Sensors and Actuators最新文献

Ion-sensitive field effect transistors (ISFETs) have been successfully introduced into a titration system for flow injection analysis (FIA). The influence of the titration parameters of the ISFET-FIA system is discussed and experimentally studied. Various kinds of acid-base titration have been tested. There exists a good linearity between t_eq (titration time) and log C⁰₂ (concentration of analysed substance), with a regression coefficient better than 0.9997. The titration can be done at a rate of up to 75 samples per hour. The reverse titration method can extend the detection limit down to 5 × 10⁻⁴ M of the analysed substance.

An SPE (solid polymer electrolyte)-based solid-state electrochemical oxygen gas sensor is reported. A hydrophobic Teflon-bonded Pt back layer pressed on a piece of Nafion membrane serves as the working (sensing) electrode, with a diffusion-controlling capillary in front. The sensor exhibits fast response, small temperature coefficient and long-term stability.

An integrated multifunction sensor based on heat transfer at a constant chip temperature (CCT) has been fabricated by a conventional CMOS process. It consists of a temperature-sensing stage for the measurement of the chip temperature, a CMOS operational amplifier for amplification and control, and a heating branch circuit to heat the sensor chip. All three parts are integrated on one chip and connected to form a negative feedback loop for CCT operation. Using this sensor, measurements of flow velocity, temperature and vacuum have been made. The heating power of the chip is used to indicate those measurands that affect the heat transfer between the chip and the ambient. When used for flow measurements, the sensor demonstrates high sensitivity and a large output level (500 mV output at V_f=50 cm/s, N₂, and T_cT_a=15°C). It can be used to measure both gas and liquid flor velocities. The sensor shows a sensitivity of −64 mV/°C when used for temperature measurements and it has the advantage of much easier design of on-chip signal processing circuits over conventional temperature sensors since the chip temperature is kept constant. When used as a vacuum sensor, experiments show that the vacuum range from atmospheric pressure to 10⁻¹ Torr produces an output change of about 300 mV. Lower pressures can also be measured without any problems.

In this paper, a new method for porosity control of porous humidity-sensitive ceramics is presented. Graphite powder is chosen as the pore former. It is convenient to control the pore size and porosity of porous humidity-sensitive ceramics made from CoFe spinel and MgCr spinel by changing the content and grain size of the pore former. The electrical behaviours can be kept stable for a long time because of the completeness of the solid phase reaction. Experiments indicate that when the weight percentage of graphite is 10–20 wt.%, the humidity sensitivity of these two porous ceramics increases remarkably and the linearity of the resistance and humidity characteristics is clearly improved. It has been shown by XRD, SEM and AES analyses that graphite powder has only a slight influence on the matrix material, but its pore-forming effects are quite favourable. From the electronic—ionic comprehensive conduction model, and use of Grotthuss' transmission mechanism and the phase law of two mixed phases, a new equation of resistance and humidity has been derived theoretically, thus successfully explaining the experimental data. Moreover, the characteristics of resistance and humidity, and those of capacitance and humidity of various types of materials can be determined.

A new sputtered amorphous thin-film pressure transducer is presented. Both the transducer and the material of the amorphous Ni₆₈Si₁₅B₁₇ alloy were developed in our laboratory. The properties of the amorphous alloy are introduced including: (1) the dependence of fractional changes in electrical resistance on the tensile stress; (2) the dependence of electrical resistance on temperature; (3) the behaviour of ΔR/R₀=f(σ) after annealing for two hours at 200 °C. The construction, static characteristics and dynamic characteristics of the pressure transducer are then introduced. Many dynamic mathematical models and the dynamic performance of the pressure tranducer are described.

A new multifunctional sensitive ceramic, BaTiO₃BaSnO₃ (BTS), which is a p-type metal-oxide porous ceramic semiconductor, has been studied. It is capable of detecting temperature, humidity and gas type with a single sensing element. This paper presents results of research on multifunctional sensitive ceramics. The crystalline phase, porous structure, semiconducting properties and the relationships between the sensitive characteristics and the meso-macrostructure of the pores of BTS porous ceramics have been investigated.

Signal superimposition for silicon pressure transducers is an approach to make full use of the vast area available on silicon diaphragms to boost signal output, to eliminate the sensitivity to a magnetic field for transverse-voltage type pressure sensors and some other possible applications. Three types of signal superimposition methods are proposed here and a monolithic integrated circuit pressure transducer using active amplifiers is presented.

A newly designed thermal biosensor (TBS) is reported. It is constructed by integrating a temperature sensor with a bioreactor, which can be easily dismantled. Such a design makes the TBS versatile. Both differential and adiabatic techniques are used to improve its precision and resolution. As an example of application, a glucose assay is described: resolution 2 × 10⁻⁸ mol, linear range 2 × 10⁻⁸ mol−1.7 × 10⁻⁶ mol, relative error < 6%, lifetime more than one month and sample volume 4 × 10⁻² ml.

A high-resolution encapsulation procedure suitable for chemical sensors has been developed. It is based on the electrochemical generation of a poly-(oxyphenylene) film at the electrically active areas of the device. The 1.5 to 5 μ thick encapsulation film is selectively deposited on gold, platinum or carbon surfaces. No deposition takes place on aluminium, which allows this metal to be used as a mask. The resistivity of a 2 μm thick film after a four-week exposure to 0.1 M NaCl is 7 × 10¹¹ Ω cm.