Multilayer polymer light guides integrated with refractive microlenses and liquid by micromolding and inkjet printing

Optofluidic behavior has been studied over a decade for the transmission of light through fluidic channels by virtue of versatile fabrication schemes such as (soft-) lithography techniques. One of the crucial factors in the consideration of device design involves the use of a fluidic core filled into the solid channels to effectively control the planar direction of light guiding based on total internal reflection (TIR). However, there are still few studies investigating the optical performance of light transmission associated with an optofluidic design for bifurcation and out-of-plane transmission of light beams. This paper reports a droplet filling method that can significantly improve the controllability over the formation of liquid flow and solid convex lenses utilizing the polydimethylsiloxane (PDMS) layers fabricated by soft-lithography technique. Analytical and experimental and results indicate that the curvatures of hemispherical profiles for the refractive microlenses formed were simply varied by different droplet volumes (single droplet of 1-10 pl) placed on the cavity-structured surfaces, thus providing the capability of control over volumes in design. In this way, the individual LGs fabricated from the micromolding and inkjet printing could be applied in many applications, in particular the future lab-on-a-chip (LOC) microsystem and micrototal analysis system (μTAS).