(a) providing the analyte fluid comprising the analyte particles;

(b) providing a diffusion fluid comprising binding particles capable of binding with the analyte particles;

(c) flowing the analyte fluid and the diffusion fluid in adjacent laminar flow through a microfluidic channel;

(d) allowing the analyte particles to diffuse into the diffusion fluid and bind with the binding particles to form analyte/binding particle complexes;

(e) allowing the analyte/binding particle complexes to cross-link to form cross-linked aggregates; and

(f) detecting the presence of the analyte particles and the cross-linked aggregates,

wherein:

each of the binding particles is capable of binding with more than one analyte particle;

each of the analyte particles is capable of binding with more than one binding particle;

the non-aggregated analyte/binding particle complexes and the analyte particles are at least the same order of magnitude in size and have diffusion coefficients that are essentially the same; and

the cross-linked aggregates have a diffusion coefficient that is at least two times greater than the diffusion coefficients of the non-aggregated analyte/binding particle complexes and the analyte particles.