Axial magnetic levitation: A high-sensitive and maneuverable density-based analysis device

•An axial MagLev device with unified mathematical model is proposed.•The measurement sensitivity is increased by ∼20x through enlarging magnets’ separation distance.•The density of living cells is first measured by the axial MagLev device.•A non-destructive defects detection method via axial MagLev is demonstrated.•Ultrasonic measurement technique is combined with axial MagLev.