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We propose a pure photosynthates extraction sensor device integrated with highly precise phloem/xylem position identification to quantitatively monitor the components of internal higher plants, which is a key indicator for controlling stable crop production. The essential functions of the device are high-precisely identifying phloem/xylem positions based on electrical conductivity and extracting pure phloem sap. We fabricated the proposed device with microelectromechanical systems technology and evaluated its effectiveness. It is confirmed that the performance of our fabricated electrical conductivity sensor is almost equal to that of a commercially available meter. (The error of these characteristic lines is less than 5%.) Experiments with cucumber stems confirmed that the device can precisely measure the electrical conductivity of phloem/xylem sap in the appropriate range of internal plants or soil (0.0-1.0 mS/cm), identifying their positions stably over a long period. Extraction experiments demonstrated that phloem sap from the internal plant flows readily into the extraction flow channel and a reservoir. Therefore, we clearly demonstrated the feasibility of a novel sensor device that can conveniently identify the phloem positions and extract pure photosynthates samples in agricultural situations.

This paper presents the radio frequency (RF) transmitter using pulsewidth modulation (PWM) method. The proposed transmitter can perform with lower power consumption compared to other RF transmitters using a conventional ring oscillator because the proposed voltage-controlled oscillator (VCO) is operated by ON-/OFF-time of the PWM signal. Moreover, the proposed VCO with a metal-oxide semiconductor switch can reduce the power consumption significantly due to the reduction of idle current loss. The power dissipation of the transmitter is measured as 0.75 mW at a carrier of 315 MHz. The transmission of the modulated signal is performed by the on-chip antenna with bond-wire inductor. The on-chip antenna has gain of -34.33 dBi. The radiated power is measured as -32.3 dBm at a distance of 10 cm between the receiver and the transmitter.

In this paper, a versatile integration technology for thick-film silicon-on-insulator microelectromechanical systems (SOI-MEMS) devices with CMOS electronics using novel microbridge interconnections is reported. The microbridge interconnection proposed in this paper solves the problem regarding the electrical isolation and interconnection between CMOS and SOI-MEMS devices. The integration of SOI-MEMS requires only three additional photolithography steps for the CMOS wafers fabricated by a standard process. On the basis of the developed technology, SOI-MEMS devices integrated with CMOS circuits were fabricated using 20-μm-thick SOI wafers. No significant damage was observed in the measured characteristics of the fabricated CMOS after the integration of MEMS devices. In addition, the electrical isolation of SOI-MEMS from the CMOS substrate was successfully realized and confirmed in the experiment, keeping electrical connectivity between CMOS circuit terminals. The measured isolation resistance between MEMS and the CMOS substrate was more than 1012 Ω, and a proof voltage above 60 Vdc was observed. These values guarantee a small leakage current and a sufficient voltage swing for driving electrostatic microactuators. On the other hand, the resistance of the interconnection over a microbridge structure was below 1 Ω, which is sufficiently low for integrating low-noise microsensors. This integration technology can be used in realizing monolithically integrated SOI-MEMS sensor and actuator devices with high-aspect-ratio structures using the most cost-effective and versatile CMOS fabrication technologies.

This paper reports about a novel wafer-level integration technique of discrete surface mount devices (SMDs). It enables wafer-level mounting of plural kinds of SMDs on a silicon (Si)-wafer using vibration and gravity force. Deep holes with 400-m depth are formed on the surface of a Si-wafer by deep reactive ion etching process after general integrated circuit process for positioning of SMDs. A non-conductive adhesive (CYTOP) are coated on the deep holes and it is used to fix the aligned SMDs. SMDs are distributed on a Si-wafer mounted on vibration generator, and then a vibration is applied. The SMDs migrate due to the reduced friction between the wafer surface, and they drop into the holes on the silicon wafer. The size of the holes has an appropriate clearance to the size of SMD. In order to align two or more kinds of SMDs, sizes of the deep holes on a Si-wafer are adjusted to the size of each SMD. SMDs with the largest size are dropped into the holes first, and then the secondary large SMDs are dropped into the holes with the corresponding size. SMDs are finally connected electrically by wire bonding at the final step. In the experiment, two different sizes of SMD were successfully mounted into all the holes on a Si-wafer automatically. This technology will be a wafer-level process technology which is very promising to integrate two or more kinds of discrete elements.

In this paper, a novel concept of silicon-microelectromechanical system tactile image sensor aimed at fingertip tactile applications and evaluation results of a prototype device are presented. Array of strain-sensitive sensor pixels is integrated on a pneumatically swollen silicon diaphragm with signal processing circuits in monolithic configuration. Elastic surface of the tactile image sensor is realized using repulsive force of the air pressure applied to diaphragm backside. Contact force distribution of an object is detected from the stress distribution change on the diaphragm using piezoresistor array. Force range and force sensitivity can be controlled by the pressure even after device packaging step. In this principle, fine pitch of pixels and a large-scale sensing array can be easily realized using the abilities of silicon CMOS technology. In addition, the movable stroke of sensor surface can be made much longer than the individually formed micromechanical pixels. A prototype device, of the new concept, with 3040 /spl times/ 3040 /spl mu/m/sup 2/ sensing diaphragm was fabricated with integrated 6 /spl times/ 6 array of 420-/spl mu/m pitch pixels. Increased movable stroke of the swollen diaphragm from the original surface is around 30 /spl mu/m at 23-kPa pressure at the top. Realized spatial resolution of the prototype device is approximately 400 /spl mu/m, which is determined by the relationship between the pixel pitch and mechanical crosstalk among the pixels. Positions of touch and their contact force amplitudes were detected as a two-dimensional distribution of the output voltage from the pixel array in a multipoint contact test. The maximum input-force range can be controlled from 21 to 176 mN by changing the backside pressure from 5 to 64 kPa. Through the evaluation of the fabricated device, major advantages of this tactile image sensor have been demonstrated successfully.

A new method is presented of on-chip optical spectroscopy, functioning without the need for a bandpass filter or grating. The principle of optical spectroscopy is based on the difference of optical absorption coefficients with wavelength. The optical intensity is calculated from the different penetration depths in Si. The key to the new spectrometer is the use of a photogate active pixel providing the selective control of photo-generated charge using the gate voltage. To demonstrate this spectrometer, a novel filterless fluorescence detection sensor has been fabricated in our laboratory, using standard 5-/spl mu/m CMOS silicon integrated circuit technology. The SYBR-Green label fluoresces at 520 nm when exited by 470-nm radiation. In a simulation experiment using two LEDs, the fluorescent intensity detected was 1/300 of the excitation light intensity (intensity of fluorescence was 1 /spl mu/W/cm/sup 2/, while the excitation illumination was 300 /spl mu/W/cm/sup 2/). In an experiment using actual DNA solution containing SYBR-Green, it was confirmed that the fluorescence detection sensor successfully detected the fluorescent label without the need for a filter.

In this paper, a new concept and potential demonstration of functional microfluidic integrated circuits using MEMS technology are presented. The fluidic integrated circuits were constructed utilizing analogous relationship between MOSFET and pneumatic microvalve with a diaphragm structure. The signal transmitted through the circuit is the fluidic signal, that is, the pressure or the flow-rate of the fluid. The pneumatic microvalve in this study is expressed by small-signal equivalent model similar to that of a MOSFET. Small signal behavior of microfluidic integrated circuits can be expected using the model, if the parameters in the model are extracted properly from fabricated microvalves. As an example of a fluidic circuit, pressure inverting amplifiers including integrated two microvalves were fabricated and evaluated. As a result, they showed sharp pressure transfer curves similar to MOS inverter circuits. A maximum pressure gain of 32.0 dB was obtained, and it can be used for pressure amplification in analog applications. In addition, they can be used as pressure inverter logic circuits for digital applications. Although the theory and design environment of the new microvalve circuit technology have not been established yet, multifunctional fluidic analog and digital circuits can be realized for special application fields different from electronic integrated circuits.

A pneumatically actuated silicon microvalve applicable to integrated microfluidic systems is presented. All the ports of this microvalve are in-channel, and connectable to any surface fluid channels in microfluidic systems. This microvalve controls fluid flow by means of the controlled gap between glass and silicon diaphragm actuated by a control pressure. In addition, the diaphragm is also deformed by the outlet pressure of the microvalve. Due to the feature, this microvalve shows saturation of flow rate like MOSFETs operated at saturation region. The fabricated microvalve device was evaluated focusing on analogous relationship between MOSFET and the microvalve. Fluids such as air and DI-water were well controlled by the control pressure. Fluid starts to flow in the microvalve when the control pressure exceeds its "threshold pressure." Hysteresis due to sticking of diaphragm was not observed in the characteristics. Air flow rate of the microvalve was gradually saturated with the increasing of the outlet pressure as expected. Through the evaluation, analogous relationship between this microvalve and MOSFET has been experimentally demonstrated.

In this paper, a bulk-micromachined three-axis accelerometer fabricated with commercial submicrometer CMOS wafers has been developed for low-cost realization of smart accelerometers and improvement of device performance. The signal processing circuits for three-axis detection were formed using a commercial 0.8-/spl mu/m CMOS technology. After that, micromachining processes were performed to the complete CMOS wafers to form accelerometer structures. The important technologies to separate micromachining processes from the CMOS process are wafer thickness control after CMOS fabrication and backside polishing with chemical spin etching. Accelerometers with 3/spl times/3 mm/sup 2/ and 6/spl times/6 mm/sup 2/ die size were fabricated with the developed fabrication technology. As a result of device evaluation, 2.0 mg/sub rms/ resolution of Z-axis acceleration, and 10.8 mg/sub rms/ resolution of X and Y-axis acceleration were obtained by the accelerometers with 6/spl times/6 mm/sup 2/ die size. Comparing for the same die area, the 6/spl times/6 mm/sup 2/ size accelerometer showed about 21.3 times higher resolution of Z-axis acceleration and 37.8 times higher resolution of X, Y-axis acceleration as compared to our previous three-axis accelerometer fabricated with 5.0-/spl mu/m CMOS technology. Temperature dependence and reliability for repetitive vibration loads were also evaluated. Through these evaluations, basic performance of the CMOS integrated three-axis accelerometer has been confirmed.

In this paper, the development of a bulk-micromachined CMOS integrated three-axis accelerometer which includes analog signal conditioning circuits is presented. The accelerometer was designed to simplify the signal processing tasks by incorporating a set of circuits for three-axis signal conditioning. This approach resulted in a 25% reduction of the circuit area. Stress-sensitive differential amplifiers (SSDAs) have been used as signal transducers, because they can be conveniently formed in a small area. The sensitivity and resolution of the fabricated devices realized in 8/spl times/8 mm/sup 2/ die area were 192 mV/g and 0.024 g for Z-axis acceleration, and 23 mV/g and 0.23 g for X and Y axis acceleration, respectively. The electrical noise component in the analog CMOS circuits was reduced by using a chopper stabilization technique. It was observed that there is a proper chopping clock frequency range to maximize the noise reduction effect. The noise of the SSDA was found to be related with the characteristics of CMOS differential amplifiers used. Typical temperature coefficient of sensitivity was about -2000 ppm//spl deg/C, which could be reduced to -320 ppm//spl deg/C or less by selecting a proper bias condition.