This paper presents the modeling, fabrication, and testing of a 3D-printed Coriolis mass flow sensor. The sensor contains a free-standing tube with a circular cross-section printed using the LCD ...3D-printing technique. The tube has a total length of 42 mm, an inner diameter of about 900 µm, and a wall thickness of approximately 230 µm. The outer surface of the tube is metalized using a Cu plating process, resulting in a low electrical resistance of 0.5 Ω. The tube is brought into vibration using an AC current in combination with a magnetic field from a permanent magnet. The displacement of the tube is detected using a laser Doppler vibrometer (LDV) that is part of a Polytec MSA-600 microsystem analyzer. The Coriolis mass flow sensor has been tested over a flow range of 0-150 g/h for water, 0-38 g/h for isopropyl alcohol (IPA), and 0-50 g/h for nitrogen. The maximum flow rates of water and IPA resulted in less than a 30 mbar pressure drop. The pressure drop at the maximum flow rate of nitrogen is 250 mbar.
This paper presents the first nickel-plated micro-Coriolis mass-flow sensor with integrated optical readout. The sensor consists of a freely suspended tube made of electroplated nickel with a total ...length of 60 mm, an inner diameter of 580 µm, and a wall thickness of approximately 8 µm. The U-shaped tube is actuated by Lorentz forces. An optical readout consisting of two LEDs and two phototransistors is used to detect the tube motion. Mass-flow measurements were performed at room temperature with water and isopropyl alcohol for flows up to 200 g/h and 100 g/h, respectively. The measured resonance frequencies were 1.67 kHz and 738 Hz for water and 1.70 kHz and 752 Hz for isopropyl alcohol for the twist and swing modes, respectively. The measured phase shift between the two readout signals shows a linear response to mass flow with very similar sensitivities for water and isopropyl alcohol of 0.41mdegg/h and 0.43 mdegg/h, respectively.
In this paper, a novel fabrication method is proposed for microfluidic tubes with a large diameter, circular cross-section, and thin wall. These properties make the tubes especially suitable for ...density sensors and Coriolis mass flow sensors, because of the resulting low tube mass, low-pressure drop, and low pressure-dependence of the tube shape. A demonstrator sensor was fabricated and the first measurement results of fluid density and mass flow are presented. The low-cost fabrication method is based on electroplating technology and results in tubes with a near-perfect circular cross-section. Diameters ranging from 120 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> to 1 mm and wall thicknesses from <inline-formula> <tex-math notation="LaTeX">8~\mu \text{m} </tex-math></inline-formula> to 60 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> have been achieved. For the demonstrator sensor presented in this paper a freely suspended tube was realized with a total length of 37 mm, a diameter of 600 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>, and a wall thickness of 20 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>. Density measurements were performed using various gases, liquids, and liquid mixtures at 21°C to 23°C lab temperature. The accuracy of the measured densities of gases such as nitrogen, argon, and helium is 5%. For liquids including DI water, isopropyl alcohol (IPA), and their various mixtures an accuracy of 0.5% was obtained. Preliminary mass flow rate measurements were performed with water and isopropyl alcohol up to 30 g/h with less than 30 mbar pressure drop thanks to the large tube diameter. 2021-0179
This paper presents a novel gas-independent thermal flow sensor chip featuring three calorimetric flow sensors for measuring flow profile and direction within a tube, along with a single-wire flow ...independent thermal conductivity sensor capable of identifying the gas type through a simple DC voltage measurement. All wires have the same dimensions of 2000 μm in length, 5 μm in width, and 1.2 μm in thickness. The design theory and COMSOL simulation are discussed and compared with the measurement results. The sensor's efficacy is demonstrated with different gases, He, N
, Ar, and CO
, for thermal conductivity and thermal flow measurements. The sensor can accurately measure the thermal conductivity of various gases, including air, enabling correction of flow rate measurements based on the fluid type. The measured voltage from the thermal conductivity sensor for air corresponds to a calculated thermal conductivity of 0.02522 W/m·K, with an error within 2.9%.
3D printing of soft EMG sensing structures enables the creation of personalized sensing structures that can be potentially integrated in prosthetic, assistive and other devices. We developed and ...characterized flexible carbon-black doped TPU-based sEMG sensing structures. The structures are directly 3D-printed without the need for an additional post-processing step using a low-cost, consumer grade multi-material FDM printer. A comparison between the gold standard Ag/AgCl gel electrodes and the 3D-printed EMG electrodes with a comparable contact area shows that there is no significant difference in the EMG signals' amplitude. The sensors are capable of distinguishing a variable level of muscle activity of the biceps brachii. Furthermore, as a proof of principle, sEMG data of a 3D-printed 8-electrode band are analyzed using a patten recognition algorithm to recognize hand gestures. This work shows that 3D-printed sEMG electrodes have great potential in practical applications.
Among the different techniques for monitoring the flow rate of various fluids, thermal flow sensors stand out for their straightforward measurement technique. However, the main drawback of these ...types of sensors is their dependency on the thermal properties of the medium, i.e., thermal conductivity (k), and volumetric heat capacity (ρcp). They require calibration whenever the fluid in the system changes. In this paper, we present a single hot wire suspended above a V-groove cavity that is used to measure k and ρcp through DC and AC excitation for both pure gases and binary gas mixtures, respectively. The unique characteristic of the proposed sensor is its independence of the flow velocity, which makes it possible to detect the medium properties while the fluid flows over the sensor chip. The measured error due to fluctuations in flow velocity is less than ±0.5% for all test gases except for He, where it is ±6% due to the limitations of the measurement setup. The working principle and measurement results are discussed.
Microfluidic pedestal nozzles have been fabricated using self-aligned wafer-scale microfabrication methods. Through implementation of these novel fabrication strategies, nozzles with a concentric rim ...at the nozzle exit were made. The process allows to accurately vary the rim radius, and rim radii ranging between 36μm and 111μm are reported here. A unique and essential feature of the nozzle, which is made of hydrophilic silicon dioxide, is that the rim edge has an interior angle of 5∘ and a radius of curvature smaller than 20 nm. Due to this nanometrically sharp rim edge, geometric contact line pinning of polar liquids is facilitated. With hydrostatic and hydrodynamic measurements, the nozzle functionality is demonstrated for water and ethanol. Due to the unprecedentedly strong contact line pinning, macroscopic contact angles can be increased by more than 150∘. These measurements reveal a pressure point at which the droplet starts to grow uninhibitedly, which is predicted by a thermodynamic model based on the Gibbs free energy of pinned droplets. It is reckoned that the nozzles are useful in applications where liquids with free surfaces have to be confined to a specific micron-sized surface area, as is the case in, e.g., inkjet printing and electrospinning. To show the functionality of the pedestal nozzles, electrohydrodynamic jetting of a typical electrospinning polymer solution is demonstrated.
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•Microfluidic pedestal nozzles have been fabricated using self-aligned wafer-scale microfabrication methods.•The nozzle exit has a rim edge with sub-20 nm radius of curvature and a 5∘ interior angle.•Due to contact line pinning at the sharp rim edge, droplets are confined to the nozzle rim.•Measurements show that the nozzles are functional for electrospinning of polymer solutions.
Sensing of the interaction forces at fingertips is of great value in assessment and rehabilitation therapy. Current force sensors are not compliant to the fingertip tissue and result in loss of touch ...sensation of the user. This work shows the development and characterization of a flexible fully-3D-printed piezoresistive shear and normal force sensor that uses the mechanical deformation of the finger tissue. Two prototypes of the sensing structure are evaluated using a finite element model and a measurement setup that applies normal and shear forces up to 10 N on a fingertip phantom placed inside the sensing structure, which is fixed to prevent slippage. Furthermore, the relation between strain (rate) and resistance of the conductive TPU, used for the strain gauges, is characterized. The applied normal and shear force components of the 3D-printed sensing structure can be partly separated. FEM analysis showed that the output of the sensor is largely related to the sensor geometry and location of the strain gauges. Furthermore, the conductive TPU that was used has a negative gauge factor for the strain range used in this study and might cause non-linear behaviors in the sensor output.
Aqueous‐Phase Reforming (APR) is a promising hydrogen production method, where biomass is catalytically reformed under high pressure and high temperature reaction conditions. To eventually study APR, ...in this paper, we report a high‐pressure and high‐temperature microfluidic platform that can withstand temperatures up to 200°C and pressures up to 30 bar. As a first step, we studied the phase transition of four typical APR biomass model solutions, consisting of 10 wt% of ethylene glycol, glycerol, xylose or xylitol in MilliQ water. After calibration of the set‐up using pure MilliQ water, a small increase in boiling point was observed for the ethylene glycol, xylitol and xylose solutions compared to pure water. Phase transition occurred through either explosive or nucleate boiling mechanisms, which was monitored in real‐time in our microfluidic device. In case of nucleate boiling, the nucleation site could be controlled by exploiting the pressure drop along the microfluidic channel. Depending on the void fraction, various multiphase flow patterns were observed simultaneously. Altogether, this study will not only help to distinguish between bubbles resulting from a phase transition and/or APR product formation, but is also important from a heat and mass transport perspective.
Transient nanobubbles in short-time electrolysis Svetovoy, Vitaly B; Sanders, Remco G P; Elwenspoek, Miko C
Journal of physics. Condensed matter,
2013-May-08, Letnik:
25, Številka:
18
Journal Article
Recenzirano
Odprti dostop
Water electrolysis in a microsystem is observed and analyzed on a short-time scale of ∼10 μs. The very unusual properties of the process are stressed. An extremely high current density is observed ...because the process is not limited by the diffusion of electroactive species. The high current is accompanied by a high relative supersaturation, S > 1000, that results in homogeneous nucleation of bubbles. On the short-time scale only nanobubbles can be formed. These nanobubbles densely cover the electrodes and aggregate at a later time to microbubbles. The effect is significantly intensified with a small increase of temperature. Application of alternating polarity voltage pulses produces bubbles containing a mixture of hydrogen and oxygen. Spontaneous reaction between gases is observed for stoichiometric bubbles with sizes smaller than ∼150 nm. Such bubbles disintegrate violently affecting the surfaces of the electrodes.
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