Irradiation methods and apparatus configured to deliver power, via electromagnetic fields at a variety of frequencies and power levels, in a localized fashion to a target area. In one example, an electromagnetic field generator is disposed on a substrate and configured to deliver power via electromagnetic energy to a thin region proximate to (above) a surface of the substrate, wherein electromagnetic field intensity decreases significantly beyond the thin region. Such methods and apparatus are particularly useful in a wide variety of processes involving chemical and/or physical interactions in connection with a sample of interest located in the thin region. In different aspects, irradiator apparatus may be configured as disposable devices, and/or used in combination with one or more microfluidic or sensing components, for a variety of medical/laboratory/diagnostic methods and instrumentation implementations.