We actuate with light & magnets, we fold & unfold DNA, we cell-free express proteins, we play with drops, marbles & interfaces, we organize particles, we harness coffee rings.

Light-driven microfluidics

We develop laser-free methods where a simle light illumination stimulus (e.g., from a LED device) is used to control, manipulate, drive, divide and mix continuous flows (light-driven microfluidics) or discrete droplets (digital optofluidics).

Light-driven microfluidics
1. Digital optofluidics

At the macro-scale, we use light to induce interfacial tension gradients between an oil and a water phase conaining a photosensitive surfactant. This results in light-induced Marangoni flows able to make macroscopic droplets move in a controlled fashion. This allows us to manipulate millimetric droplets, at a controllable speed (up to 0.3 mm/s), along any desired trajectories. The picture above is a stack of images of a 5 µL oil droplet (gold color) floating on a water bath and moved by a light trap (cyan halo) along a heart-shaped path. We apply this for manipulation of biological objects, safe handling of liquids, and development of new light-driven machines.

Reversible, wavelength-dependent motion of a droplet. This video shows a 5 µL oil droplet, on a photosensitive surfactant-laden solution, pushed and pulled by light depending on the wavelength of the illumination. Illumination is applied and maintained on the left-hand part of the droplet. At the beginning, UV light is applied, an interfacial tension gradient is created toward the left direction, which induces drolet motion to the right (the droplet is pushed by UV). After a while, the illumination is changed to blue wavelength, the interfacial tension gradient is now oriented towar the right direction, which induces droplet motion to the left (the droplet is pulled by blue light). This video is displayed at 4x speed and the droplet moves at a speed around 300 µm/s. The Petri dish is 2.5 cm in diameter.

Macroscopic optical tweezer. In this video, a two color illumination is created so that the center part of the droplet is under blue illumination (attraction) while the droplet is surrounded by a UV halo (repulsion). This two-color illumination creates a capillary trap and the droplet can be moved at will around a desired trajectory. Here, the droplet is moved along a N-shaped path. This video is displayed at 8x speed. The Petri dish is 2.5 cm in diameter.

2. Light-driven microfluidics

Optofluidics usually refers to the use of fluids as optical elements, especially in microfluidic device. We propose to develop a new field, that we call light-driven microfluidics, where light can serve as an actuator of fluids. For instance, we have demonstrated the possibility to control microdroplet generation in microfluidic devices using light (see the third video). We have also developed the first reversible microfluidic mixing triggered by a simple illumination (see the fourth video). Note that the illumination is simply provided by an external LED illumination device and does not require any laser nor optical set-up, making our approach particularly portable, robust and flexible.

Photo-actuation of nanoliter microdroplets. In this video a continuous laminar microfluidic flow is reversibly fragmentaed into water-in-oil microdroplets by UV illumination at 365 nm.

UV-triggered microfluidic mixing Two oil phases are reversibly mixed upon UV-induced generation of water droplets.


Microfluidic mixing triggered by an external LED illumination
A. Venancio-Marques, F. Barbaud, D. Baigl*, J. Am. Chem. Soc. 2013, doi : 10.1021/ja311837r -
First reversible microfluidic mixing triggered by a simple illumination (LED)

Photo-actuation of liquids for light-driven microfluidics: state of the art and perspectives
D. Baigl*, Lab Chip 2012, doi : 10.1039/C2LC40596B -
A comprehensive review on light-driven microfludics

Photoreversible Fragmentation of a Liquid Interface for Micro-Droplet Generation by Light Actuation
A. Diguet, H. Li, N. Queyriaux, Y. Chen, D. Baigl*, Lab Chip 2011,11, 2666-2669 - doi : 10.1039/C1LC20328B -
Light-controlled actuation and generation of drolets in a microfluidic device based on photo-dependent wetting

Photomanipulation of a Droplet by the Chromocapillary Effect
A. Diguet, R.-M. Guillermic, N. Magome, A. Saint-Jalmes, Y. Chen, K. Yoshikawa, D. Baigl*, Angew. Chem. Int. Ed. 2009, 48, 9281-9284 - doi : 10.1002/anie.200904868 -
Fast and controlled manipulation of macroscopic droplets using light based on a photo-induced Marangoni effect