NOVEL AMPHIPHILIC MICROGELS FABRICATED VIA ON-CHIP POLYMERISATION Bingyuan Lu 1 , Mark D. Tarn 1 , Nicole Pamme 1* and Theoni K. Georgiou 2 1 Department of Chemistry, University of Hull, UK 2 Department of Materials, Imperial College London, UK ABSTRACT We report the on-chip polymerisation of hydrophobic microgels from precursor droplets, and their downstream synthesis to pH-responsive amphiphilic microgels for drug delivery. This elegant platform offers superior control over microgel properties, including size, crosslinking density and hydrophobic/hydrophilic properties. The encapsulation and release of hydrophilic (Trypan Blue) and hydrophobic (Sudan Red) dyes based on the microgel shrinking/swelling properties was also studied. KEYWORDS: Amphiphilic microgels, On-chip polymerisation, Drug release, pH responsiveness INTRODUCTION Microgels are 3-dimensionally crosslinked polymer microparticles that can be used as drug delivery vehicles [1]. They can be responsive to specific stimuli such as pH, temperature and electric fields, depending on the types functional groups present. Conventional bulk synthesis methods yield microgels in large size distributions (coefficient of variation (CV) 5-30 %) and offer only limited control over the internal chemistry. Droplet microfluidics can overcome these issues by enabling the generation of monodispersed droplets (CV ~3 %) that, when loaded with precursors, can be polymerised downstream [2]. Nonetheless, the synthesis of amphiphilic microgels, useful for both hydrophilic and hydrophobic drug delivery, is typically achieved in a two-step modification that provides poor control over the hydrophobic/hydrophilic ratio and crosslinking density [3]. We have previously demonstrated the synthesis of amphiphilic microgels, based on hydrophilic chains and hydrophobic crosslinks, with controlled hydrophobicity from droplets generated on-chip followed by off-chip polymerisation [4]. Here, we report a far superior process for the synthesis of pH-responsive amphiphilic acrylic acid- butyl acrylate-ethylene glycol dimethacrylate (AA-BuA-EGDMA) microgels, in which hydrophobic droplets generated on-chip undergo immediate polymerisation within the microchannels. The microgels were rendered amphiphilic via a simple one-step hydrolysation process. This elegant platform offers superior control over microgel properties, including their size, hydrophilic/hydrophobic ratio, and crosslinking density. Furthermore, these microgels, unlike in our previous study, also contain hydrophobic groups in the backbone chains on the microgel and not only at the crosslinks. Figure 1: (a) Exploded schematic of the microfluidic device, featuring a flow focusing junction and serpentine channel in the top layer (10 μm deep, 30 μm wide), and the serpentine channel (50 μm deep, 800 μm wide, 2 m long) mirrored in the bottom layer. (b) Photograph of the microfluidic chip fabricated in glass. (c) Schematic showing the principle of droplet generation with in situ UV polymerisation to form microgels. EXPERIMENTAL A flow-focusing glass chip was used for droplet generation and polymerisation, which featured two layers (Fig. 1a,b): a top layer containing a flow-focusing junction and serpentine channel (30 μm deep, 10 μm wide), with the serpentine channel mirrored in the bottom layer (60 μm deep, 800 μm wide). The 1044 978-0-9798064-8-3/μTAS 2015/$20©15CBMS-0001 19 th International Conference on Miniaturized Systems for Chemistry and Life Sciences October 25-29, 2015, Gyeongju, KOREA