On-Chip Light Modulation Applying Optofluidic Principles

Optofluidics is a promising approach for the realization of novel and versatile lab-on-a-chip devices. We present optofluidic switches for reconfigurable on-chip light modulation. Compared with other researches mechanically moving elements were entirely omitted which reduces wearing and eliminates any sticking issues completely. The first modulator is based on the hydrodynamic control of streams of liquids in a microfluidic channel. Properly choosing the refractive index of the employed liquids allows light guidance in a core stream that can be steered in the channel. The advanced device is based on total internal reflection at the solid-liquid interface of a liquid filled microfluidic channel. Depending on the refractive index of the fluid, light is either reflected and guided toward the first output or transmitted and routed to another position. Placing two channels after each other provides three possible optical outputs. Compared with the hydrodynamic realization, the consumption of liquids is kept at the very minimum because no permanent flow through the device is needed. Fluorescence images were taken to evaluate the operation of the devices. Both principles can be upgraded in terms of light modulation possibilities by either increasing the width of the channel in the hydrodynamic realization or integration of more than two channels into the advanced modulator.