We demonstrate an optofluidic variable-focus microlens formed by a solid polydimethylsiloxane (PDMS) meniscus channel wall and a tunable liquid lens body. A novel method for in situ fabrication of the meniscus channel wall is developed by introducing liquid PDMS prepolymer into a microchannel followed by curing. Three-light manipulation techniques including tunable optical focusing, collimating, and diverging are realized by varying the refractive index (RI) of liquid lens body. Also, we present an absorption measurement of methylene blue (MB) with a collimated probing light, achieving a detection limit of 0.25 μM by using a 5-mm-long detection cell.