Recently, one of world famous top scientific journals in microfluidic field, “Lab on a Chip” published a research paper from “Laboratory of Advanced Photonic Materials and Physics” led by Professor Xianfeng Chen entitled “Characterization of microdroplets using optofluidic signals” (Lab Chip 12 (19), 3816-3820 (2012)). “Lab on a Chip” provides a unique forum for the publication of significant and original work related to miniaturisation (on and off chips) at the micro- and nano-scale across a variety of disciplines, including chemistry, biology, bioengineering, physics, electronics, clinical/medical science, (bio)chemical engineering and materials science, which causes great attention by the researchers worldwide.

Optofluidics fundamentally aims at manipulating fluids and light at the microscale and exploiting their interaction to create highly versatile systems. It is the frontier multidisciplinary science and technology of modern optics, optoelectronics and microfluidics. Due to the unique features of optofluidics such as a wide choice of liquid compositions and shapes, smooth liquid-liquid optical interface, less liquid consumption and easy integration, various kinds of optofluidic devices such as dye lasers, interferometers and sensors have attracted great attention and have been applied in various fields including chemistry, biology, medicine and physics.

Droplet microfluidics has drawn much attention due to its distinctive properties in compartmentalizing and performing typical laboratory operations in a nano- and pico-liter volume droplets, offering new routes for studying micro-size reaction processes as microreactors. Owing to the fast generation of microdroplets, the droplet features usually can only be observed under a high speed CCD camera, restricted by the high cost and limited storage space. In order to solve this problem, Professor Xianfeng Chen’s group introduced a simple method to characterize microdroplets using a typical on-chip micro cytometer design via optofluidic techniques. Different sizes of microdroplets are generated through a typical microfluidic T-junction by adjusting the flow rates of the two immiscible liquids. Droplet size and content can be determined by monitoring the optofluidic signals reflected at the fluid-PDMS interface, which makes it possible for long time real-time monitoring and characterization of microdroplets without using a high speed CCD camera. The convenience in integration with a wide range of state-of-the-art optofluidic elements on a chip makes the device have broad applications in both droplet microfluidics and micro total analysis systems.