is a sinusoidal burst, the response is a delayed and damped oscillation. The frequency and the delay time of response are related to the measurand and the coding of the sensor element, respectively. The composite sensor consists of a SAW resonator and a delay line. It combines the advantages of these two devices and can be used as elements of multiple sensors for longer distance passive wireless measurements. As the wireless sensing response is weak and transient, in order to get the response with the maximum signal-to-noise ratio, the interrogational frequency is designed to be adjustable according to the result of frequency estimation. As a result, an optimal sensing result is achieved. In the transceiver set-up, the software DDS (direct digital synthesis) source with a rather high resolution is implemented to track the passive wireless sensor. An isolated switch is set in transmitter to depress the correlation leakage noise after switching off the wireless RF (radio frequency) interrogation signal. In this paper, the characteristics of the response, the working procedure of the signal processing, sensor temperature test results and the system error analyses are elaborated. A prototype instrument is built. Experimental results show the effectiveness of the instrumentation and the advantages of the composite sensor system.

Wireless sensor array system for combinatorial screening of sensor materials

AbstractScreening of materials arrays for their viscoelastic, gas-sorbing, and electrical properties is important for a variety of practical applications ranging from sensor to protective coatings. Complex impedance analysis of the materials arrays is an attractive approach to analyze these materials properties. We developed a wireless proximity sensor array system for combinatorial screening of these types of materials and demonstrated its applicability for sensor materials. In the developed system, sensor materials are applied onto an array of resonators and arranged for performance testing in a test chamber. Each resonator is coupled to a receiver antenna. An array of these antennas is read with a single scanning transmitter antenna or an array of transmitter antennas. Such high-throughput screening approach of sensor materials permits their evaluation in complex environments where additional wiring is not desirable or adds a prohibitively complex design.