A longwall mining system includes at least one face end roof support having a longitudinal length, and at least one near end roof support adjacent the face end roof support. The microneedle devices permit drug delivery or removal of body fluids at clinically relevant rates across skin or other tissue barriers, with minimal or no damage, pain, or irritation to the tissue. The negative time flux fields are next picked up by antennae of conductor which are connected to driver circuits to introduce a current pulse to the next arc.