Wireless Passive Pressure Sensor Research Articles

A Wireless Passive Pressure Microsensor Fabricated in HTCC MEMS Technology for Harsh Environments

A wireless passive high-temperature pressure sensor without evacuation channel fabricated in high-temperature co-fired ceramics (HTCC) technology is proposed. The properties of the HTCC material ensure the sensor can be applied in harsh environments. The sensor without evacuation channel can be completely gastight. The wireless data is obtained with a reader antenna by mutual inductance coupling. Experimental systems are designed to obtain the frequency-pressure characteristic, frequency-temperature characteristic and coupling distance. Experimental results show that the sensor can be coupled with an antenna at 600 °C and max distance of 2.8 cm at room temperature. The senor sensitivity is about 860 Hz/bar and hysteresis error and repeatability error are quite low.

A SU-8-Based Microfabricated Implantable Inductively Coupled Passive RF Wireless Intraocular Pressure Sensor

With the growing demand in noncontact detection of human diseases, this paper presents an implantable passive wireless pressure sensor using an inductively coupled wireless sensing technique, particularly designed to monitor the intraocular pressure (IOP) of glaucoma patients. The microfabricated IOP sensor consists of a planar spiral gold coil inductor, a two-parallel-gold-plate (metal-insulator-metal) capacitor, and a SU-8 pressure-sensitive diaphragm. The IOP sensor is fully encapsulated inside biocompatible SU-8 stacking layers to isolate the IOP sensor from the biological tissue medium environment. By measuring the impedance phase dip frequency shift from the external coil, the IOP signal can be obtained through the implanted IOP sensor. The optimized size of the manually wound external coil was investigated. The readout distance is up to 6 mm from the implanted sensor. Characterization results show that the microfabricated IOP sensor has relatively high sensitivities-7035 ppm/mmHg in air and 3770 ppm/mmHg in saline medium-with pressure resolution lower than 1 mmHg, which is adequate for IOP monitoring application.

Working principle description of the wireless passive EM transduction pressure sensor

The development of a new passive wireless pressure sensor, based on an electromagnetic transduction approach, is reported. The sensing element is a flexible high resistivity silicon membrane located above a coplanar quarter-wavelength resonator. The comprehensive coverage of the physical bases is beyond the scope of this paper. For the remote extraction of the applied pressure value, the passive pressure sensor is connected to a broadband horn antenna via a coaxial delay line. When interrogated by a frequency modulated continuous wave radar, the level of the backscattered signal changes versus the pressure applied to the proof body. Through this interrogation principle, the sensor provides load impedance that is reflected back to the radar reader: the measured dynamic is about 0.8 dBm/bar. This completely passive and wireless pressure telemetry micro-sensor has been designed, fabricated and characterized, thereby eliminating the need for contact, signal processing circuits, and power supplies needed by conventional active sensors.

Passive single chip wireless microwave pressure sensor

A novel micromachined passive wireless pressure sensor is presented. The device consists of a tuned circuit operating at 10 GHz fabricated on to a SiO 2 membrane, supported on a silicon wafer. A pressure difference across the membrane causes it to deflect so that an antenna circuit detunes. The circuit is remotely interrogated to read off the sensor data wirelessly. The chip area is 5 mm × 4 mm and the membrane area is 2 mm 2 with a thickness of 4 μm. Two on-chip passive resonant circuits were investigated: a meandered dipole and a zigzag antenna. Both have a physical length of 4.25 mm. The sensors show a shift in their resonant frequency in response to changing pressure of 10.28–10.27 GHz for the meandered dipole, and 9.61–9.58 GHz for the zigzag antenna. The sensitivities of the meandered dipole and zigzag sensors are 12.5 kHz/mbar and 16 kHz/mbar respectively.

Design and modelling of a passive wireless pressure sensor

This investigation is concerned with the design and modelling of a passive wireless pressure sensor to detect blood pressure inside an abdominal aortic aneurysm sac after endovascular repair of the aneurysm. The sensor consists of a coil and a capacitor to form an inductor–capacitor ( LC) resonant circuit which oscillates electrically at its resonant frequency. This miniature sensor has a size of 6 mm × 6 mm × 1 mm and can be fabricated by microelectromechanical system (MEMS) technology. By activating the sensor with an electromagnetic field, aneurysm sac pressure information can be acquired. The properties and behaviour of this sensor based on computer simulation are also presented in this paper.

A Wireless, Passive Sensor for Monitoring the Pressure of an Abdominal Aortic Aneurysm Sac

Abdominal aortic aneurysms (AAA), which claim the lives of 15,000 Americans annually, occur when the aortic walls are weakened to the point of bulging or rupture. Besides aorta replacements, AAA is commonly treated with an endovascular aortic repair procedure that reinforces the aorta by inserting a stent via a leg artery. While this procedure is effective, failure of the stent may increase the pressure of the AAA sac and cause the aorta wall to rupture. Therefore, monitoring of the pressure in the AAA sac is critical for post surgery assessment. We present the design and fabrication of a wireless passive pressure sensor for measuring the pressure of an AAA sac after stent placement. The sensor is made of a hermetically sealed chamber with two opposite membranes. A magnetically soft film is attached on one of the membranes, and a permanent magnetic film is placed on the other. As the membranes deflect due to changes in sac pressure, the separation distance between the magnetic elements changes. This in turn varies the magnetic harmonic fields of the magnetically soft film, allowing remote pressure monitoring with the use of a magnetic coil. Compared to Endosure, a wireless passive sensor developed by CardioMems that operates by remotely measuring the resonant frequency change of a capacitive-inductive circuit, the proposed device is thinner and can be miniaturized to a long and thin strip. Its signal is also not reduced by the electrically dense body since it is interrogated through magnetic fields.

Design and Fabrication of Passive Wireless SAW Sensor for Pressure Measurement

This paper mainly presents the design and fabrication of a TDMA (time division multiple access) passive wireless pressure sensor using 2.45 GHz surface acoustic wave (SAW) delay lines. The SAW pressure sensor consists of two LiNbO3 substrates. The first layer is a pressure-detective thin substrate, on which an interdigital transducer (IDT) and reflectors are fabricated. The second layer is a support substrate, in which a reference pressure cavity is etched. These two substrates are directly bonded. The pressure measurement was successfully demonstrated in a pressure range of 20∼280 kPa with good repeatability. In addition, the influence of a tire on the wireless interrogation of the sensor was investigated. Automobile tires have little negative influence on wireless communication, at least if they do not rotate.