Design, analysis and fabrication of MEMS based microfluidic devices for drug delivery systems | |
| Author | Nisar, Asim |
| Call Number | AIT Diss. no.ISE-08-05 |
| Subject(s) | Microelectromechanical systems Drug delivery systems |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Design and Manufacturing Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ISE-08-05 |
| Abstract | Microelectromechanical Systems (MEMS) is a rapidly growing field which enables the manufacture of small devices using micro fabrication techniques similar to the ones that are used to create integrated circuits. In the last two decades, MEMS technologies have been applied to the needs of biomedical industry giving rise to a new emerging field called Microfluidics. Microfluidics deals with design and development of miniature devices which can pump, monitor and control small volumes of fluids. An integrated MEMS based transdermal drug delivery system (DDS) consists of drug reservoir, micropumps, valves, microsensors, microchannels, microneedles and necessary related circuits. A typical micropump is a MEMS device, which provides the actuation source to transfer the fluid (drug) from the drug reservoir to the body (tissue or blood vessel) with precision, accuracy and reliability. Microneedles provide an interface between the drug delivery system and the patients' body for releasing the drug. The use of microneedles is advantageous by eliminating pain and inconvenient intravenous injections. Micropumps and microneedles are therefore essential components in transdermal drug delivery systems. A number of micropump based drug delivery systems for chemotherapy for cancer patients, insulin delivery for diabetic patients and so on have been developed. However, the commercialization of micropump based transdermal drug delivery systems for biomedical application such as treatment of cardiovascular or hemodynamic disorders is still in its infancy. Although a lot of technical information is available for a number of design concepts for micropump based drug delivery systems, however, little focus has been paid to design and analysis of the drug delivery systems and its components. Furthermore, many of the novel concepts of micropumps reported in literature for drug delivery and other biomedical applications still need to be incorporated into practical and commercially viable devices. The scope of this thesis covers analysis, fabrication and characterization of piezoelectrically actuated valveless micropumps and process development and fabrication of hollow microneedles for transdermal drug delivery system for cardiovascular disorders such as treatment of hypertension. Because of the complexity in analysis of piezoelectric micropump, which involves structural and fluid field couplings in a complicated geometrical arrangement, finite element (FE) numerical simulation rather than an analytical system has been used. The behavior of the piezoelectric actuator with biocompatible polydimethylsiloxane membrane has been first studied by conducting piezoelectric analysis. Then the performance of the valveless micropump has been analyzed by building a three dimensional electric-solid-fluid model of the micropump. The effect of geometrical dimensions on micropump characteristics and efficiency of nozzle/diffuser elements of a valveless micropump have been investigated in the transient analysis using multiple code coupling method. The deformation results of the membrane using multifield code coupling analysis are in good agreement with analytical as well as results of single code coupling analysis of a piezoelectric micropump. The analysis predicts that to enhance the performance of the micropump, diffuser geometrical dimensions such as diffuser length, diffuser neck width and diffuser angle need to be optimized. Micropump flow rate is not strongly affected at low excitation frequencies trom 10 to 200 Hz. The itation voltage is the more dominant factor that affects the flow rate of the micropump as compared with the excitation frequency. However, at extremely h excitation frequencies beyond 8 kHz, the flow rate drops as the membrane libits multiple bending peaks which is not desirable for fluid flow. The set of ltifield simulations in the analysis have provided a valuable benchmark and diction data as it allows transient, three dimensional, sequential piezoelectric and fluid analysis of the micropump, thereby facilitating a more realistic Itifield analysis. Following the extensive numerical analysis, actual fabrication and performance characterization of the micropump has been presented. The performance of the micropump has been characterized for different micropump chamber diameters for potential applications in drug delivery systems. The experimental results of piezoelectric disc/ membrane deflection and micropump flow rates at varying voltage and excitation frequency have been presented. Finally a process for fabricating hollow silicon out of plane microneedle arrays been developed for transdermal drug delivery applications. The inner hollow hole and the fluidic reservoir have been fabricated in deep reactive ion etching process. The profile of outside needles has been achieved by combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of isotropic etching and Bosch process, the high aspect ratio and high density microneedle arrays have been fabricated successfully for transdermal drug delivery system |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ISE-08-05 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Industrial Systems Engineering (ISE) |
| Chairperson(s) | Afzulpurkar, Nitin ;Banchong Mahaisavariya (Banchong Mahaisavariya,|eCo-Chairperson); |
| Examination Committee(s) | Adisorn Tuantranont ;Bohez, Erik, L.J. ; |
| Scholarship Donor(s) | Higher Education Commission,(HEC),Pakistan ;Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2008 |