Disclosed herein are methods for array assembly and detection. The methods can use an incubation chamber containing a suspension of nucleic acid targets, polymerase and a set of oligonucleotide probes bound to magnetic beads in a randomly dispersed state. Each probe can have a target binding domain that is complementary to a target nucleic acid, a closing domain with a sequence that is complementary to the sequence of the target binding domain, and a joining region between the binding domain and the closing domain, which is not complementary to the target nucleic acid. Method steps can include providing the incubation chamber, placing the incubation chamber in a magnetic trap, generating a magnetic field that induces the magnetic beads to migrate towards a substrate and, once in proximity to the substrate, to interact with each other repulsively and reorganize into arrays, and imaging the array.