| Abstract | Micro and nano electromechanical system (MEMS and NEMS) based microfluidic
devices are gaining popularity from last few years in biomedicine because of small size,
light weight, low cost, ease of fabrication, accuracy, high efficiency and more reliability.
Due to these attributes, MEMS and NEMS devices have unobtrusively and efficiently
made their way into our daily lives. Appliances, automotives, electronic instrummentation,
telecommuications, aeroscope, sensors technology, inkjet printing technology, office
equipment, industrial process control, micro and nano fluidics devices, medical devices
and system are few examples. Micro and nanofluidic systems deal with the fluid flow in
diminutive amounts typically few microlitres (µL) to nanoliters (nL) in a miniaturized
system. The main functions perfumed by these systems are sample preparation,
purification, separation, reaction, transport, immobilization, labeling, biosensing and
detection. Micro and nanofluidic devices are promising to meet the critical medical needs
such as site specific dmg delive1y, reduced side effects, increased bioavailability and
therapeutic effectiveness. Transdermal drug delive1y (TDD) is an attractive way to transfer
the pharmaceutical compound by reducing pain, gastrointestinal absorption, liver
metabolism, gastrointestinal and degradation. TDD system consists of micropumps,
microneedles, drug reservoir, flow sensors, blood pressure sensors and electronic module.
Microneedles and micropumps are two major and essential components of TDD system.
Microneedles are used as an interface to transport the dmg from reservoir to patient body.
Microneedles can be categorized according to their structure, fabrication process,
materials, overall shape, tip shape, size and applications. Micropumps are used to facilitate
the actuation mechanism for drug transportation. The important features of micropumps
are working principles, actuation methods, construction, performance parameters and
applications. Microneedles and micropumps are integrated to form TDD system. The aim
of this research is to design and fabricate MEMS based hollow out-of-plane silicon
microneedles for TDD system. Using ANSYS, structural and Multiphysics analyses have
been conducted before the fabrication process of microneedles to test the design suitability
for TDD. Simulation shows that the proposed design of microneedles is suitable for TDD.
During structural analysis, the results show that 6.69 GPa stress occurs at the microneedle
bottom with 20 µm deflection at the tip for applied force of 8.8 N. Numerical results show
that the presented design of tapered tip microneedles can easily bear· the shear, axial,
bending, :fictional and lateral forces equal to 8.8 N during penetration into the patient
body. Coupled field analysis of reservoir integrated with microneedle array using
piezoelectric actuator has also been perfo1med. The effects of frequency and voltage on
actuator and fluid flow rate through 6x6 microneedle a1rny have been investigated.
Multifield analysis shows that the maximum fluid flow rate of 612 µL/min is obtained at
applied voltage of 100 V through 6x6 microneedle array with actuator deflection of 12.24
µm. After the selection of suitable design of microneedles for TDD system, the actual
fabrication of tapered tip silicon hollow out-of-plane microneedles has been cru1ied out
using inductively coupled plasma (ICP) etching technology.
|