Microfluidic devices and methods are provided for enhancing detection of a diffusion pattern formed by particles diffusing between at least two fluid streams in parallel laminar flow such that an interface is formed between them by increasing the dimension of the streams in the diffusion direction. This may be accomplished by flowing the streams through a transforming turn, or by flowing the streams through a channel having diverging walls. Devices and methods are also provided for enhancing diffusion between two streams comprising changing the interface between said streams from a narrow interface to a broad interface.