Solvent-tunable PDMS microlens fabricated by femtosecond laser direct writing

Reported here is the fabrication of solvent-tunable polydimethylsiloxane (PDMS) microlenses using the femtosecond laser direct writing (FsLDW) technique. PDMS microlenses with equation-defined profiles, including both spherical microlens and aspheric hyperboloid microlens, have been fabricated according to preprogrammed models. In addition to excellent optical performance derived from the high accuracy and smooth surface, the resultant PDMS microlenses also show unique solvent-tunable properties; the focal length could be dynamically tuned by organic solvents of different solubility parameters. To obtain better control over the tunable property, a PDMS microlens has been flexibly integrated with a microfluidic device. Under the stimulation of different solvents, its tunable imaging performance has been demonstrated in a controlled manner.