One implementation provides a method for providing a solution to a problem durring an interaction. A felt sheet is disposed on the felt-mounting member, and has a front end snugly inserted into the insertion recess of the cap, and a rear end section received in the retaining recess in the handgrip. A fluid coupling has a thread at an inner periphery received on the thread on the nipple, and the coupling has a plurality of circumferentially spaced fingers spaced by grooves, with the fingers being snapped into the ditch and is biased against the ramped surface. The above method can be repeated one or more times for the other fluidic openings in the microfluidic device to determine whether there is a fault in any one or more microscale elements of the device. A lighting device using the method is also provided. Because the toner sealing member is not damaged by the repeated mounting and demounting of the toner cartridge, toner is supplied efficiently from the toner cartridge, without leaking towards the guide frame.