The Research Of Microfluid Driving Method Based On The Wettability Of TiO₂Nanomaterials

Microfluidic systems have been wildly used for biomedical research and chemicalsynthesis, such as genetic analysis, drug discovery, food safety, environmentalmonitoring and chemistry reaction. As an interdisciplinary filed, the study on themicrofluidic systems has greatly aroused people’s interest in the past decade. Fluiddriving is the critical unit operation in a microfluidic system and the prerequisite andfoundation for fluidic accurate control. Based on the cohesion-tension theory in plantphysiology, a microfluid surface-tension driven method, which imitated thehydrophilic structure in plant leaves, utilized the wettability of TiO₂nanomaterials,was developed and presented in the paper.TiO₂nanoparticle thin film was patterned using pulsed laser deposition （PLD） on aglass microfluidic chip which was manufactured through lithography and wet etchingprocedure and integrated with a capillary micropump. The effect of TiO₂nanoparticlethin film on the wettability of glass microfluidic chip was investigated. The fluidvelocity in the microchannels was tested using a self-developed monitoring system.The results showed that the photoinduced hydrophilicity of TiO₂nanopartical thinfilm was the cause of the enhanced hydrophilicity in the microchannels. As a result,the microfluid in the microchannels can be driven by the increased surface tension.The highest fluid velocity of50mm/s in the microchannels was achieved via velocitytesting.Metal microfluidic chips, which were fabricated using lithography and laserablation respectively, were also presented in this paper. TiO₂nanotube （TNT） thinfilm was grown on the metal microfluidic chips through anodic oxidation. Themachining effect of different processes is compared and the influence factorsincluding nanotube diameter, storage time, and light illumination condition on thewettability of the nanotube were studied. The fluid velocity in the microchannels wastested using the same equipment mentioned above. The results showed that thehydrophilicity of the microchannels can be strengthened by the TiO₂nanotube thinfilm, leading to high surface tension, which could be used to drive microfluid inmicrochannels. A fluid velocity that was faster than15mm/s was obtained in themicrochannels. The feasibility of the TiO₂nanotube enhanced surface-tension drivenmethod was verified.