This paper presents a passive depolarizing and microfluidic sensor which was fully 3D printed from selective laser fusion additive manufacturing technology. The sensor includes a microfluidic channel filled with liquid metal (Galinstan) to measure the temperature. Experimental validation was performed by using a vision-guided radar system. The monolithic sensor demonstrated a maximum sensitivity of 6.6 dB/mm and a full-scale dynamic range of 15.1 dB in cross-polarization, showing significant improvement over previously reported version of the sensor based on multiple pieces. Additionally, interrogation of multiple sensors was achieved using color-coded labels for sensors identification.

This article presents an overview of 3-D-printed microwave and millimeter-wave components integrating gallium-based (Ga-based) liquid metal (LM). The LM is considered here as a fourth degree of freedom for the design of 3-D-printed antennas, filters, and wireless sensors. The 3-D printing combined with LM technology can be considered as a 4-D printing technology. It can benefit from the advantages offered by 3-D printing technologies (low cost and fast manufacturing) and LM at room temperature (flexibility and reconfigurability). To date, in microwave and millimeter-wave applications, 4-D printing technology is mainly used to achieve the metallization and/or reconfigurability and/or mechanical flexibility of high-frequency 3-D-printed components.

In this paper, we report the long-range and wireless interrogation of multiple chipless sensors from the isoline processing of three-dimensional polarimetric radar images. A Frequency-Modulated Continuous-Wave Radar operating at 24 GHz is used for the indoor interrogation of four sensors in the basement of a Laboratory. In such cluttered environment, the proposed radar image processing based on isolines computation allows the wireless measurement range of sensors up to 5.8m.

In this paper a new method based on the fusion of optical and radar data is proposed to detect and remotely interrogate mobile and passive sensors. The sensors are detected in real time by using an optical camera, while their remote reading is carried out on the fly using a Frequency-Modulated Continuous-Wave radar. The proof-of-concept is established from the interrogation of a microfluidic temperature sensor placed on a conveyer belt.

A polarimetric millimeter-wave radar imaging technique is proposed to remotely detect, localize, and wirelessly read a novel additively manufactured passive sensor composed of a microfluidic channel filled with liquid metal Galinstan. Very high variation of the radar-cross section of the sensor to small variations of the level of Galinstan in the channel is obtained. Indeed, at the radar-to-sensor distance of 2.4 m, the measured radar echo level of the sensor varies by 4.5 dB when the level of Galinstan changes by 1 mm. This sensitivity is higher than those previously reported in the literature for wireless and passive sensors of the same class. Moreover, the localization technique of the sensor is successfully achieved for only three false detections on 75 measurements in cluttered environments from radar-to-sensor distances up to 15 m.

This paper proposes two ways to improve pressure measurement in air-blast experimentations, mostly for close-in detonations defined by a small-scaled distance below 0.4 m.kg−1/3. Firstly, a new kind of custom-made pressure probe sensor is presented. The transducer is a piezoelectric commercial, but the tip material has been modified. The dynamic response of this prototype is established in terms of time and frequency responses, both in a laboratory environment, on a shock tube, and in free-field experiments. The experimental results show that the modified probe can meet the measurement requirements of high-frequency pressure signals. Secondly, this paper presents the initial results of a deconvolution method, using the pencil probe transfer function determination with a shock tube. We demonstrate the method on experimental results and draw conclusions and prospects.

In this study, we investigated the capacitive effect and the electromagnetic coupling on the measurement chain induced by impact experiments with a gas gun or powder gun. Reduced bandwidth and noise were noticed on experimental signals. Rogowski coil measurements were added on the cables to characterize the electromagnetic coupling. The perturbation currents on the cables were quantified depending on the configuration. The gauge, the transmission line and the conditioning system were modeled. The calculations reproduced the electrical wave arrival time, the transmission line transfer impedance and the conditioning system transfer impedance; and the bandwidth limitation has been displayed. A capacitive effect with the piezoresistive manganin gauge embedded into the sample was identified, depending on the experimental setup.

New broadband (>1 MHz) pressure sensors are regularly reported in the literature to measure the overpressure of blast waves. However, the frequency bandwidth needed to accurately measure such overpressure has not yet been clearly discussed. In this article, we present a methodology to determine the bandwidth required to estimate the overpressure magnitude at the front of a blast wave, in order to obtain a desired estimation accuracy. The bandwidth is derived here by using Kingery and Bulmash data.

— The packaging is an important step, allowing to transform the transducer chip into a sensor. This step is necessary to perform the sensor characterization in a real environment, while minimizing the impact of the influence parameters on the sensor response. This study concerns the impact of the packaging on the static response of a miniature pressure sensor dedicated to the monitoring of blast waves. The transducer is based on 5 µm - thick rectangular (55 µm x 135 µm) silicon membrane and piezoresistive gauges. Pressure sensitivity measurements are performed using stressed and non-stressed sensor’s holder configurations. Measurements results indicate that the pressure sensitivity is doubled when the sensor’s holder is stressed. Finite Element Method simulations using COMSOL Multiphysics software show here that this result originates from the deformation of the sensor’s holder, which leads to the deflection of the thin silicon membrane.

Blast waves generated by energetic materials involve very fast time variations in the pressure. One important issue for blast wave metrology is the accurate measurement (typical precision in the range of ±5% or better) of the static overpressure peak. For most near field configurations, this measurement requires ultra-fast sensors with response times lower than a few microseconds. In this paper, we design, model, fabricate and characterize a new ultra-fast sensor using piezo-resistive gauges at the center of a miniaturized and rectangular silicon membrane. When a pressure step of 10 bar is applied to the membrane, the signal delivered to the sensor output presents dampened oscillations, with a resonant frequency of 20.6 MHz and quality factor of 24,700 ns after the arrival of the shock wave. After removing undesirable drifts that appear after 700 ns, we may expect the sensor to have a response time (at ±5%) of 1.2 µs. Consequently, the proposed pressure sensor could be advantageously used for the accurate measurement of static overpressure peaks in blast wave experiments.

We investigate in this paper the wireless interrogation of chipless and passive mechanical sensors using a range-Doppler imaging algorithm. As an example, a Crookes radiometer illuminated by a light of controlled illuminance is interrogated by using a 24GHz FM-CW radar. A remote detection algorithm is proposed to estimate the reading range and Doppler harmonics embedded in the electromagnetic signal backscattered by the radiometer. From these harmonics the accurate estimation of illuminance is achieved for long reading ranges of at least 3.5m in a cluttered environment.

This paper reports the design, fabrication and measured performance of a passive microelectromechanical transducer for the wireless monitoring of high irradiation doses in nuclear environments. The sensing device is composed of a polymer material (high-density polyethylene) sealed inside a cavity. Subjected to ionizing radiation, this material releases various gases, which increases the pressure inside the cavity and deflects a dielectric membrane. From the measurement of the deflection, the variation of the applied pressure can be estimated, and, in turn, the dose may be determined. The microelectromechanical structure can also be used to study and validate the radiolysis properties of the polymer through its gas emission yield factor. Measurement of the dielectric membrane deflection is performed here to validate on the one hand the required airtightness of the cavity exposed to doses about 4 MGy and on the other hand, the functionality of the fabricated dosimeter for doses up to 80 kGy. The selection of appropriate materials for the microelectromechanical device is discussed, and the outgassing properties of the selected high-density polyethylene are analysed. Moreover, the technological fabrication process of the transducer is detailed.

During explosive detonation or air blast experiments, long cables are commonly used for transmitting signals delivered by pressure sensors to the safe place of the acquisition unit. While constant efforts are undertaken for enlarging the bandwidth of sensors in order to improve the measurement precision of the peak pressure, the limitations of the wired transmission of blast pressure signals delivered by these sensors are not addressed. We discuss here such limitations and propose a wireless new solution for the dynamic measurement of Friedlander-type signals delivered by ultra-wideband sensors (>10MHz ). Contrary to the wired solution, the distance between the sensor and the acquisition unit does not limit the measurement bandwidth of the wireless setup. Experimental results are reported for validation purposes and pave the way of the dynamic measurement of blast pressure variations occurring at the heart of the fireball generated during explosions.

This article describes the wireless and simultaneous interrogation and identification of multiple passive (zero-power) pressure sensors in an industrial environment with a reading range of at least 4 m. The 3-D beamscanning of the scene is performed from a 24-GHz frequency-modulated continuous-wave (FM-CW) radar and for diverse electric field polarizations. The identification is performed using a k-nearest neighbor classification. The benefit of using the cross-polarized electric fields combined with a radar imagery technique is enlightened from the analysis of the background clutter and the simultaneous remote interrogation of several passive pressure sensors at a distance up to 17.7 m. The measurement uncertainty on pressure obtained from the proposed long-range wireless technique is finally reported and discussed.

In this paper, we report the remote measurement of the pressure from the Radar interrogation of a novel microfluidic passive sensor. This sensor includes a microfluidic band-pass filter, whose transmission coefficient in the Ka-band depends on the applied pressure, and two cross-polarized Rx- and Tx-antennas connected to the terminals of the filter for enhancing the full-scale measurement range of the sensor's Radar echo level. The filter is 3D-printed via the Sintering Laser Melting technique. For a Radar-to-sensor distance of 3 meters, a high full-scale measurement range of 8dB on the echo level is reported with a measurement sensitivity of 0,03dB/mbar for applied pressure ranging from 350 mbar to 640 mbar.