Novel nonlinear magnetophoretic systems for on-chip separation and biosensing

Nonlinear magnetophoresis (NLM) is a recently introduced technique for onchiptransport and separation of superparamagnetic (SPM) beads based on atravelling magnetic eld wave generated by the combination of a micromagnetarray (MMA) and an applied rotating magnetic eld. The potential of this methodhas been demonstrated for the controlled transport and isolation of bead-labelled biological targets, such as, cells and exosomes. The high-resolution separation of dierent bead populations based on size, magnetic susceptibility, and presence of a captured analyte has also been reported.This PhD project aimed to develop and characterize dierent micromagnet designsfor the NLM transport of SPM beads and labelled biological targets, and to identifynovel separation and biosensing strategies. The SPM beads were used to capture different molecules, i.e. biotinylated bovine serum albumine and double stranded DNAfrom herpes-simplex-virus 1, and the induced bead aggregation provided a mean toisolate and detect the labelled analytes. With the NLM chip it was possible to separatethe unreacted beads from the beads carrying the target. These results showedthe potential of the technique to be used in magnetic bead aggregation (MBA) assaysand provided fabrication guidelines for the design of more complex arrays. Two innovative micromagnet designs were proposed that allowed SPM beads to be focusedand separated on-chip. These new architectures were used to rapidly collect the SPMbeads from a large region of the chip and focus them into synchronized lines, withthe aim of integrating a dedicated detection system. Tri{magnet switching junctionswere used to control the transport of the beads and to separate them based on theirsize in a continuous manner. The controlled transport of SPM bead-labelled singleMDA-MB-231 cells has also been demonstrated. The micromagnet designs presentedhere promise to allow more complex micromagnet networks to be developed, aimingtowards the creation of fully-functional miniaturized biosensors.