Formation of Microparticles using a Heat Sensitive Gel in a Microfluidic Device 77 th Annual Meeting of The Society of Rheology Vancouver, British Columbia, Canada October , 2005 Gordon Christopher and Shelley L. Anna Department of Mechanical Engineering Carnegie 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 YearAuthorDeviceDispersed 2000Sugiura et al., Proc. Microtech. In Medicine and Biology, 2000 Heated ArrayTripalmitin 2002Nisisako et al., Proc. SICE, 2002 T-Junction with UV Initiation Lauryl Acrylate 2005Dendukuri et al., Langmuir, 2005 T-Junction UV Initiation Optical Glue 2005Xu 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

Strongly Shear Thinning Shear Rate Effective Viscosity (Pasec) Drop size dependent on Drop Size Constant Gels with thermal hysteresis –Agarose –Carrageenan: κ,λ,ι Water soluble –i-Car: soluble with Ca 2+ (Hossain, Biomacro.,2001) Applications: biotechnology and consumer products… i-Car Repeat Unit (Patil et al., Journal of Polymer Science,1999)

Measuring Gel Particle Properties Agarose Particles Packing Non-Spherical Shapes PDMS, Q c =600 i-Car, Q d =60 i-Car, Q d =40 PDMS, Q c =400