Micropump with piezoelectric plastic

Harris KhanEvan Leingang

Kevin McLennan

BMEn 5910: Introduction to BioMEMS

Dr. Saliterman

Project Goal

• Polymeric Piezoelectric Materials in Fluid Pumping

• Currently Fabricated but with Ceramic

• Polymer Advantages

Easier and Cheaper Manufacturing

Larger Strains and Displacements

Increased Biocompatibility

Presentation Overview

• Future Prospects of IDDS

• Current Drug Delivery Methods

• Design Challenges of IDDS

• Overview of Polymer Piezo Pump

Fabrication Techniques, Analysis, Testing

• Other Potential Applications for a Plastic Piezo Pump

Conventional Drug Delivery MethodsType Advantages Disadvantages

Oral · Convenient· Simple to administer · Compact· Cheap· Painless

·May cause nausea, stomach irritation and bleeding

·Patients sometimes forget to repeat doses

Injectable · Fast· Effective

· Unpleasant· Painful· Can leave scars

Respiratory/NasalDelivery

· Maximum Surface Area· Only required chemical enters body· Lower Doses· More Economical

· Unpleasant

· Painful

Topical ·Applied straight to region · Difficult & Messy application· Unpleasant odors· Feelings of Greasiness· Tendency to smudge/wear off

Ocular or Otic ·Delivered straight to point of necessity · Blurring of vision· Discomfort· Hard to administer to young children

Implantable Drug Delivery Systems

• Safe

• Effective

• Reliable

• Categories:

Biodegradable/Nonbiodegradable Implants

Implantable Pump Systems

Newest Atypical Class of Implants (Intraocular, Transurethral, etc…)

Design Challenges of IDDS• Disadvantages:

Cost:Benefit Ratio too High

Therefore Restricts their Use over Conventional Dosage Forms

More Complicated Manufacturing Technology

Regulatory Concerns

Polymer Piezo Pump Polymer Piezo Pump –– Design RequirementsDesign Requirements

• Variable flow rates

Programming

• Delivery accuracy

• Reservoir must be easily filled from outside body

• Minimum life of 2 to 5 years before replacement

• Biocompatible with Drug / No toxicity or carcinogenicity in body

• Leak proof

• Must permit wireless communication

DiagnosticsBattery Status

• Must Be Failsafe – Alarms and Notification of Failure

• Inexpensive

• Goal: Design Implantable drug delivery pump utilizing predominately plastic components

Polymer Piezo Pump Polymer Piezo Pump –– Theory of OperationTheory of Operation

• Actuating material: piezo polymer (PVDF) film

• Valveless

• Reservoir – refillable via external port

• On-board battery/power supply

• Wireless communication to a PDA, cell phone or other electronic device

• Approximate size of pumping system: 10 mm x 15 mm

• Stroke volume ~ 150 nL

• Delivery rate range: 0.1 – 100 µL

Polymer Piezo PumpPolymer Piezo Pump

Bohm, et al. 1999

Xia, et al. 2005

Polymer Piezo Pump Polymer Piezo Pump –– AdvantagesAdvantages

• Other methods of implantable drug delivery involve complex electro-mechanical systems potential for electrical or mechanical failure is high

• Ceramic piezos are brittle, which limits their fracture resistance and deformation

Polymers are elastic and can absorb large amounts of impact energy

A piezo pump has few moving parts that can fail, minimal design complexity, and piezo actuators are extremely reliable

Piezo pumps do not require manufacturing tolerances to be held astightly as in mechanically-driven pumps

Large strains are possible with polymers less power is required to generate equivalent amounts of strain when compared with ceramics

Design AdvantagesDesign Advantages

• Polymer material is relatively inexpensive compared to silicon

Conventional plastic manufacturing processes like injection molding may be implemented to form these parts• Extremely high tolerances can be met• Very small dimensions can be achieved• Inexpensive• Easily scalable to mass production

• Ceramic-based MEMS must be fabricated using expensive clean-room technology borrowed from IC industry

Polymer Piezo Pump Polymer Piezo Pump –– AdvantagesAdvantagesDesign AdvantagesDesign Advantages

• Properties of polymers can be readily changed by additives

• Polymer devices are radiolucent in x-rays, safe in MRIs, and do not produce artifacts in CT films

• Many types of polymers are sterilizable

Manufacturing AdvantagesManufacturing Advantages

Limitations of the TechnologyLimitations of the Technology

Carcinogenicity / ToxicityThere is the potential for certain polymers to have negative interactions with the body significant testing would be required

Miniaturization comes at a costLower force output of polymer piezo when compared to ceramic piezoPiezo actuation forces are proportional to the area of the piezo material

Power requirementsHigh voltages are required to achieve piezoelectric behavior, especially in PVDF filmsSignificant advances in electrical engineering / battery technology might be necessary to realize this device

• In addition to the design and manufacturing challenges faced by all bioMEMS devices, there are specific hurdles related to plastic piezo technology that would need to be addressed

Polyurethane, polyethylene, and PEEK have all been successfully implanted for long-term applications

Conductive polymers are being researched for use as wiring, circuit board components and “all plastic” electronics

• Replacement of electronic components with plastic

• Implantability of polymers in the human body

Current Research AreasCurrent Research Areas

Large strains are possible when the material is mechanically stressed

• Piezo films need to be manufactured in such a way that:

• Application of a high electric field may be utilized during processing to increase alignment

FabricationFabricationProduction of PVDF FilmProduction of PVDF Film

A high density of permanent molecular dipoles are present

The molecular dipoles are oriented or aligned to achieve the disiredpiezoelectric response

The dipole alignment can be sustained once it is achieved

• Standard plastic film extrusion techniques may be employed to produce the PVDF film

• The film must be mechanically stretched to align the piezoelectric domains

• Micro hot embossing may be utilized to form individual PVDF piezo actuator parts

• Polymer bond fusion technology to bond plastic housing together

FabricationFabricationFabrication of Individual Piezo Actuators Fabrication of Individual Piezo Actuators

From the Extruded FilmFrom the Extruded Film

• Stereolithography

Fu, 2004

• Conventional injection molding, micro molding, or stereolithography may be used to fabricate the other plastic components

• Polymer bond fusion technology could be utilized to bond materials together

FabricationFabricationProduction of Housing Parts Production of Housing Parts

Assembly of ComponentsAssembly of Components

Santa Clara University 1998

Piezoelectric Polymer Applications

• Medical• Actuators• Sensors• Industrial• Space

Medical Applications – Drug Delivery

• Diabetes management▫ Open loop insulin delivery

• Direct brain infusion of neurotransmitters▫ Parkinson, balance dopamine deficiency▫ Alzheimer, help slow or lessen effects

• Spasticity caused by spinal cord injuries or multiple sclerosis▫ Oral drugs may cause drowsiness, confusion and

weakness. Intrathecally delivered drugs via bioMEMS devices can eliminate these effects

Medical Applications Medical Applications -- CancerCancer• Chemotherapy

▫ Implantable pump permits timed delivery▫ Timed treatments during Circadian cycle

more effectiveless toxiccause fewer side effects

• Pain management▫ Intrathecally delivered morphine sulfate

Successful where oral medications failed

Medical Applications - Analysis• µTAS (Micro Total Analysis System)

▫ Micropumps move fluids throughout chip ▫ Sensors utilizing piezo polymers

• LOC (Lab on a Chip)▫ Defense interests include biological and chemical

detection▫ Portable field analysis equipment

• Genomics arrays▫ Human Genome Project-improving DNA analysis

Piezoelectric motors• Advantages

▫ power efficiency▫ torque/mass ratios▫ compact size▫ efficient self holding force▫ MRI safe▫ High frequencies (up to 5 MHz)

• Applications▫ Camera auto focus lenses▫ Watch motors▫ Compact paper handling

• Audio equipment▫ Loudspeakers, microphones

Ultrasonic piezoelectric motor

Piezoelectric sensors

• Diesel engines▫ Clamp on pressure transducers▫ Fuel injectors

• Aircraft design and manufacturing▫ Shock wave and impact sensors▫ Less stringent preparation-not affect by prior loading

• Vibration reduction▫ When the material is bent by a vibration in one direction,

the system observes the bend and sends electric power to the piezo element to bend in the other direction.

Similar to noise reduction headphones

PVDF Stress Sensor

Robotic Applications• Robotic grip

▫ Piezo sensors respond to changes in temperature, pressure and strain

▫ Prevent slipping and improve overall grip performance

▫ Eliminates overshoot of target force

Space Applications• High reliability low power pumps for fluid management during

planetary missions -automated chemical processes

• Circulation pump for fluids in water storage system to prevent bacteria growth on walls

• General actuator for a variety of space applications including automation and robotic

• Materials International Space Station Experiment (MISSE-6) ▫ Piezoelectric polymer films

launched into low Earth orbit

▫ Ultra light mirrors in space telescopes

ReferencesReferencesRanade, VV: Drug delivery systems. 4. Implants in drug delivery. The Journal of Clinical Pharmacology, 1990:30:871 Harrison

Fu Y, Harvey EC, Ghantasala MK, Spinks G. "Design, modeling and fabrication of piezoelectric polymer actuators", Proceedings of the SPIE, Vol. 5276, pp. 113-118, 2004

Maillefer D, van Lintel H, Rey-Mermet G, Hirschi R. "A high-performance silicon micropump for an implantable drug delivery system", The 14th IEEE International Conference on Micro Electro Mechanical Systems, pp. 413-417, 2001

Xia F, Tadigadapa S, Zhang QM. "Electroactive polymer based microfluidic pump", Sensors and Actuators A, 125, 346-352, 2006

Junwu K, Zhigana Y, Taijiang P, Guangming C, Boda W. "Design and test of a high-performance piezoelectric micropump for drug delivery", Sensors and Actuators A, 121, 156-161, 2005

Santa Clara University Design Center. The Injection Molding Machine. 1998 Santa Clara University. 24 April 2007. <http://www.scudc.scu.edu/cmdoc/dg_doc/develop/process/control/b1000001.htm>

Questions?