Formation of Microparticles using a Heat Sensitive Gel in a Microfluidic Device

77th Annual Meeting of The Society of RheologyVancouver, British Columbia, Canada

October 16 - 20, 2005

Gordon Christopher and Shelley L. Anna

Department of Mechanical EngineeringCarnegie Mellon University, Pittsburgh, PA 15213

Droplet Formation in Microfluidic T-Junctions

• Shearing leads to drops• Ease of fabrication/operation• Droplet size monodisperse and

controllable

Dispersed Phase

Continuous Phase

Year Author Device Dispersed

2000 Sugiura et al., Proc. Microtech. In Medicine and Biology, 2000

Heated Array Tripalmitin

2002 Nisisako et al., Proc. SICE, 2002

T-Junction with UV Initiation

Lauryl Acrylate

2005 Dendukuri et al., Langmuir, 2005

T-Junction UV Initiation

Optical Glue

2005 Xu et al., Angew. Chem., 2005

Flow Focuser with cooling

Agarose Bismuth

Possible Applications for Microscale Particles

• Drugs composed of protein susceptible to:

– Enzymes

– Acid in Stomach• Solution encapsulate (Patil et al., Journal of Polymer

Science,1999)

Monodispersed drop size

Controlled Dosage and Diffusion

Dispersed Phase with Drug

Collect

Drug Diffuses controlled by drop sizes

Drug Delivery

Microfluidic Probe of Fast Gel Kinetics?• Thermoreversible gelation processes:

– Phase separation

– Crosslinking

– Conformation Change • Rates affect final gel morphology (Manno et

al., Phys. Rev. E., 1999)

• Morphology domains order of 10-15μm (Bansil and Lal, Poly., 1992)

Make microscale drops

Heat in microfluidic device

Confinement and Quench Rates impossible in

Macroscale Rheometers

0.1

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100

1000

0.01 0.1 1 10 100 1000

0.1

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100

1000

0.01 0.1 1 10 100 1000

Strongly Shear Thinning

763.9.22

Shear Rate

Effe

ctiv

e V

isco

sity

(P

a•s

ec)

][sec 1

Drop size dependent on

Drop Size

D

D Constant

•Gels with thermal hysteresis– Agarose– Carrageenan: κ,λ,ι

•Water soluble – i-Car: soluble with Ca2+

(Hossain, Biomacro.,2001)

•Applications: biotechnology and consumer products…

Ti-Car Repeat Unit

(Patil et al., Journal of Polymer Science,1999)

Measuring Gel Particle Properties

Agarose Particles•Packing•Non-Spherical Shapes

PDMS, Qc=600

i-Car, Qd=60

i-Car, Qd=40

PDMS, Qc=400

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L

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