Systems and methods for treating internal tissue defects, such as septal defects, with clip-based devices are provided. An elongate first sheath has a distal end portion having melt bonding material. A sensor can be used to detect contaminant particles in the pattern. The first plurality of shafts form a first disc screen disposed in a first plane and the second plurality of shafts form a second disc screen at least a portion of which is disposed in a second plane.