An electro wetting on dielectrics - system utilizing two different dielectric layers

Electrowetting on dielectrics is an established actuation principle in digital microfluidics. The Lippmann-Young equation describes the dependence of the contact angle to applied voltages. At high voltages the changes of the contact angle diminish and the contact angle saturates. Several theories try to explain that phenomenon. Amongst others, trapped charges and leak currents were proposed as the mechanisms behind the contact angle saturation. In this paper, we will combine these two theories to a common one and show that leak current and dielectric breakdown causes trapped charges and leads to a deviation of the Lippmann-Young equation and to a non-constant but oscillating contact angle at increasing voltages. The thermodynamic derivation takes into account the electrostatic energy of a perfect capacitor, consisting of a homogeneous or a layered dielectric isolation. In our contribution, we show that isolation layers consisting of real materials with non-zero conductivities and, especially in the case of dielectric breakdown in one of these layers, display electrostatic energies different from that of an ideal capacitor. Thus, the contribution to the surface energies changes and the wetting contact angle differs from the Lippmann-Young prediction. It turns out, that the change of the surface energy of a solid to liquid interface differs depending on the order of the applied dielectric layers

Fully Screen Printed Carbon Black-Only Thermocouple and the Corresponding Seebeck Coefficients

This work presents a thermocouple that is fully screen printed and consists exclusively of carbon black conductors. Two different carbon black inks were printed to form a thermocouple, which has been characterized regarding its output voltage. For reference, each of the carbon black inks was used in combination with gold to form two further thermocouples. These have also been characterized and the output voltage used to predict the output of the associated thermocouple consisting of pure carbon black conductors. The results have been compared with the measurement results and show that the output of the pure carbon black thermocouple is roughly 10% lower than expected

Screen printed electrodes for capacitive level sensors

Článek popisuje výrobu a charakterizaci nízkonákladových elektrod pro kapacitní senzory výšky hladiny realizovaných na flexibilním substrátu. Cílem bylo připravit vodivé elektrody tiskem stříbrné nebo PEDOT:PSS pasty na ovrstvenou PET folii. Jednotlivé kapacitory ve formě interdigitálních elektrod byly navrženy s různými vzdálenostmi / tloušťkami prstů od 300/300 μm do 800/800 μm, a délkou prstů 10 mm a 15 mm a celkovou délkou 100 mm. Natisknuté struktury byly tepelně zalaminovány krycí a ochrannou PET vrstvou. Citlivost vyrobených struktur byla charakterizována v tekutinách s různou relativní permitivitou a vodivostí (voda a olej). Největší naměřená citlivost byla 0.7 pF/mm pro vodu a 0.08pF/mm pro olej.The paper reports on the fabrication and characterization of low-cost electrodes for capacitive level sensors realized on a flexible substrate. The aim is to prepare conductive electrodes by printing of silver and PEDOT:PSS pastes on coated PET foil. Individual capacitors in the form of interdigital electrodes (IDT) were designed with different finger width/spacing dimensions from 300/300 μm to 800/800 μm, a finger length 10 mm and 15 mm and an overall length of 100 mm. The printed structures were thermally laminated with covering PET foil. The sensitivity of the fabricated devices was characterized in liquids with different relative permittivity and conductivity (water and oil). The highest measured sensitivity was 0.7 pF/mm and 0.08pF/mm for water and oil respectively

Embedded, Fully Spray-Coated Pressure Sensor Using a Capacitive Transducing Mechanism

Embedding functional sensor layers directly into mechanical systems in heavy-duty surroundings facilitate the real-time monitoring of the system’s state. This work presents a fully-spray coated pressure sensor that is suitable for applications in the high pressure range. It is embedded into functionalized organic coatings that additionally act as a dielectric for the capacitive sensing mechanism. The sensitivity of the sensor, as well as its long-time stability, has been determined. Additionally, testing has been performed at elevated temperatures to determine the temperature dependent sensitivity that arises from the temperature dependence of the Young’s moduli

Screen-Printed, Pure Carbon-Black Thermocouple Fabrication and Seebeck Coefficients

Thermocouples classically consist of two metals or semiconductor components that are joined at one end, where temperature is measured. Carbon black is a low-cost semiconductor with a Seebeck coefficient that depends on the structure of the carbon particles. Different carbon black screen-printing inks generally exhibit different Seebeck coefficients, and two can therefore be combined to realize a thermocouple. In this work, we used a set of four different commercially available carbon-black screen-printing inks to print all-carbon-black thermocouples. The outputs of these thermocouples were characterized and their Seebeck coefficients determined. We found that the outputs of pure carbon-black thermocouples are reasonably stable, linear, and quantitatively comparable to those of commercially available R- or S-type thermocouples. It is thus possible to fabricate thermocouples by an easily scalable, cost-efficient process that combines two low-cost materials.(VLID)344801

A Spray Processed Polymer-Based High Temperature Organic/Metal Thermocouple for Embedding in Organic Coatings of Steel Substrates

In this work we present the realization of a fully spray processed embedded temperature sensor. The sensing element is a thermocouple made of conductive materials which are high temperature stable polymer based paints with organic or metallic filler particles. The thermocouple is embedded in an organic paint layer which shows, besides good high temperature properties up to 250 °C, excellent mechanical and chemical stability. The manufactured thermocouples are tested up to a junction temperature of 250 °C, first without and afterwards with an encapsulation layer. The measured output voltage for a terminal temperature of 25 °C and a junction temperature of 250 °C is in the region of 4.23 mV before and after top coating. Finally, a layer analysis of the encapsulated device is made using a cross-section polish