Disposable Drug Delivery System

1
Disposable Drug Delivery System

• Ross Gerber, Aman Ghotra
• Karim Mahamud, Prakash Rao
• Client Michael MacDonald, MD
• Dept. of Pediatrics UW Hospital
  Clinics
• Advisor William Murphy, PhD
• Dept. of Biomedical Engineering

2
Outline

• Background
• Insulin, Type I diabetes, drug delivering devices
• Problem Statement
• Design Constraints, Motivation
• Proposed Design Solutions
• Reaction Pump
• Microfluidic Pump
• Motor Driven Pump
• Evaluation
• Future Work

3
Background

• Insulin
• Produced in Pancreas
• Essential protein for glucose regulation
• Low insulin levels can lead to coma or death
• Type I Diabetes
• Autoimmune Disease that stops insulin production
• Affects children and young adults
• Patients must inject insulin periodically

4
Background (cont.)

• Current Insulin Delivering Devices
• Syringes
• Insulin Pens
• Insulin jet injectors
• Insulin pumps
• Have a small reservoir, syringe, programmable
  hand pad
• Commonly used by Type I diabetics

5
Problem Statement

• Develop a small, automatic, inexpensive (and
  possibly disposable) drug delivery system that
  can give a continuous flow of a protein-based
  drug over period of twenty-four hours.

6
Design Constraints

• A new insulin drug pump must
• Deliver solutions at a constant rate for over a
  period of 8-24 hours at 10-100 µL/hr
• Hold up to 0.5 ml of total solution
• Not be bulky or heavy
• Be cost-efficient (maximum cost 1000.00)
• Be user friendly
• Be easily sterilized

7
Motivation

• Current insulin pump users are dissatisfied, as
  they
• Do not provide constant flow rates
• Are expensive (5,000-7,500)

8
Design 1 Reaction Pump

• Spring generates force
• As solid organic compound dissolves, spring is
  allowed to work
• Reaction is initiated when glass membrane is
  broken
• Rate of reaction determines the rate of delivery

9
Progress of Dissolution
Compounds near end of reaction t8hr
Compounds at beginning of reaction t1hr
Compounds before reaction t0
View of diffusion grate
10
Reaction Pump Components

• Spring (1)
• Liquid Reactant (2)
• Solid Reactant (3)
• Plunger and Grate (4)
• Insulin (5)
• Chamber (6)
• Start Pin (7)

11
Reaction Pump Mechanism

• Button (7) is pushed to brake thin membrane (9)
• Water layer (2) is exposed to dissolvable organic
  compound (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) out of chamber (6) into the recipient

12
Reaction Pump Evaluation

• Advantages
• Very small
• Constant rate
• Disposable
• No electronics
• Easy to use
• Can vary amount of insulin delivered by
  concentration

• Disadvantages
• Must determine chemical reaction
• No feedback mechanism
• Insulin can possibly be forced in if an external
  force is applied
• Could fall off

13
Microfluidic System

• Components
• Micro-pump
• Reciprocating Displacement type
• Passive micro-valve
• Control Circuit
• Can precise and controllable amount of fluid in
  the range of µL/min mL/min

14
Reciprocating Micropump Operation

• Moving surface does pressure work on working
  fluid in periodic manner
• Force-applying moving surface deformable plate
  (pump diaphragm)
• Basic components pump chamber (on 1 side of
  pump diaphragm), actuator mechanism, and 2
  passive check valves

15
Piezoelectric Actuator Mechanism

• Piezoelectric Excitation
• If material subjected to mechanical tension,
  electrical polarization proportional to extension
  would occur
• Opposite also holds true, where material
  deformation occurs as a result of applied
  electric field (inverse piezoelectric effect)
• PZT, ZnO
• Can be used to bend diaphragm

16
Piezoelectric Actuator Mechanism (cont.)

• Operation
• Driver acts on diaphragm to alternate increase
  decrease of pump chamber volume
• Fluid drawn into pump chamber during fluid intake
  stroke (diaphragm expands), and force out during
  discharge stroke (diaphragm contracts)
• Check valves _at_ inlet and outlet favor
  bidirectional flow, thereby rectifying the flow
  over a two-stroke pump cycle

17
Evaluation - Microfluidic Pump

• Advantages
• Very small
• Accurate delivery
• Would essentially act as an artificial pancreas

• Disadvantages
• Too expensive for disposable use
• Closed loop feedback control with glucose sensor
  is still years away
• Very difficult to fabricate

18
Design 3 Motor Driven Pump

• Components
• Syringe
• Tubing
• Programmable Electronic Circuit
• PC can change flow rates
• A circuit is responsible for converting step and
  direction signals into winding energized patterns
• Stepping motor
• Rotates counter-clockwise and clockwise
• Variable steps (½, ¼, etc.)
• Smaller steps provide more torque

19
Motor Driven Pump

• Components (cont)
• Converter
• Converts rotational motion into linear motion
• Drives the syringe which delivers insulin

20
Evaluation Motor Driven Pump

• Advantages
• Inexpensive (350)
• Small
• Size
• Easy to sterilize
• Provides constant rate

• Disadvantages
• Not waterproof
• Bathing, swimming
• Not effective during meal times

21
Decision Matrix
22
Future Work Motor Driven Pump

• Purchase components
• Fabricate circuit
• Design and produce casing
• Try to make waterproof
• Identify feedback mechanism
• Minimize size

23
Future Work Reaction Pump
24
Future Work Reaction Pump
AA0e-kt
Want this to happen as quickly as possible
25
Questions?
26
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