Microchip for Drug Delivery

Microchip for Drug Delivery









Ramille M. Capito

Leah Lucas

ME 395 MEMS Spring 2000

Presentation Outline





I. Introduction: Why the use of a microchip?

II. Microchip Design/Microfabrication

III. Gold Dissolution

IV. Circuit Design

V. Power Source

VI. 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  Each reservoir is capped

with a conductive membrane

 biocompatible and small (i.e. gold) and wired with the

enough to be implantable final circuitry controlled by a

in the human body microprocessor.





A strong, non-

degradable, easily

etched substrate that is

impermeable to the

delivered chemicals

and non-degradable to

the surrounding

environment within the  The substrate contains multiple reservoirs

body is silicon. 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 ECR-

enhanced 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

(0.3-0.5 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.