A photoactivable microfluidic device for heavy metal ion extraction Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8s45qc499

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  • The development of microfluidic devices for heavy metal extraction is presented in this dissertation. Various research areas, covering subjects from photochromic compound syntheses to microchip fabrication techniques are explored to develop microfluidic devices capable of extracting heavy metal ions from drinking water. Through integration of the beneficial characteristics of both microfluidic devices and photochromic dyes, a simple and innovative microchip configured as a photoactivable extraction system for metal ion accumulation and release can be realized. The initial research focused on the utilization of photochromic compounds namely spiropyrans, as chelators for heavy metal extraction. Spiropyrans are organic photochromic compounds that have been widely studied. Upon irradiation with UV or visible light, spiropyrans isomerize between the closed and open forms, in which the open form is comparatively more polar. Metal ions can influence this isomerization process by associating with the open form through the electron-rich oxygen atom. In contrast, visible light produces a high concentration of the closed form, and thus hinders metal-binding. Spiropyrans, therefore, show great potential as photo-reversible metal-complexation agents. The spiropyran derivatives were synthesized and immobilized on solid supports including polymeric resins and poly(methylmethacrylate) (PMMA) microchips. Metal ion uptake can be triggered using UV light and subsequently reversed on demand by shining green light on the colored complex, which regenerates the inactive spiropyran form resulting in the release of metal ions. The use of light to trigger the chelator offers unique opportunities. The work continued with the development of microfluidic fabrication for creating versatile, solvent-compatible microfluidic devices through surface modification. There are challenges associated with the use of polymeric based microfluidic devices, particularly in surface modification steps, as solvents can embrittle thermoplastics that resulting in microcracking. To overcome this limitation, we explored the possibility of fabricating extremely robust microfluidic devices entirely from fluorocarbon and glass materials. The work demonstrated a new fabrication technique based on a chemically activated poly(tetrafluoro ethylene) (PTFE) sheet sandwiched between chemically activated glass substrates. The PTFE microchannels can be fabricated in minutes using a cutting plotter to create microchannels. The possibility of glass to PTFE makes this method applicable in a wide range of applications.
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