Introduction to BioMEMS & Medical Microdevices Drug Delivery Systems Companion lecture to the textbook: Fundamentals of BioMEMS and Medical Microdevices, by Prof., http://saliterman.umn.edu/
Star Tribune February 12, 2012 Image courtesy of MicroCHIPS, photo by Dana Lipp
Classification of Micropumps Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Mechanical Displacement Micropump These use the motion of a solid (such as a gear or diaphragm) or a fluid to generate the pressure difference needed to move fluid. They need a physical actuator for the pumping and they have moving parts. Type include piezoelectric, electrostatic, thermo pneumatic, electromagnetic, bimetallic, Ion Conductive Polymer Films (ICPF)and Shape Memory Alloy (SMA). Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Mechanical Displacement Micropump Tsai, NC and CY Sue. Review of MEMS-based drug delivery and dosing systems. Sensors and Actuators A 134 (2007) 555-564
What are the Left Heart Analogies? Actuator? Inlet Chamber? Inlet Valve? Main Chamber? Outlet Valve? Outlet Vessel?
Answers Actuator: Smooth Muscle Inlet Chamber: Left Atrium Inlet Valve: Mitral Valve Main Chamber: Left Ventricle Outlet Valve: Aortic Valve Outlet Vessel: Aorta
Electrostatic Micropump These use electrostatic forces in their actuation mechanism. The pressure difference induced by the membrane deflection in the pump chamber forces fluid in the reservoir to flow in the microchannels. The electrostatic force is defined as the electrical force of attraction and repulsion induced by an electric field where like charges repel, unlike charges attract. Electrostatic actuator has only a small stroke and the deflection of the diaphragm can be easily controlled by the applied voltage. Low power consumption and fast response. Well suited for peristaltic pumping. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Electrostatic Micropump Tsai, NC and CY Sue. Review of MEMS-based drug delivery and dosing systems. Sensors and Actuators A 134 (2007) 555-564
Peristaltic Pumping Action Patrascu, M., et al. Flexible, electrostatic microfluidic based on thin film fabrication. Sensors and Actuators A 186(2012) 249-256
Piezoelectric Micropump Piezoelectric mechanism finds common use in the reciprocating micropumps of drug delivery and other biomedical applications. Main advantages of piezoelectric actuators include large actuation force, fast response and simple structure. Fabrication is complex as is processing of piezoelectric materials. Disadvantage of the comparatively high actuation voltage and small stroke volume. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Implantable Microport System Concept of an active microport Geipel, A., et al. 2008. Design of an implantable active microport system for patient specific drug release. Biomedical Microdevices 10, no. 4:469-478.
The Piezoelectric Pump Schematic cross section of the piezoelectric micropump with a close-up of the valve geometry Three-phase actuation scheme of the micropump Geipel, A., et al. 2008. Design of an implantable active microport system for patient specific drug release. Biomedical Microdevices 10, no. 4:469-478.
Micropump Chip Photograph of the two membrane silicon micropump chip (a) and REM-picture of the valve lip (b). Geipel, A., et al. 2008. Design of an implantable active microport system for patient specific drug release. Biomedical Microdevices 10, no. 4:469-478.
Active Microport Design & Prototype (a) Cross-sectional drawing of the active microport design visualizing the embedded fluidic elements, and the integration of a silicon micropump chip and a pressure sensor. (b) Photograph of a prototype of the active microport system. Geipel, A., et al. 2008. Design of an implantable active microport system for patient specific drug release. Biomedical Microdevices 10, no. 4:469-478.
Thermopneumatic Micropump A chamber full of air is periodically and alternately expanded and compressed by a pair of heater and cooler. The periodic change in the volume of the chamber gives the membrane a regular momentum so fluid can flow out. This type generates relatively large induced pressure and membrane displacement. Two disadvantages are the need for the driving power to be maintained at a constant and specific level and the slow response. The thermo-pneumatic actuation has a thermally induced volume change and/or phase change of fluids sealed in a cavity with at least one compliant wall Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Thermopneumatic Pump Tsai, NC and CY Sue. Review of MEMS-based drug delivery and dosing systems. Sensors and Actuators A 134 (2007) 555-564
Shape Memory Alloy Micropump SMAs are metals that show two unique properties such as pseudo elasticity and Shape Memory (SM). The diaphragm of SMA micropumps is made mostly of Titanium/Nickel alloy (TiNi) Transformation between two solid phases: the austenite phase (at high temperatures) and the marten-site phase (at low temperatures). Considerable forces are generated if subjected to mechanical constraint while returning to the predeformed shape. High force-to-volume ratio, ability to recover large transformation stress and strain upon heating and cooling processes, high damping capacity, chemical resistance and biocompatibility. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
SMA Micropump Tsai, NC and CY Sue. Review of MEMS-based drug delivery and dosing systems. Sensors and Actuators A 134 (2007) 555-564
Bimetallic Micropump Bimetallic actuation functions differently on different Coefficients of Thermal Expansion (CTE) of materials. The diaphragm of bimetallic micropump is made of two different metals having different CTEs. Bonding mechanism of dissimilar materials and their subjection to temperature changes induce thermal stresses because the coefficients of the metals differ, providing a means for actuation. The implementation extremely simple with large forces generated but the deflection of a diaphragm is only can be achieved by thermal alternation. The key advantage is that bimetallic micropumps require relatively low voltages than the other types of micropumps. Their main disadvantage is their unsuitability to high-frequency operation. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Bimetallic Micropump Tsai, NC and CY Sue. Review of MEMS-based drug delivery and dosing systems. Sensors and Actuators A 134 (2007) 555-564
Ionic-Conductive Micropump Polymer MEMS actuators that can be actuated in aqueous environments with large deflection. They are actuated by stress gradient from the ionic movement due to an electric field. Composed of polyelectrolyte film with both sides chemically plated with platinum. The two films have high electrical conductivity. One diaphragm-end is fixed. An ICPF diaphragm can be controlled by bending it upside or downside in certain value of voltages applied to the electrodes within a certain duration. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Ionic-Conductive Micropump Continued The presence of an electric field causes the ions in both sides of the polymer molecule chain to move to the cathode. Simultaneously, each ion with a positive charge will take some water molecules and move towards the cathode. The ionic movement causes the cathode to expand and the anode to shrink. The presence of an alternating voltage signal will bend the films alternately. ICPF actuators have advantages such as low driving voltage, quick response and biocompatibility. They can work in aqueous environments. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Ionic-Conductive Polymer Film Tsai, NC and CY Sue. Review of MEMS-based drug delivery and dosing systems. Sensors and Actuators A 134 (2007) 555-564
Non-Mechanical Pumps Electrokinetic micropumps often use an electric field to pull ions within the pumping channel, in turn dragging along the bulk fluid by momentum transfer due to viscosity. Magneto kinetic micropumps typically use Lorentz force on the bulk fluid to drive microchannel flow. Dynamic pumps do not usually have valves; they obtain directionality from the direction of the applied force. Li, Tao et al.. Compact, power-efficient architecture using microvalves and microsensors for intrathecal, insulin, and other drug delivery systems. Advanced Drug Delivery Reviews 64 (2012) 1639-1649
Electrokinetic Microfluidic Pump (a) Schematic representative section of an electroactive microwell drug delivery system. Inset: cross sectional view. (b) Fabricated and assembled device with electrical leads connected to thin copper wires. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
System Operation System operation. (a) Stage 1: to electrochemically dissolve the membrane a potential is applied between the two upper electrodes. (b) Stage 2: after dissolution to eject the contents, the potentials applied between the upper electrode and the lower one on the PDMS. (c) Magnified view of microchip from above looking at the region near the membrane. Pale yellow regions (membrane and C-shape gold features) are gold where the polyimide layer was etched. (d) An example of gold PDMS bottom substrate. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Ejection from the Microwells Time lapse illustrating repulsion the ejection of 1.9 mm fluorescent polystyrene microsphere particles from an electroactive microwell. (a) After dissolution of the membrane, the fluorescent particles can be seen in the well. White lines outline the gold electrodes features. (b) (f) frames taken every 2 s (total of 10 s) after application of a 4.0 V potential. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Video of Ejection Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Dispersion & Front Velocity (a) Dispersion radius vs. time for different applied potentials. (b) Instantaneous front velocity as a function of time. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Time to Empty & Power Load Time required to completely empty the contents of the microwell as a function of applied potential. (a) Average power load during ejection process. (b) Total energy consumed to completely empty the well using the times above. The line through the data points in this Figure represents a quadratic best fit. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Electric Fields & Streamlines Computed electric field lines in electroactive microwell. Finite element simulations of the transport process. (a) Transport streamlines for pure electroosmosis. (b) Streamlines when all electrokinetic effects are considered. Color contours show applied potential ranging from blue (ground) to red (maximum potential). Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Video of Recirculation of Flow Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Time-Dependent Species Transport Finite element analysis of time-dependent species transport. Images show cut view of species concentration every 5 s up to 25 s after the ejection process (a) electroosmosis only (b) electrophoresis and electroosmosis. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Radius vs Time Results Plot comparing experimental and numerical results on the 3.5 V case. Aram J. Chung, Donn Kim, and David Erickson. 2008. Electrokinetic microfluidic devices for rapid, low power drug delivery in autonomous microsystems. Lab on a Chip - Miniaturization for Chemistry & Biology 8, no. 2:330-338.
Other Non-Mechanical Micropumps Magneto Hydro Dynamic (MHD) Micropumps. Electro Hydrodynamic Micropumps (EHD). Electro-Osmotic Micropumps (EO) DC Electro-Osmotic (DCEO) Micropumps. AC Electro-osmotic (ACEO) Micropumps. Electrowetting (EW) Micropumps. Bubble-type Micropumps. Electrochemical Micropumps
Microneedles & Transdermal Delivery Geipel, A., et al. 2008. Design of an implantable active microport system for patient specific drug release. Biomedical Microdevices 10, no. 4:469-478.
Opening Schemes Roxhed, Niclas, Patrick Griss, and Goran Stemme. 2008. Membrane-sealed hollow microneedles and related administration schemes for transdermal drug delivery. Biomedical Microdevices 10, no. 2:271-279.
Fabrication Roxhed, Niclas, Patrick Griss, and Goran Stemme. 2008. Membrane-sealed hollow microneedles and related administration schemes for transdermal drug delivery. Biomedical Microdevices 10, no. 2:271-279.
Membrane Bursting Pressure Roxhed, Niclas, Patrick Griss, and Goran Stemme. 2008. Membrane-sealed hollow microneedles and related administration schemes for transdermal drug delivery. Biomedical Microdevices 10, no. 2:271-279.
Pre & Post Gold Membrane Removal Roxhed, Niclas, Patrick Griss, and Goran Stemme. 2008. Membrane-sealed hollow microneedles and related administration schemes for transdermal drug delivery. Biomedical Microdevices 10, no. 2:271-279.
Post Insertion & Evaporation Test Roxhed, Niclas, Patrick Griss, and Goran Stemme. 2008. Membrane-sealed hollow microneedles and related administration schemes for transdermal drug delivery. Biomedical Microdevices 10, no. 2:271-279.
Summary Chip Reservoir Drug Delivery Systems. Mechanical Displacement Pumping. Electrostatic Piezoelectric Thermopneumatic Shape Memory Alloy Bimetallic Ion Conductive Non-Mechanical Micropumps. Electrokinetic Microneedles.