Progress in the production and modification of PVDF membranes

Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.

/pdf/review-semiconductor-piezoresistance-for-microsystems-2i2jehwa4g.pdf

Review: Semiconductor Piezoresistance for Microsystems

This paper describes the design of a thermal comfort controller for indoor thermal environment regulation. In this controller, predicted mean vote (PMV) is adopted as the control objective and six variables are taken into consideration. Meanwhile, a kind of direct neural network (NN) control is designed, and a thermal space model for variable-air-volume (VAV) application is developed. Based on the computer simulation, it is seen that this thermal comfort controller can maintain the indoor comfort level within the desired range under both heating/cooling modes. Furthermore, by combining the energy saving strategy with the VAV application, it also shows the potential for energy saving in future

Thermal comfort control based on neural network for HVAC application

In building automation, comfort is an important aspect, and the real-time measurement of comfort is notoriously complicated. In this paper, we have developed a wireless, smart comfort sensing system. The important parameters in designing the prevalent measurement of comfort systems, such as portability, power consumption, reliability, and system cost, were considered. To achieve the target design goals, the communication module, sensor node, and sink node were developed based on the IEEE1451 standard. Electrochemical and semiconductor sensors were considered for the development of the sensor array, and the results of both technologies were compared. The sensor and sink nodes were implemented using the ATMega88 microcontroller. Microsoft Visual Studio 2013 preview was used to create the graphical user interface in C#. The sensors were calibrated after the signal processing circuit to ensure that the standard accuracy of the sensor was achieved. This paper presents detailed design solutions to problems that existed in the literature.

/pdf/an-energy-efficient-smart-comfort-sensing-system-based-on-3871lmiez9.pdf

An Energy-Efficient Smart Comfort Sensing System Based on the IEEE 1451 Standard for Green Buildings

This paper presents a novel single proof-mass tri-axis capacitive type complementary metal oxide semiconductor-microelectromechanical system accelerometer to reduce the footprint of the chip. A serpentine out-of-plane (Z-axis) spring is designed to reduce cross-axis sensitivity. The tri-axis accelerometer has been successfully implemented using the TSMC 2P4M process and in-house postprocessing. The die size of this accelerometer chip containing the MEMS structure and sensing circuits is 1.78 × 1.38 mm, a reduction of nearly 50% in chip size. Within the measurement range of ~0.8 6G, the tri-axis accelerometer sensitivities (nonlinearity) of each direction are 0.53 mV/G (2.64%) for the X-axis, 0.28 mV/G (3.15%) for the Y-axis, and 0.2 mV/G (3.36%) for the Z-axis, respectively. In addition, the cross-axis sensitivities of these three axes range from 1% to 8.3% for the same measurement range. The noise floors in each direction are 120 mG/rtHz for the X-axis, 271 mG/rtHz for the Y-axis, and 357 mG/rtHz for the Z-axis.

/pdf/implementation-of-a-monolithic-single-proof-mass-tri-axis-1whzmrhfrm.pdf

Implementation of a Monolithic Single Proof-Mass Tri-Axis Accelerometer Using CMOS-MEMS Technique

A three-axis piezoresistive acceleroraeter has been fabricated by bulk-micromachining and SDB (silicon direct bonding) technologies using a polysilicon layer. The results of FEM (finite-element method) simulation for each acceleration direction have been utilized to detect the three-dimensional acceleration and eliminate cross-axis sensitivities. The relative changes of resistance as a function of temperature in LPCVD polysilicon layers with boron implantation dose are described. TCO (temperature coefficient of offset) shifts for the X-, Y- and Z-axis Wheatstone bridge outputs are only about 0 to 0.07, 0.028 to − 0.016 and 0.007 to − 0.004 %F.S. in the 25–160 °C range, respectively. The resonance frequencies of the fabricated accelerometers are 6.560, 8.930 and 18.350 kHz at the first, second and third mode, respectively. The sensitivities of the fabricated sensor for X-, Y- and Z-axis acceleration are about 0.276, 0.226 and 0.793 mV (V g)−1 at room temperature. The cross-axis sensitivity for X-, Y- and Z-axis acceleration is about 0.01 mV (V g)−1, which represents the elimination of cross-axis sensitivities, as designed.

A bulk-micromachined three-axis accelerometer using silicon direct bonding technology and polysilicon layer

This research is about an integrated comfort sensing system on indoor climate using humidity, temperature and air flow sensors with integrated driving and amplifying circuit. The comfort sensing appears to be highly sensitive to temperature and air flow. We have designed and fabricated a one-bodied humidity/temperature sensor and a flow sensor. In order to drive sensors and amplify signals, the ASIC chip has been designed and integrated by CMOS technology. Because the first ASIC chip was not good for driving and amplifying signals, we designed and fabricated a different OP-AMP cell of the circuit. The microcontroller calculates a predicted mean vote (PMV) and comfort sensing vote (CSV) with sensing signals and displays a PMV on liquid crystal display (LCD) for human comfort on indoor climate. Our work has demonstrated that an integrated comfort sensing system can provide an effective means of measuring the indoor comfort sensing index of a human being. Experimental results with simulated environment clearly suggest that our sensing system can be used in many applications such as air conditioning system, feedback controlling in automobiles, homes, hospitals, etc.

Integrated comfort sensing system on indoor climate

A three axis piezoresistive accelerometer was fabricated from a polysilicon layer using SDB (silicon direct bonding) technology and LPCVD. The variations of stress according to each direction were utilized to detect the three dimensional acceleration and eliminate cross-axis sensitivities. TCO (temperature coefficient of offset) shifts for X, Y and Z-axis Wheatstone bridge outputs were only about 0/spl sim/0.07[%F.S.], 0.028/spl sim/-0.016[%F.S.] and 0.007/spl sim/-0.004[%F.S.] in the 25/spl deg/C/spl sim/160/spl deg/C range, respectively. The sensitivities of the fabricated sensor for X, Y and Z-axis acceleration were about 0.06[mV/V/spl middot/g], 0.06[mV/V/spl middot/g] and 0.13[mV/V/spl middot/g] at room temperature. The cross-axis sensitivity for X, Y and Z-axis acceleration was about 0.0093[mV/V/spl middot/g], which corresponds to the elimination of cross-axis sensitivities as designed.

Three axis piezoresistive accelerometer using polysilicon layer

This study describes a non-invasive optical sensor and sensor system used to measure the blood oxygen saturation of an artificial heart, in vitro . The reflection type optical sensor consists of an LED for the light source and a PIN photodiode for the light detector in a flat pack. The emission wavelengths of the LED are 665 and 805 nm. The blood oxygen saturation was measured using the reflectance ratio of 665 to 805 nm. The sensor system for measurement of the oxygen saturation has been breadboarded. Changes in the blood oxygen saturation were detected by the developed sensor system in real time. The experimental set-up was designed to be identical in effects and circumstances to a living body. The non-invasive measurement of oxygen saturation in vitro was carried out. Using a constant volume (30 cc) of blood and various volumes (0, 10, 20, 30 cc) of a physical saline solution, the hematocrit level of the blood was determined. When the change in oxygen saturation is compared at each wavelength, the variation at 665 nm is four times more than at 805 nm. At the 805 nm wavelength there was only a small change over the 100-60% range of oxygen saturation. The reflectance ratio decreased with reduction of the hematocrit level. As the oxygen saturation was varied from 100 to 60%, the reflectance ratio R 805/ R 665 over the whole hematocrit range changed linearly.

An optical sensor for the non-invasive measurement of the blood oxygen saturation of an artificial heart according to the variation of hematocrit

To form spacers with a high aspect ratio on an anode plate for field emission displays (FEDs), glass to glass anodic bonding was used. A rib-type soda lime glass, width 100??m?height?1000??m?length 75?mm, was used as a spacer and bonded on a 3.54?in mono green color anode plate patterned with Al/Cr film as an interlayer by anodic bonding. To bond the spacers on the anode plate vertically, two types of spacer holders were fabricated and tried with photoetchable glass and an n-type (110) Si wafer. The spacer process was used to fabricate an evacuated FED panel.

http://iopscience.iop.org/article/10.1088/0960-1317/10/3/316/pdf

Se-Kwang Park

Papers

A bulk-micromachined three-axis accelerometer using silicon direct bonding technology and polysilicon layer

Integrated comfort sensing system on indoor climate

Three axis piezoresistive accelerometer using polysilicon layer

An optical sensor for the non-invasive measurement of the blood oxygen saturation of an artificial heart according to the variation of hematocrit

Process of spacer with high aspect ratio for field emission display