Fully integrated three dimensional sound intensity sensor

For the first time, a complete 3-dimensional sound intensity sensor – consisting of 4 particle velocity sensors and a pressure microphone – has been integrated on a single chip, providing the possibility to do nearly point measurements of acoustic particle velocity, sound pressure, and therefore sound intensity. Principally the sensor consists of two distinct designs; a pressure sensor and particle velocity sensors. In this paper the design of the sensor, fabrication and measurement results are discussed and compared with theoretical results

A Micromechanical Parylene Spiral-Tube Sensor and Its Applications of Unpowered Environmental Pressure/Temperature Sensing

A multi-function micromechanical pressure/temperature sensor incorporating a microfabricated parylene spiral tube is presented. Its visible responses in expression of in situ rotational tube deformation enable unpowered sensing directly from optical device observation without electrical or any powered signal transduction. Sensor characterizations show promising pressure (14.46°/kPa sensitivity, 0.11 kPa resolution) and temperature (6.28°/°C sensitivity, 0.24 °C resolution) responses. Depending on different application requests, this sensor can be individually utilized to measure pressure/temperature of systems having one property varying while the other stabilized, such as intraocular or other in vivo pressure sensing of certain apparatus inside human bodies or other biological targets. A straightforward sensor-pair configuration has also been implemented to retrieve the decoupled pressure and temperature readouts, hence ultimately realizes a convenient environmental pressure and temperature sensing in various systems

Gas leak detector is simple and inexpensive

Pressure sensor monitors small gas leaks in piping and pressure vessels. A combination of a paper ribbon and adhesive plastic tape is used to cover the area to be monitored and the pressure sensor is placed over a hole in the tape and paper

Exploitation of a pH-sensitive hydrogel for CO2 detection

In this paper is described how hydrogel is exploited as sensor material for the \ud detection of carbon dioxide (CO2). A pH-sensitive hydrogel disc, which swells and deswells in response to pH changes, was clamped between a pressure sensor membrane and a porous metal screen together with a bicarbonate solution. Bicarbonate reacts with CO2 resulting in a pH change. The enclosed hydrogel will generate pressure as a response to the pH change. This pressure is a measure for the partial pressure of CO2. The main advantage of this sensor principle is the lack of a reference electrode as required for potentiometric sensors

A new tonometer based on the application of micro-mechanical sensors

An instrument for the measurement of intraocular pressure (IOP) is presented. It consists of a micromachined silicon sensor, which measures the diameter of a flattened part of the eye globe and simultaneously determines the smallest distance between the center of the sensor and the contour of this applanation. In the center of this applanation sensor a micro mechanical plunger is realized, which transfers the applied pressure to a separate force sensor. Preliminary results show that this sensor may improve the accuracy of Mackay-Marg-based electronic tonometer

Microfabricated Implantable Parylene-Based Wireless Passive Intraocular Pressure Sensors

This paper presents an implantable parylene-based wireless pressure sensor for biomedical pressure sensing applications specifically designed for continuous intraocular pressure (IOP) monitoring in glaucoma patients. It has an electrical LC tank resonant circuit formed by an integrated capacitor and an inductor coil to facilitate passive wireless sensing using an external interrogating coil connected to a readout unit. Two surface-micromachined sensor designs incorporating variable capacitor and variable capacitor/inductor resonant circuits have been implemented to realize the pressure-sensitive components. The sensor is monolithically microfabricated by exploiting parylene as a biocompatible structural material in a suitable form factor for minimally invasive intraocular implantation. Pressure responses of the microsensor have been characterized to demonstrate its high pressure sensitivity (> 7000 ppm/mmHg) in both sensor designs, which confirms the feasibility of pressure sensing with smaller than 1 mmHg of resolution for practical biomedical applications. A six-month animal study verifies the in vivo bioefficacy and biostability of the implant in the intraocular environment with no surgical or postoperative complications. Preliminary ex vivo experimental results verify the IOP sensing feasibility of such device. This sensor will ultimately be implanted at the pars plana or on the iris of the eye to fulfill continuous, convenient, direct, and faithful IOP monitoring

Nanowire Zinc Oxide MOSFET Pressure Sensor

Fabrication and characterization of a new kind of pressure sensor using self-assembly Zinc Oxide (ZnO) nanowires on top of the gate of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is presented. Self-assembly ZnO nanowires were fabricated with a diameter of 80 nm and 800 nm height (80:8 aspect ratio) on top of the gate of the MOSFET. The sensor showed a 110% response in the drain current due to pressure, even with the expected piezoresistive response of the silicon device removed from the measurement. The pressure sensor was fabricated through low temperature bottom up ultrahigh aspect ratio ZnO nanowire growth using anodic alumina oxide (AAO) templates. The pressure sensor has two main components: MOSFET and ZnO nanowires. Silicon Dioxide growth, photolithography, dopant diffusion, and aluminum metallization were used to fabricate a basic MOSFET. In the other hand, a combination of aluminum anodization, alumina barrier layer removal, ZnO atomic layer deposition (ALD), and wet etching for nanowire release were optimized to fabricate the sensor on a silicon wafer. The ZnO nanowire fabrication sequence presented is at low temperature making it compatible with CMOS technology

Wide-range dynamic pressure sensor

Transducer measures pressure by sensing the damping of a vibrating diaphragm immersed in the atmosphere to be measured. Improved sensor can be included in rugged, lightweight package for use aboard aircraft, meteorological vehicles, and space probes

Implantable Unpowered Parylene MEMS Intraocular Pressure Sensor

This paper presents the first implantable, unpowered, parylene-based micro-electro-mechanical-systems (MEMS) pressure sensor for intraocular pressure (IOP) sensing. From in situ mechanical deformation of the compliant structures, this sensor registers pressure variations without power consumption/transduction. Micromachined high-aspect-ratio thin-walled tubes in different geometric layouts are exploited to obtain a high-sensitivity pressure response. An integrated packaging method has been successfully developed to realize suture-less implantation of the device. In vitro testing results have demonstrated that the IOP sensor can achieve 0.67 degree/mmHg angular sensitivity with a spiral-tube design, 3.43 µm/mmHg lateral sensitivity with a long-armed-tube design, and 0.38 µm/mmHg longitudinal sensitivity with a serpentine-tube design. This IOP sensor is designed to be implanted in the anterior chamber of the eye and anchored directly on the iris so that, under incident visible light, the pressure response of the implant can be directly observed from outside the eye, which enables faithful and unpowered IOP monitoring in glaucoma patient