"On-the-Fly" Fabrication of Highly-Ordered Interconnected Cylindrical and Spherical Porous Microparticles via Dual Polymerization Zone Microfluidics.

Shahriar Sajjadi,Fatemeh Jahanzad,Mohammad Alroaithi,Ankur S Chaurasia

doi:10.1021/acs.langmuir.9b01077

Abstract

A microfluidic platform with dual photopolymerization zones has been developed for production of novel uniform interconnected porous particles with shapes imposed either by the geometry of the external capillary or by the thermodynamic minimization of interfacial area. Double w/o/w (water/oil/water) drops with well-defined internal droplet size and number were produced and then exposed to online photopolymerization to create the porous particles. Cylindrical interconnected porous particles were produced in a segmented flow where the drops took the shape of the capillary. The microfluidic setup included an extension capillary where the drops relaxed and conformed to their thermodynamically favored morphology. Window opening of the particles occurred "on-the-fly" during UV polymerization without using any offline auxiliary methods. A distinction was made between critically and highly packed arrangements in double drops. The window opening occurred consistently for highly packed spherical drops, but only for critically packed drops containing more than six internal cores at internal phase ratios as low as 0.35. The size and number of cores and shape and structure of double drops could be precisely tuned by the flow rate and by packing structure of the inner droplets.

Highlights

Jahanzad, Fatemeh; London South Bank University, Applied Science “On-The-Fly” Fabrication of Highly-Ordered Interconnected Cylindrical and Spherical
Porous microparticles resulting from droplet polymerization suffer from a low uniformity in both void/window and final particles sizes, whereas seed swelling method, which benefits from a facile generation of uniform nano or micro particles, is limited to microspheres below 10 μm, and to non-uniform
We demonstrate a two-zone microfluidic generation of cylindrical and spherical/non-spherical drops containing various numbers of internal droplets, followed by their UV polymerization on-the-fly to form open porous microparticles

Summary

INTRODUCTION

Porous materials have already been estabished as interesting area of research due to their distinctive permeable structure within a polymer matrix. They are characterised by the presence of pores with a wide range of sizes usually within 2-50 nm, and enjoy several advantages over impermeable substances, including light weight, a network of well-connected pores, high surface area and excellent absorption capacity.[1,2,3] Porous polymeric particles, which are miniature porous entities, are increasingly becoming an interesting area of research due to their smaller size and increased permeability They have attracted enormous applications including ion exchange resin[4], separation and filtration[5], encapsulation agents for controlled release of drugs[6], catalysts[7] or supports for catalysts[8], and packing materials in chromatography industries.[9,10,11,12] Another class of porous particles, arguably called macroporous or cellular particles, contains large voids or cavities and enjoys having wide pores often called windows. To produce interconnected windows at relatively low internal phase ratio, the emulsion formulation was manipulated by equalling the inner and outer interfacial tensions This triggered the collapse of droplets-drop interface during polymerization and exposed the hollow interiors of microparticles. The capillaries through which oil was flown were made hydrophobic by treatment with n-octadecyltrimethoxysilane while the surface of the capillary where the water went through was made hydrophilic by plasma treatment (Femto Plasma cleaner, Diener)

Procedure

Findings

CONCLUSION