disposable drug delivery system

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Disposable Drug

Delivery SystemRoss Gerber, Aman GhotraKarim Mahamud, & Prakash Rao

Client: Michael MacDonald, MDDept. of Pediatrics UW Hospital & Clinics

Adv isor : William Murphy, PhDDept. of Biomedical Engineering


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O utline

BackgroundInsulin, Type I diabetes, drug delivering devices

Problem StatementDesign Constraints, Motivation

Proposed Design Solutions : Reaction PumpMicrofluidic Pump

Motor Driven PumpEvaluation

Future Work


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BackgroundInsulinProduced in Pancreas

Essential protein for glucoseregulationLow insulin levels can lead to

coma or deathType I Diabetes Autoimmune Disease that stopsinsulin production

Affects children and youngadultsPatients must inject insulinperiodically


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Background (cont.)

Current InsulinDelivering Devices :

Syringes

Insulin PensInsulin jet injectorsInsulin pumps

Have a small reservoir,syringe, programmablehand padCommonly used by TypeI diabetics


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Problem Statement

Develop a small, automatic,inexpensive (and possibly disposable)

drug delivery system that can give acontinuous flow of a protein-baseddrug over period of twenty-four hours.


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Design Constraints

A new insulin drug pump must :Deliver solutions at a constant rate for over aperiod of 8-24 hours at 10-100 L/hr Hold up to 0.5 ml of total solutionNot be bulky or heavyBe cost-efficient (maximum cost : $1000.00)

Be user friendlyBe easily sterilized


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Motivation

Current insulin pump users are dissatisfied,as they :

Do not provide constant flow rates Are expensive ($5,000-7,500)


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Design 1 : Reaction Pump

Spring generates force As solid organiccompound dissolves,spring is allowed to workReaction is initiatedwhen glass membrane isbrokenRate of reactiondetermines the rate of delivery


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Progress of Dissolution

Compoundsbefore reaction

t=0

Compounds atbeginning of

reaction

t=1hr

Compoundsnear end of

reaction

t=8hr

View of diffusion

grate


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Reaction Pump : Components

Spring (1)Liquid Reactant (2)

Solid Reactant (3)Plunger and Grate (4)Insulin (5)Chamber (6)

Start Pin (7)


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Reaction Pump : Mechanism

Button (7) is pushed tobrake thin membrane (9)Water layer (2) is exposedto dissolvable organiccompound (3)

As the compound dissolves,it passes through the grate(9) at the top of the plunger (4)

Allows plunger (4) to move

down to push insulin (5) outof chamber (6) into therecipient


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Reaction Pump : Evaluation

AdvantagesVery smallConstant rate

DisposableNo electronicsEasy to useCan vary amount of insulin delivered byconcentration

DisadvantagesMust determine chemicalreaction

No feedback mechanismInsulin can possibly beforced in if an externalforce is appliedCould fall off


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Microfluidic System

ComponentsMicro-pump

Reciprocating Displacement type

Passive micro-valveControl Circuit

Can precise and controllable amount of fluid

in the range of L/min mL/min


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Reciprocating Micropump O peration

Moving surface doespressure work on workingfluid in periodic manner

Force-applying movingsurface deformable plate(pump diaphragm)

Basic components pumpchamber (on 1 side of pumpdiaphragm), actuator mechanism, and 2 passivecheck valves


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Piezoelectric Actuator MechanismPiezoelectric Excitation

If material subjected tomechanical tension,electrical polarizationproportional to extensionwould occur

O pposite also holds true,where material deformationoccurs as a result of applied electric field(inverse piezoelectriceffect)

PZT, Zn OCan be used to benddiaphragm


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Piezoelectric Actuator Mechanism (cont.)

O perationDriver acts on diaphragm to alternate increase & decrease of pump

chamber volumeFluid drawn into pump chamber during fluid intake stroke (diaphragmexpands), and force out during discharge stroke (diaphragm contracts)Check valves @ inlet and outlet favor bidirectional flow, therebyrectifying the flow over a two-stroke pump cycle


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Evaluation - Microfluidic Pump

Adva nt ag es

Very small Accurate deliveryWould essentially actas an artificial pancreas

D is adva nt ag es

Too expensive for disposable use

Closed loop feedbackcontrol with glucosesensor is still yearsaway

Very difficult tofabricate


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Design 3 : Motor Driven Pump

Components :SyringeTubing

Programmable Electronic CircuitPC can change flow rates

A circuit is responsible for converting step and directionsignals into winding energized patterns

Stepping motor Rotates counter-clockwise and clockwiseVariable steps (, , etc.)Smaller steps provide more torque


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Motor Driven Pump

Components (cont)Converter :

Converts rotationalmotion into linear motionDrives the syringe whichdelivers insulin


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Evaluation : Motor Driven Pump

AdvantagesInexpensive ($350)Small

SizeEasy to sterilizeProvides constant rate

DisadvantagesNot waterproof

Bathing, swimming

Not effective during mealtimes


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Decision Matrix

R e ac tion Mi c roflui d ic Motor D ri ven

Cost 4 2 5

Flow Rate 4 4 4

Performance 3 5 4

Size/Appearance 5 4 3

Ease of Use 5 3 4

Programmable 2 4 5

Totals 23 22 25


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Future Work Motor Driven Pump

Purchase componentsFabricate circuit

Design and produce casingTry to make waterproof Identify feedback mechanism

Minimize size


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Future Work Reaction Pump


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Future Work Reaction Pump

Want this to happen as quicklyas possible

A=A0e -kt


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References Adair, T. H. and A. C. Guyton. 1985. Measurement of subcutaneous tissue fluid pressure using a skin cup method. Journal of Applied

Physiology, 58 :1528-1535.Combining Chemistry with O ptics. 2005. The Whitaker Foundation. .Diabetes - The Disorder. 2005. Columbia Encyclopedia. .Haggerty, Michael, et al. Insulin Drug Pump. 27 Dec. 2004. UW-Madison, Dept. of Biomedical Engineering.

.How to Take Insulin. 2005. dlife.com.

.Johnson, Jason. How Stepper Motors Work. 2005. .Jones, Douglas W. Stepping Motor Physics. 2005. University of Iowa - Dept. of Computer Science.

.Laser, D. J. and J. G. Santiago. 2004. A review of micropumps. J Micromech Microengineering 14 :35-64.Liepmann, D., A. P. Pisano, and B. Sage. 1999. Microelectromechanical Systems Technology to Deliver Insulin. Diabetes Technology &

Therapeutics 1 :469-476.MacDonald, Michael M. Personal interview. 26 Jan. 2005.Stepper Motors. 2004. ERNTEC Pty Ltd. .Stepper Motors. 2005. AllMotion Inc. .Tay, F. E. H., W. O . Choong, H. Liu, and G. L. Xu. 2000. An intelligent micro-fluidic system for drug delivery, p. 70-5. I n Anonymous

Proceedings of IEEE International Conference on Industrial Technology 2000, 19-22 Jan. 2000. Jaico Publishing House, Goa,India.

Treating Complications. 2005. The Whitaker Foundation. .what is diabetes? 2005. Juvenile Diabetes Research Foundation International. .

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disposable drug delivery system