Thermal Flow Measurements by a Flexible Sensor, Implemented on the External Surface of the Flow Channel

AbstractA thermal gas flow sensor was developed and evaluated. The presented implementation requires only low-cost manufacturing techniques and readily available components, while maintaining a high level of detection range and sensitivity. Heater and sensing elements were integrated on a flexible substrate and the device was formed by bending the substrate so that the active elements were placed on the external surface of the formed channel, therefore zero flow interference is achieved and a wide variety of fluids can be measured without compromising the sensor integrity. Evaluation was made using air flow rates in the range of 0-65SLPM utilizing electrical measurements and IR imaging techniques simultaneously

Study and Evaluation of a PCB-MEMS Liquid Microflow Sensor

This paper presents the evaluation of a miniature liquid microflow sensor, directly integrated on a PCB. The sensor operation is based on the convective heat transfer principle. The heating and sensing elements are thin Pt resistors which are in direct electrical contact with the external copper tracks of the printed circuit board. Due to the low thermal conductivity of the substrate material, a high degree of thermal isolation is obtained which improves the operating characteristics of the device. The sensor is able to operate under both the hot-wire and the calorimetric principle. In order to fully exploit the temperature distribution in the flowing liquid, multiple sensing elements are positioned in various distances from the heater. A special housing was developed which allowed implementation of the sensor into tubes of various cross sectional areas. The sensor sensitivity and measurement range as a function of the sensing element distance were quantified. A minimum resolution of 3 μL/min and a measurement flow range up to 500 μL/min were achieved

A Review on Humidity, Temperature and Strain Printed Sensors—Current Trends and Future Perspectives

Printing technologies have been attracting increasing interest in the manufacture of electronic devices and sensors. They offer a unique set of advantages such as additive material deposition and low to no material waste, digitally-controlled design and printing, elimination of multiple steps for device manufacturing, wide material compatibility and large scale production to name but a few. Some of the most popular and interesting sensors are relative humidity, temperature and strain sensors. In that regard, this review analyzes the utilization and involvement of printing technologies for full or partial sensor manufacturing; production methods, material selection, sensing mechanisms and performance comparison are presented for each category, while grouping of sensor sub-categories is performed in all applicable cases. A key aim of this review is to provide a reference for sensor designers regarding all the aforementioned parameters, by highlighting strengths and weaknesses for different approaches in printed humidity, temperature and strain sensor manufacturing with printing technologies

Flexible PCB-MEMS Flow Sensor

AbstractA flexible gas flow sensor was developed and characterized. The sensor was fabricated on a flexible PCB substrate and is able to quantify flow rate based on the thermal transfer principle. Direct electrical communication to the macroworld is achieved, while the effective thermal isolation enhances sensor performance. Characterization in the range of 1-10 SLPM is presented

Multipurpose thermal sensor based on Seebeck effect

This paper reports a multipurpose thermal sensor based on the Seebeck effect. The sensor has thermocouples with a multilayer structure consisting of one thermocouple strip laying on the insulating membrane and the other one under the first thermoelement and the membrane. The vertical arrangement allows a greater number of thermocouples to be placed on a given chip area. Central and lateral thermistors are placed near hot and cold thermocouple junctions, respectively, and serve for determination of the temperature difference established on the chip. Experimental results confirm that the same structure could be used as a thermal converter and a gas flow meter.12-15 May 2002, Niš, Yugoslavi

Study of flow and pressure field in microchannels with various cross-section areas

In this work a micro-flow sensor integrated in the bottom surface of a rectangular microchannel is used in order to evaluate simultaneously both the flow velocity and the pressure in various micro-flow conditions. In this way direct flow rate measurement is achieved while real-time monitoring of the corresponding flow and pressure values are obtained. The effect of the microchannel dimensions in the flow determination is also studied. An almost linear relation of Delta P/L with respect to Re was extracted, which indicates a laminar flow behavior. The friction factor, corresponding to the specific microchannel dimensions was calculated together with the f.Re value

A Disposable Inkjet-Printed Humidity and Temperature Sensor Fabricated on Paper

In this work we present the development of a low-cost humidity and temperature sensing platform on paper by inkjet printing, using a commercial AgNPs conductive ink. The humidity sensing module was capable of measuring relative humidity in the range of 0⁻90%rH, exhibiting linear response with minimal memory effect when returning to 0%rH baseline signal while the temperature sensor performed linearly as well in the range of 25⁻75°C. Process repeatability has been verified by electrical and optical characterization. Mechanical bending results highlight the platform’s capability to serve as an easy to install, flexible multi-parametric sensing platform

Design of a Mass Air Flow Sensor Employing Additive Manufacturing and Standard Airfoil Geometry

This work concerns the design, fabrication, and preliminary characterization of a novel sensor for determining the air intake of low and medium power internal combustion engines employed at various applications in the marine industry. The novelty of the presented sensor focuses on the fabrication process, which is based on additive manufacturing combined with PCB technology, and the design of the sensing elements housing geometry, which is derived through suitable CFD simulations and is based on standard airfoil geometry. The proposed process enables low-cost, fast fabrication, effective thermal isolation, and facile electrical interconnection to the corresponding circuitry of the sensor. For initial characterization purposes, the prototype device was integrated into a DIESEL engine testbed while a commercially available mass air flow sensor was employed as a reference; the proper functionality of the developed prototype has been validated. Key features of the proposed device are low-cost, fast on-site manufacturing of the device, robustness, and simplicity, suggesting numerous potential applications in marine engineering

A Bioelectronic System to Measure the Glycolytic Metabolism of Activated CD4+ T Cells

The evaluation of glucose metabolic activity in immune cells is becoming an increasingly standard task in immunological research. In this study, we described a sensitive, inexpensive, and non-radioactive assay for the direct and rapid measurement of the metabolic activity of CD4+ T cells in culture. A portable, custom-built Cell Culture Metabolite Biosensor device was designed to measure the levels of acidification (a proxy for glycolysis) in cell-free CD4+ T cell culture media. In this assay, ex vivo activated CD4+ T cells were incubated in culture medium and mini electrodes were placed inside the cell free culture filtrates in 96-well plates. Using this technique, the inhibitors of glycolysis were shown to suppress acidification of the cell culture media, a response similar to that observed using a gold standard lactate assay kit. Our findings show that this innovative biosensor technology has potential for applications in metabolic research, where acquisition of sufficient cellular material for ex vivo analyses presents a substantial challenge