Droplet formation system

A microfluidic system comprising:

• a microfluidic droplet channel to carry a flow of microfluidic droplets;
• a light source to illuminate the flow of microfluidic droplets with a beam of light comprising light having a range of wavelengths both above and below a predetermined threshold wavelength;
• a beam splitter configured to split light from the flow of microfluidic droplets into a first portion and a second portion, wherein the first portion comprises light above the predetermined threshold wavelength and wherein the second portion comprises light below the predetermined threshold wavelength;
• a camera configured to receive the first portion of the light;
• a photodetector configured to receive the second portion of the light, wherein an aperture is located in front of the photodetector;
• apparatus configured to process a signal from the photodetector;
• and
• a processor configured to determine a droplet frequency from fluctuations in the processed signal.

A microfluidic method of preparing a droplet, the method comprising:

• providing a flow of an emulsion of microfluidic droplets of a first droplet fluid within a carrier fluid in a microfluidic channel;
• determining a droplet dimension of a droplet in the flow of microfluidic droplets;
• providing a flow of a second droplet fluid to the microfluidic channel;
• fusing the droplet of the first droplet fluid with at least a portion of the second droplet fluid to obtain a fused droplet;
• determining a droplet dimension of the fused droplet;
• adjusting a pressure or flow rate of the flow of the emulsion of microfluidic droplets and/or a pressure or flow rate of the flow of the second droplet fluid in response to the determined fused droplet dimension.