Transcript Microchip for Drug Delivery

Microchip for Drug Delivery
Ramille M. Capito
Leah Lucas
ME 395 MEMS Spring 2000
Presentation Outline
I.
II.
III.
IV.
V.
VI.
Introduction: Why the use of a microchip?
Microchip Design/Microfabrication
Gold Dissolution
Circuit Design
Power Source
Conclusions
Drug Delivery
 Very important aspect of medical treatment.
 Drug effectiveness directly related to the way in which
drugs are administered
--can make it very difficult to select the proper drug
delivery system.
 Some therapies require that the drug be repeatedly
administered to the patient over a long period of time, or
in specific amounts at a time in order to maximize drug
effectiveness.
Problems with Current Methods of
Drug Delivery
 In many cases, patients often forget, are unwilling, or
are unable to take their medication
 Some drugs too potent for systemic drug
delivery (intravenous) and may cause
more harm than good
 Great advantage: a drug delivery device that is
capable of controlled, pulsatile or continuous release of
a wide variety of drugs and other therapeutics that can
be safely implanted inside the body
Other Drug Delivery Systems Attempting to
Control Drug Release
 Polymeric devices:
Problem: too simple to have the ability to
precisely control the amount or rate of
drug released.
Electromechanically driven devices:
Problem: miniature power-driven
mechanical parts required to either
retract, dispense, or pump in order
to deliver drugs in the body 
complicated and are subject to
breakdown (i.e. fatigue or fracture).
--complexity and size restrictions 
unsuitable to deliver more than a few drugs
or drug mixtures at a time.
What is Novel About this Microchip?
 It is the first device of its kind enabling the
storage of one or more compounds inside of
the microchip in any form (solid, liquid, or
gel), with the release of the compounds
achieved on demand and with no moving
parts.
Microchip Design

simple to use and manufacture

biocompatible and small
enough to be implantable in
the human body
A strong, nondegradable, easily etched
substrate that is
impermeable to the
delivered chemicals and
non-degradable to the
surrounding environment
within the body is silicon.
 Each reservoir is capped with a
conductive membrane (i.e. gold)
and wired with the final circuitry
controlled by a microprocessor.
 The substrate contains multiple reservoirs capable of
holding chemicals in the solid, liquid, or gel form.
 delivery of drugs for weeks or years at a time
 varying dosages—should release substances in a
controlled dependable manner
Microfabrication Process
1.) Deposit layer of insulating material,
silicon nitride (0.12 mm), onto the
substrate by PECVD
2.) Pattern by photolithography and
square reservoirs are etched by ECRenhanced RIE
3.) With potassium hydroxide solution at
85C, anisotropically etch square
pyramidal reservoirs into the silicon along
the (111) crystal
4.) Invert and deposit gold electrodes (0.30.5 mm thick). Pattern by E-beam
evaporation and liftoff.
5.) Deposit electrode protective coating,
silicon dioxide, by PECVD. Silicon dioxide
over anode, cathode and bonding pads are
etched with ECR-enhanced RIE to expose
gold film.
6.) Remove SiN layer in the inside of
reservoir by RIE to expose gold
membrane.
7.) Fill reservoirs by inkjet printing
through opening (500 mm x 500 mm)
Reservoir Filling
PV = nRT
Substrate
Vapor
Bubble
Heater
Drug
Microfabrication Process (cont’d)
8.) Bottom of reservoirs capped with a
silicon nitride coating
9.) Device can now be patterned with IC
control circuitry and thin-film battery.
Why the Gold Membrane?
is chosen as the model membrane material:
 It is easily deposited and patterned
 Gold has a low reactivity with other substances and resists spontaneous corrosion in
many solutions over the entire pH range.
 The presence of a small amount of chloride ion creates an electric potential region
which favors the formation of soluble gold chloride complexes.
 Holding the anode potential in this corrosion region enables reproducible gold
dissolution.
--Potentials below this region are too low to cause appreciable corrosion, whereas
potentials above this region result in gas evolution and formation of a passivating
gold oxide layer that causes corrosion to slow or stop.
 Gold has also been shown to be a biocompatible material.