Abstract: In at least one illustrative embodiment, a method for contaminant detection includes distributing multiple magnetostrictive sensors on a nonmagnetic index plate. The index plate includes multiple wells formed in a top surface that are each sized to receive a magnetostrictive sensor. The method further includes placing a magnetic backing plate below the index plate, inverting the index plate and the magnetic backing plate, and then placing the inverted index plate on a sample surface. The sample surface may be two-dimensional food such as fresh vegetable leaves. The method may further include placing the index plate and the magnetic backing plate on a nonmagnetic cover plate that is positioned above a sensor coil. The method further includes removing the magnetic backing plate, removing the index plate, and applying a varying magnetic field with the sensor coil to a magnetostrictive sensor positioned on the cover plate. Other embodiments are described and claimed.