Frequency-controlled wireless passive microfluidic devices

Microfluidics is a promising technology that is increasingly attracting the attention of researchers due to its high efficiency and low-cost features. Micropumps, micromixers, and microvalves have been widely applied in various biomedical applications due to their compact size and precise dosage controllability. Nevertheless, despite the vast amount of research reported in this research area, the ability to implement these devices in portable and implantable applications is still limited. To date, such devices are constricted to the use of wires, or on-board power supplies, such as batteries. This thesis presents novel techniques that allow wireless control of passive microfluidic devices using an external radiofrequency magnetic field utilizing thermopneumatic principle. Three microfluidic devices are designed and developed to perform within the range of implantable drug-delivery devices. To demonstrate the wireless control of microfluidic devices, a wireless implantable thermopneumatic micropump is presented. Thermopneumatic pumping with a maximum flow rate of 2.86 μL/min is realized using a planar wirelessly-controlled passive inductor-capacitor heater. Then, this principle was extended in order to demonstrate the selective wireless control of multiple passive heaters. A passive wirelessly-controlled thermopneumatic zigzag micromixer is developed as a mean of a multiple drug delivery device. A maximum mixing efficiency of 96.1% is achieved by selectively activating two passive wireless planar inductor-capacitor heaters that have different resonant frequency values. To eliminate the heat associated with aforementioned wireless devices, a wireless piezoelectric normally-closed microvalve for drug delivery applications is developed. A piezoelectric diaphragm is operated wirelessly using the wireless power that is transferred from an external magnetic field. Valving is achieved with a percentage error as low as 3.11% in a 3 days long-term functionality test. The developed devices present a promising implementation of the reported wireless actuation principles in various portable and implantable biomedical applications, such as drug delivery, analytical assays, and cell lysis devices

Modeling and simulation of a wirelessly-powered thermopneumatic micropump for drug delivery applications

This paper presents modeling and finite element analysis of a thermopneumatic micropump with a novel design that does not affect the temperature of the working fluid. The micropump is operated by activating a passive wireless heater using wireless power transfer when the magnetic field is tuned to match the resonant frequency of the heater. The heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element. The solution inside the reservoir is pumped through a microchannel that ends with an outlet hole. The thermal and pumping performances of the micropump are analyzed using finite element method over a low range of Reynold’s number ⩽ 10 that is suitable for various biomedical applications. The results demonstrate promising performance with a maximum flow rate of ∼2.86 μL/min at a chamber temperature of 42.5 ºC, and a maximum pumping pressure of 406.5 Pa. The results show that the developed device can be potentially implemented in various biomedical areas, such as implantable drug delivery applications

Metamodel-based Optimization of a PID Controller Parameters for a Coupled-tank System

Liquid flow and level control are essential requirements in various industries, such as paper manufacturing, petrochemical industries, waste management, and others. Controlling the liquids flow and levels in such industries is challenging due to the existence of nonlinearity and modeling uncertainties of the plants. This paper presents a method to control the liquid level in a second tank of a coupled-tank plant through variable manipulation of a water pump in the first tank. The optimum controller parameters of this plant are calculated using radial basis function neural network metamodel. A time-varying nonlinear dynamic model is developed and the corresponding linearized perturbation models are derived from the nonlinear model. The performance of the developed optimized controller using metamodeling is compared with the original large space design. In addition, linearized perturbation models are derived from the nonlinear dynamic model with time-varying parameters

Finite element analysis of material removal rate for Si wafer using heat-assisted µEDM

Micro-electrical discharge machining (µEDM) has been proved to produce high surface quality results in Si machining. In previous studies, the researchers reported the Si machining using the µEDM with several strategies such as plating, doping and temporary coating process to be machined by the µEDM. This paper reports a numerical simulation of MRR performance results using COMSOL Multiphysics. The effects of the machining temperature in Si machining using heat-assisted µEDM on achieving the optimum MRR results is studied. The simulation results showed the highest MRR is 1.48666 × 10-5 mm3/seconds achieved at 250 °C

Development of 4D printed PLA actuators

Four-dimensional (4D) printing is currently in the early stages of development and is deficient in offering designers and researchers the freedom to develop 4D printable structures. The first step to ensuring the use of such technology by researchers requires additional testing and simulation for 4D printing. It also requires an assessment of the shape memory effect in the materials that are being printed. This paper tests 4D printed actuators that possess an induced strain following printing. The induced strain is achieved during the printing process following fused deposition modelling. The induced strain permits alteration of the shape after material stimulation following printing, which eliminates the requirement for a separate programming step where alterations are required for force and stimulation to achieve the print shape temporarily. The proposed approach consists of two actuators and a drug delivery application via an open-sided box reservoir. The process of printing and shape change of polylactic acid is completed and the level of bending of actuators is then measured. The printing of designs is done at 10 mm/s for passive layers and 60 mm/s speed for active layers. The heating of the printed samples is done, and the bending angle is measured for the replication process through simulation. Finite element analysis (FEA) of the actuators is done to replicate the strain-induced through the use of materials demonstrating thermal expansion. The FEA parameters are utilized to develop intricate structures and simulate the change of the shape. The deformation values achieved by Designs 1 and 2 in the z-axis are 7.81 mm and 6.06 mm, respectively, and 4.84 mm for the reservoir

Geometrical analysis of diffuser-nozzle elements for valveless micropumps

This paper reports a geometrical analysis and tuning-approach for diffuser-nozzle elements for valveless micropumps. Finite element analysis studies are performed in order to investigate the impact of the angle, curvature ratio, and length of the diffuser on the pumping efficiency. Parametric sweep studies are implemented at Reynolds number (Re) values ranging from 10 to 100 while observing the pressure coefficients in the nozzle and diffuser directions, as well as the flow separation and the resultant efficiency of the diffuser. The results suggest that a diffuser with an angle of 10° and a curvature ratio of 0.4 possesses the highest efficiency among the other diffusers within the Re range of this study. In addition, it is observed that the length of the diffuser has a positive effect on the efficiency, where the length is usually restricted by the overall size of the device. The results provide comprehensive designing guidelines for diffusers elements that can be used in microfluidic devices for various biomedical applications

Wireless powered thermo-pneumatic micropump using frequency-controlled heater

This paper reports a novel, wirelessly powered micropump based on thermo-pneumatic actuation using a frequency-controlled heater. The micropump operates wirelessly through the energy transfer to a frequency-dependent heater, which was placed underneath the heating chamber of the pump. Heat is generated at the wireless heater when the external magnetic field is tuned to the resonant frequency of the heater. The enclosed air in the chamber expands and forces the liquid to flow out from the reservoir. The developed device is able to pump a total volume of 4 ml in a single stroke when the external field frequency is tuned to the resonant frequency of the heater at the output power of 0.22 W. Multiple strokes pumping are feasible to be performed with the volume variation of ~2.8% between each stroke. Flow rate performance of the micropump ranges from 1.01 µL/min to 5.24 µL/min by manipulating the heating power from 0.07 W to 0.89 W. In addition, numerical simulation was performed to study the influence of the heat transfer to the sample liquid. The presented micropump exclusively offers a promising solution in biomedical implantation devices due to its remotely powered functionality, free from bubble trapping and biocompatible feature

Techno‐economic analysis of direct combustion and gasification systems for off‐grid energy supply: A case for organic rankine cycle and dual fluidized‐bed

Biomass is one of the most versatile sustainable energy sources. This versatility allows utilization of different biomass feedstock using a verity of conversion techniques. Often, a biomass-to-bioenergy conversion method is selected depending on the application, end-use product, and the type of feedstock. In many applications such as residential energy supply, it is possible to select amongst various technologies. Although, there exist several challenges such as cost-effectiveness and sustainability that constrains bioenergy development. To this end, this research elaborates on the impacts of different conversion methods on techno-economic performance of bioenergy systems for residential energy supply. In this context, Organic Rankine Cycle based on direct combustion, and Dual Fluidized-Bed technology based on gasification were selected for that purpose. A techno-economic comparative analysis illustrates that the primary product of the system and fuel cost are the two most important factors in feasibility assessment. The negative impact of feedstock price was more severe on the Organic Rankine Cycle. For wood chips prices below 55$/t, Organic Rankine Cycle could be the better option due to lower capital and maintenance costs. In contrast, Dual Fluidized-Bed could better tolerate the variation of feedstock price; offering 8$/t wood chips

Modeling and control of piezoelectric stack actuators with hysteresis

Piezoelectric actuators are popularly applied as actuators in high precision systems due to their small displacement resolution, fast response and simple construction. However, the hysteresis nonlinear behavior limits the dynamic modeling and tracking control of piezoelectric actuators. This thesis studies a dynamic model of a moving stage driven by piezoelectric stack actuator. The Bouc-Wen model is introduced and analyzed to express the nonlinear hysteresis term of the piezoelectric stack actuator, where the values of the parameters of the model have been taken from a previous work. The simulated results using MATLAB/Simulink demonstrate the existence of the hysteresis phenomenon between the input voltage and the output displacement of the piezoelectric stack actuator, and validate the correctness of the model. Moreover, a Luenberger observer is designed to estimate the hysteresis nonlinearity of the system, and then combined with the voltage input signal to form a Luenberger-based feedforward controller to control the displacement of the system. Furthermore, a Proportional-Integral-Derivative (PID) feedback controller is integrated with the feedforward controller to achieve more accurate output displacement, where the gains of the PID controller are optimized using Particle Swarm Optimization. Several performance index formulas have been studied to get the best solution of the PID’s gains. An Integral Time Squared Error plus Absolute Error performance index formula has been proposed to achieve zero overshoot and steady-state error. The simulated results accomplished using MATLAB/Simulink show the ability of the designed controllers to vastly reduce the amount of error of the output displacement and the response time of the system

A wirelessly-controlled piezoelectric microvalve for regulated drug delivery

This paper reports a novel wireless control of a normally-closed piezoelectric microvalve activated by a wireless inductor-capacitor (LC) resonant circuit, and enabled by an external magnetic field. The LC circuit is formed by connecting a multilayer coil to a piezoelectric actuator (PEA) that behaves as a capacitor and a resistor in parallel. The LC circuit is activated by modulating the field frequency to its resonant frequency (fr) of 10 kHz, which matches the optimal operating frequency of the device, while considering the resonant frequency of the PEA. The working fluid is stored in an 88.9 μL polydimethylsiloxane balloon reservoir that pumps the liquid due to the difference in pressure, which eliminates the need for a pump. The design of the device was optimized using several analytical and experimental approaches. This device was fabricated using a time and cost-effective out-of-clean-room fabrication process. The valving performance was initially characterized in air, then in phosphate buffered saline (PBS) solution to mimic the drug release kinetics into human interstitial body fluids. Maximum flow rate values of 8.91 and 7.42 μL/min are achieved in air and PBS solution respectively, at a maximum input pressure value of ∼13 kPa. A programmed short-term delivery of desired liquid volumes in separate batches shows that the volumes are delivered into air and PBS solution with maximum percentage errors of 7.49% and 7.91%, respectively. Additionally, a programmed 3-day long-term reliability test shows that the device was able to achieve desired flow rate values between 160 and 320 μL/day in air and PBS solution with a maximum percentage error of 3.11% and 4.39%, respectively. The results show that the developed device has high potential to be used in drug delivery applications