A piggyback duffel apparatus and system provide a modular apparatus that expands a storage capacity of a backpack and includes a detachable piggyback duffel bag that may have a vertical strap to attach to loops on a side of the backpack. Also disclosed are polypeptides encoded by these nucleic acid sequences, and antibodies, which immunospecifically-bind to the polypeptide, as well as derivatives, variants, mutants, or fragments of the aforementioned polypeptide, polynucleotide, or antibody. Patterned pixel electrodes including intersected electrodes and stripe electrodes are formed on a second substrate. Thus, electrical energy in the form of heat generated by the flow of current is dissipated at least partially by the evaporative fluid.