Integrated Flow Sensor Research Articles

Invention of Device for Measuring Cardiac Compression Rates and the Depth for the Cardio-Pulmonary Resuscitation Manikin

Manikins that simulate cardiopulmonary resuscitation (CPR) are used to teach personnel how to execute it. Modern cardiac resuscitation manikins are still low-fidelity designs in terms of anatomy and physiology. Designing a manikin with a cardiac and respiratory system, as well as integrated flow sensors to track cardiac output and air displacement in response to cardiopulmonary resuscitation, was the main goal of this research. A polyoxy-methylene rib cage joined to a vertebral column from an anatomical female model was used to create this manikin in line with anatomical proportions. The respiratory system was made up of a polyvinyl chloride bronchus, a latex trachea, and silicon-coated memory foam that mimicked lungs. The pulmonary and aortic arteries were represented by two sets of latex tubing, while the ventricles and aggregated abdominal volumes were represented by latex balloons, respectively. These components made up the cardiovascular system. These balloons were inserted into polyether foam and filled with blood from a life/form simulation. Flow sensors were installed in the respiratory and cardiovascular systems to collect data in reaction to chest compressions. On this manikin, three non-medical individuals applied chest compressions that produced data proportional to force-displacement while the flow sensors supplied feedback. The force-displacement experiments performed on this manikin demonstrate an advantageous nonlinear behavior that mimics the chest compressions used during cardiopulmonary resuscitation in humans. A considerable amount of information on the internal effects of cardiopulmonary resuscitation is also provided by the flow sensors. To sum up, scientifically developed and anatomically accurate designs of cardiopulmonary resuscitation manikins that incorporate flow sensors can enhance physiological fidelity and offer helpful feedback data.

In Vitro Study on Smart Stent for Autonomous Post-Endovascular Aneurysm Repair Surveillance

Endovascular aneurysm repair (EVAR) is an established and reliable surgical treatment of abdominal aortic aneurysm (AAA), where a covered stent is implanted to prevent blood flow in the aneurysm sac. Although current EVAR is an effective technique, it requires long-term monitoring for the post-operative complications (e.g., endoleak, stent occlusion), which usually requires expensive radiologic imaging techniques such as ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI). In this paper, we present an accessible and continuous post-EVAR surveillance scheme by developing a smart stent that features ultrasonic powering, blood flow sensing, and integrated wireless electronics. As the body of the smart stent, a piezoelectric membrane with a custom pore architecture is utilized. The benefits of the embedded pore architectures include the expansion and contraction to comply with a minimally invasive procedure and enhanced ultrasonic powering and sensing capability. The smart stent is able to expand up to 112% in diameter when stretched due to the negative Poisson's ratio. The ultrasound generates 0.23 mW of electrical power, which can sufficiently operate a low power wireless electronics. A comprehensive operation of the smart stent is demonstrated in vitro. The integrated flow sensor can measure blood flow ranging between 30 mL/min to 980 mL/min with an average sensitivity of 0.11 mV/mL/min. The wireless electronics transmit and receive such blood flow rate data by modulating the carrier frequency from 81 to 88 MHz from 1 m away. The developed smart stent prototype is the first step towards minimizing post-EVAR complications by providing early and frequent access to diagnostic information to patients and physicians.

Evaluation of a novel flow-controlled syringe infusion pump for precise and continuous drug delivery at low flow rates: a laboratory study.

Syringe infusion pumps are used for the administration of short-acting drugs in anaesthesia and critical care medicine, but are prone to flow irregularities at low flow rates. A flow-controlled syringe infusion pump using an integrated flow sensor for feedback control represents a new approach to overcoming these limitations. This study compares the performance of a prototype flow-controlled syringe pump both at start-up, and during vertical displacement manoeuvres, with that of a standard infusion syringe pump. The novel pump almost completely eliminated delays at start-up and flow irregularities during hydrostatic pressure changes. Related fluctuations in plasma drug concentration were minimised and the known disadvantages of standard syringe infusion pumps currently used in clinical practice were reduced. Besides providing fast start-up to steady-state flow and precise continuous drug delivery at low flow rates during hydrostatic pressure changes, the new pump offers the potential for the development of target-controlled infusion algorithms for short-acting cardiovascular and other drugs.

Fabrication process for inexpensive, biocompatible and transparent PCBs. Application to a flow meter

The requirements of the Printed Circuit Boards (PCBs) are gradually more demanding due to the advances on the technology of many fields. Some of these requirements are biocompatibility and transparency for biological/biomedical applications. In this paper, the fabrication of inexpensive, biocompatible and transparent substrate for rapid prototyping is reported. This substrate is intended to be used as PCB because of their similarities. It is composed of polymethylmetacrylate (PMMA) as substrate, aluminum (Al) as conductive material and a light cure acrylic biocompatible adhesive to perform the bonding between the aluminum and the substrate. In addition, a solder mask layer of the same adhesive is performed to cover the aluminum tracks. The process is easy to perform and inexpensive if taking into account the used materials and the facilities. In this respect, a conventional UV light source is needed. Taking into account these requirements, a rapid prototyping of a PCB-based flow meter is developed as an example of application. This flow meter is fabricated using the proposed PCB substrate. This device is intended to be integrated on transparent and rapid prototyping lab on chip devices for biomedical applications. This integration implies the compatibility of this flow meter with optical sensing of biological samples. The flow sensor is composed of a microheater with a range of temperature from room temperature up to 100°C. The fabricated microheater is used as PTC resistor to develop the highly integrated flow sensor. The proposed device has a sensitivity of 450μV/(μL/min) and a normalized sensitivity of 450ppm/(μL/min) for a driven current of 0.6A. The range of flow rate of the fabricated device lies between 0 and 450μL/min.

An innovative design for cardiopulmonary resuscitation manikins based on a human-like thorax and embedded flow sensors.

Cardiopulmonary resuscitation manikins are used for training personnel in performing cardiopulmonary resuscitation. State-of-the-art cardiopulmonary resuscitation manikins are still anatomically and physiologically low-fidelity designs. The aim of this research was to design a manikin that offers high anatomical and physiological fidelity and has a cardiac and respiratory system along with integrated flow sensors to monitor cardiac output and air displacement in response to cardiopulmonary resuscitation. This manikin was designed in accordance with anatomical dimensions using a polyoxymethylene rib cage connected to a vertebral column from an anatomical female model. The respiratory system was composed of silicon-coated memory foam mimicking lungs, a polyvinylchloride bronchus and a latex trachea. The cardiovascular system was composed of two sets of latex tubing representing the pulmonary and aortic arteries which were connected to latex balloons mimicking the ventricles and lumped abdominal volumes, respectively. These balloons were filled with Life/form simulation blood and placed inside polyether foam. The respiratory and cardiovascular systems were equipped with flow sensors to gather data in response to chest compressions. Three non-medical professionals performed chest compressions on this manikin yielding data corresponding to force–displacement while the flow sensors provided feedback. The force–displacement tests on this manikin show a desirable nonlinear behaviour mimicking chest compressions during cardiopulmonary resuscitation in humans. In addition, the flow sensors provide valuable data on the internal effects of cardiopulmonary resuscitation. In conclusion, scientifically designed and anatomically high-fidelity designs of cardiopulmonary resuscitation manikins that embed flow sensors can improve physiological fidelity and provide useful feedback data.

Transport of the high-risk neonate

Neonatal transport is continuously evolving and has developed to a cornerstone of modern perinatal medicine. Although the regionalization of perinatal care and delivery of high-risk neonates in appropriately designed centres improves neonatal outcome, neonatal transport represents an invaluable resource in order to guarantee tertiary level care throughout the region. A highly trained, adequately skilled and well-equipped transport team is key in order to provide a good quality of care for a wide variety of clinical disorders and their potential complications. A safe and efficient neonatal transport begins in the referring hospital. An optimal communication between the referring team and the transport team is paramount. Besides collecting information the transport team may advise the referring team about specific steps to undertake until arrival [1]. Adequate resuscitation and effective stabilization improve survival and reduce the chances of deterioration during transport, especially in critically ill neonates with limited physiological reserves [2]. High risk conditions like pneumothorax, congenital diaphragmatic hernia, oesophageal atresia, cardiac malformations, abdominal wall and neural tube defects and hypoxic ischemic encephalopathy (HIE) are still life threatening and require highly specialized care and monitoring [3]. The equipment routinely used for monitoring in the neonatal intensive care unit (NICU) is not specifically designed for transport and may not function properly under transport conditions. However, standard monitoring including temperature, ECG, pulse oximetry and CO2-monitoring should be routinely provided [4]. Delivering adequate ventilatory support including the administration and measurement of iNO may be challenging. A ventilator with an integrated flow sensor is helpful to assess respiratory function. The recommended ventilatory strategies in the NICU like volume-targeted ventilation can minimize lung damage and maintain more stable paCO2 values. There is a strong physiological rationale supporting the use of pre-heated and humidified air in ventilated infants, since it reduces trauma to the respiratory epithelium and is helpful to stabilize the body temperature [5,6]. Pharmacologic management including catecholamines, prostaglandins and analgosedation via multiline infusions may be necessary, thus rendering difficult situations still more complex. Active or passive body cooling in case of HIE is often demanding. Adequate protocols and an optimal temperature control to avoid accidental hyper- or hypothermia are essential [7]. In literature, data on high-risk transports are lacking, likely because of the difficulty to perform randomized studies in this field. Advanced training in resuscitation and stabilization of the neonate, as well as a specific transport and simulation based team training are mandatory for all personnel.

High Precision Bidirectional Heat Pulsed Flow Sensor

In this work we have designed and simulated a thermal bi-directional integrated circuit mass flow sensor. The approach used here was an extension to the gas flow model given by Mayer and Lechner [1]. The design features high precision response received from analog integrated circuits. An established mathematical model for the heat flow equation including CFD parameters were used within COMSOL simulation (COMSOL Multiphysics, Sweden). Heat pulses of 55°C for a period of nearly 120 seconds and 50% duty cycles were applied as thermal sources to the flowstream. The boundary conditions of the heat equations at the solid (heating element) fluid interface were set up in the software for the thermal response. The hardware design included one heating element and two sensing elements were used to detect the bi-directional mass flow. Platinum sensors were used due to their linear characteristics within 0°C to 100°C range, and their high temperature coefficient (0.00385 Ω/°C). Polyimide thin film heater was used as the element due to its high throughput and good thermal efficiency. Two bridge circuits were used to sense the temperature distribution in the vicinity of the sensing elements.

High-temperature zirconia microthruster with an integrated flow sensor

This paper describes the design, fabrication and characterization of a ceramic, heated cold-gas microthruster device made with silicon tools and high temperature co-fired ceramic processing. The device contains two opposing thrusters, each with an integrated calorimetric propellant flow sensor and a heater in the stagnation chamber of the nozzle. The exhaust from a thruster was photographed using schlieren imaging to study its behavior and search for leaks. The heater elements were tested under a cyclic thermal load and to the maximum power before failure. The nozzle heater was shown to improve the efficiency of the thruster by 6.9%, from a specific impulse of 66 to 71 s, as calculated from a decrease of the flow rate through the nozzle of 13%, from 44.9 to 39.2 sccm. The sensitivity of the integrated flow sensor was measured to 0.15 mΩ sccm−1 in the region of 0–15 sccm and to 0.04 mΩ sccm−1 above 20 sccm, with a zero-flow sensitivity of 0.27 mΩ sccm−1. The choice of yttria-stabilized zirconia as a material for the devices makes them robust and capable of surviving temperatures locally exceeding 1000 °C.

Ultrasound Flow Sensor Based on Arrays of Piezoelectric Transducers Integrated in a Composite

The functionalization of fiber-reinforced polymer composites by integration of piezoelectric transducers allows for both the measurement and the excitation of guided waves within the component. A common use for guided waves in composite components is nondestructive examination. In the presented work, however, the radiation of ultrasound waves from the surface of the component due to guided waves in the component is utilized. Glass fiber-reinforced polypropylene (GF/PP) plates with integrated arrays of piezoelectric macro fiber composite (MFC) transducers are used as ultrasound transmitter and receiver. The plates are then set up as facing walls of a rectangular duct and the sound transit times between the plates are measured. From the measured sound transit times, the velocity of gas flow inside the composite duct is determined. In that way, a flow sensor integrated in the walls of a flow channel, e.g. an air duct, made of composites is built. This paper focuses on the manufacturing of such an integrated flow sensor.

Integration of nanosensors into a sealed microchannel in a hybrid lab-on-a-chip device

Commonly used assembly methods for microfluidic devices rely heavily on direct, manual bonding of different components with limited visual aids. The manual operation is likely to cause damage to existing structures, especially to nanoscale sensors on the substrate. Here we report a novel approach to integrate nanosensors into a lab-on-a-chip device with total elimination of operational errors from the manual bonding process. The microfluidic components are composed of an ultraviolet (UV) light-defined, cross-linked SU-8 microchannel and a polydimethylsiloxane (PDMS) top cover. The hybrid microfluidic structure provides a fully sealed microchannel and precisely positioned features. Well-organized single-walled carbon nanotube (SWNT) thin films are deposited and aligned across the electrodes on a silicon substrate with dielectrophoresis. The assembly of SWNTs is carried out in a sealed microchannel which eliminates the potential damage of the nanosensors during the bonding process. The SWNT devices are configured as two-terminal resistor-type sensors with the metal electrodes as the probing pads and the dielectrophoretically captured SWNTs as the sensing elements. To demonstrate the feasibility of this integration approach, an assembled SWNT device is measured as an integrated flow sensor to monitor the flow rate in the microchannel. This lab-on-a-chip device is designed as a platform that can be expanded for more applications. For example, with minimal modifications, the device can be used in chemical sensing, biosensing, and medical research.

A Silicon Micropump with On-Chip Flow Meter

This paper presents a novel architecture micropump based on a piezoelectric actuation with active valves and an integrated flow sensor. The in-built flow sensor is based on the pressure differential measurement using four strain gauges located on two new membranes arranged in a unique single Wheatstone bridge. The experimental characterization of the flow sensor fitted well with the theory. Additionally, it showed that our built-in sensor gives useful information about the instantaneous flow rate throughout the pump compared to an external flow-meter.

Monolithic Integration of a Micromachined Flow Sensor based on Post-CMOS

Abstract This paper investigates design, fabrication and testing of a monolithic piezoresistive flow sensor with on-chip signal conditioning circuit. Post-CMOS Processing of this flow sensor will be the focus of this paper, starting from theoretical analysis and numerical simulation, and moving to experimental verification. The flow sensor presented here is comprised of four symmetrically arranged silicon diaphragms with piezoresistors on them used to sense the drag force induced by the input gas flow. Piezoresistor fabrication has been merged into a conventional CMOS process and releasing of sensing part is conducted after CMOS processing. An integrated flow sensor with on-chip CMOS circuitry fabricated using this novel post-CMOS process was fabricated and tested. The integration method shows good compatibility of MEMS process with the state of art CMOS process. A quadratic relation between output voltage and flow rate was obtained within flow rate of 0-5L/min and the testing result was then compared with an Inter-CMOS based flow sensor.

Fabrication and characterization of a directional anemometer based on a single chip MEMS flow sensor

A compact anemometer based on integrated flow sensors is presented. The device exploits a recently proposed approach, by which the pressure induced on the lateral surface of a cylinder exposed to the wind is converted into two air flow rates exhibiting sinusoidal dependence on the wind direction. A significant size reduction and assemblage simplification were achieved by sensing the two flows by means of a double channel flow meter, integrated on a single silicon chip. The results of measurements, performed over a wind velocity range 0.4–7.9m/s, demonstrated the effectiveness of the proposed anemometer.

Fabrication of monolithically integrated flow sensor on tube

A monolithic-type flow sensor was developed to simplify the packaging process for microelectro mechanical system (MEMS) fluidic devices. In our design, a heater element for sensing flows as part of a thermal flow sensor was formed on the outside surface of a thin film in a tube, enabling us to connect electrical wiring from it to the outside of the tube directly. The monolithic-type flow sensor was produced by applying photolithography on a cylinder surface and transferring a cylindrical parylene film structure to the outside of the skeleton tube by using an adhesive heat-shrinkable tube. The relationship between the input power of the sensor and the flow rate obeyed King's equation under the flow conditions for 0–2000 sccm. The response time of 116 ms, which is comparable to that of commercially available mass flow controllers, was obtained.

Monolithic integration of a micromachined piezoresistive flow sensor

In this paper, a monolithic integrated piezoresistive flow sensor is presented, which was fabricated with an intermediate CMOS (complementary metal-oxide semiconductor) MEMS (micro electro mechanical system) process compatible with integrated pressure sensors. Four symmetrically arranged silicon diaphragms with piezoresistors on them were used to sense the drag force induced by the input gas flow. A signal conditioning CMOS circuit with a temperature compensation module was designed and fabricated simultaneously on the same chip with an increase of the total chip area by only 35%. An extra step of boron implantation and annealing was inserted into the standard CMOS process to form the piezoresistors. KOH anisotropic etching from the backside and deep reactive ion etching (DRIE) from the front side were combined to realize the silicon diaphragms. The integrated flow sensor was packaged and tested. The testing results indicated that the addition of piezoresistor formation and structure releasing did not significantly change any of the circuitry characteristics. The measured sensor output has a quadratic relation with the input flow rate of the fluid as predicted. The tested resolution of the sensor is less than 0.1 L min−1 with a measurement range of 0.1–5 L min−1 and the sensitivity is better than 40 mV per (L min−1) with a measurement range of 4–5 L min−1. The measured noise floor of the sensor is 21.7 µV rtHz−1.

Design and analysis of integrated flow sensors by means of a two-dimensional finite element model

A model capable of providing quantitative predictions about the response of integrated thermal flow sensors is presented. The proposed approach exploits the versatility of the FEMLAB™ environment to introduce elements of a 3D description into a more computationally efficient 2D model. The simulations described in this work were aimed to check the consistence of the model with measurements performed on a real sensor and evaluate the actual benefits of changing some geometrical parameters with respect to the original configuration.

A Closed-Loop Mass Flow Controller Based on Static Solid-State Devices

A mass flow controller, based on an integrated flow sensor and a thermally actuated solid state regulator, is presented. The sensor is a miniaturized differential calorimeter obtained by postprocessing a silicon chip fabricated by a standard microelectronic process. The regulator consists in a microchannel etched into the surface of a silicon substrate and sealed with a glass plate, joined to the silicon die using anodic bonding. Flow regulation is achieved by varying the channel temperature by means of a chromium resistor. The two devices are connected in closed-loop through a low noise-low offset electronic circuit. Experimental data, demonstrating the effectiveness of the flow controller, are presented. Limitations of the proposed approach and possible improvements are discussed.

Effect of the Y-piece of the ventilation circuit on ventilation requirements in extremely low birth weight infants

Volutrauma caused by high tidal volumes contributes considerably to the development of bronchopulmonary dysplasia. Yet high tidal volumes are required to overcome dead space. In an experimental arrangement we tested whether reduction of dead space might reduce ventilation requirements and thus reduce volutrauma in preterm infants. The time required to eliminate CO2 by standardized mechanical ventilation from a preterm infant's test lung flooded with CO2 was measured. Four different Y-pieces and flow sensor combinations were tested with and without a device for closed suction: Y-piece without flow sensor; integrated flow sensor; small dead-space flow sensor; and a new dead-space free-flow sensor for preterm infants. CO2 concentrations were measured by a capnograph. Mean CO2 elimination times (+/-SD) were compared. Mean CO2 elimination time was 37.5 s (+/-1.18 s) with and 37.4 s (+/-0.97 s) without closed suction device for the Y-piece without flow sensor, 47.7 s (+/-0.82 s) and 45.5 s (+/-1.18 s) for the integrated flow sensor, 42.5 s (+/-1.27 s) and 41.1 s (+/-0.99 s) for the small dead-space flow sensor and 38.3 s (+/-1.16 s) and 36.8 s (+/-0.79 s) for the dead-space free-flow sensor. CO2 elimination time with and without closed suction device was nearly identical for the Y-piece without flow sensor and for the dead-space free-flow sensor. With both systems, ventilation requirements were significantly lower than for the integrated flow sensor and for the small dead-space flow sensor (integrated flow sensor vs dead-space free-flow sensor 23.6 and 24.5%, respectively, small dead-space flow sensor vs dead-space free flow sensor 11.7 and 10.9%, respectively); thus, we think that introduction of the innovative dead-space free-flow sensor into clinical practice might reduce incidence and severity of bronchopulmonary dysplasia by reduction of volutrauma.

Sensitivity improvement of integrated thermal anemometers obtained by jet flow impingement

A typical integrated hot wire flow sensor, fabricated by means of micromachining, has been characterized in order to evaluate the low flow detection capabilities. The lowest detectable flow has been related to a sensitivity threshold, due to the forced to free convection transition. A simple lumped element model have been used to show the dependence of the sensitivity threshold on the sensor dimensions and the physical parameters of the gas. The resort to the high heat transfer coefficients of fluid jets has been presented as a valid method to improve the sensitivity of the devices. Measurements of the sensor response for various jet diameters and incidence angles have been reported and discussed.

Integrated flow sensor for in situ measurement and control of acoustic streaming in flexural plate wave micropumps

This paper presents the design, fabrication, and characterization of a micromachined flow sensor, which is integrated onto the flexural plate wave (FPW) micropump. The flow sensor and the FPW micropump represent a complex microfluidic system that is able to control the fluid flow in the device. The system was designed using a commercial software package. The microfluidic system of a size of 10×10 mm was fabricated using common fabrication techniques. The micropump is made of an aluminum, piezoelectric zinc oxide, polysilicon, and low-stress silicon nitride membrane with a typical thickness of 1–3 μm. The thermal flow sensor consists of a polysilicon heater and polysilicon–aluminum thermopiles as temperature sensors. The cold junctions of the thermopiles are located in a new design that will avoid the drift effect of the flow sensor. The results show expected flow velocity–drive voltage characteristics.