Potassium ions (K+) level in the human body is critical for the electrolyte balance of the body and the nerves and muscles functions. So it is very important to accurately and rapidly determine potassium concentrations in human fluids in clinical fields. This paper describes a novel concept for a potassium ion biosensor that accurately, rapidly, and efficiently monitors the presence and records the concentration of potassium ions with high specificity, not only in serum and urine, but also in the sweat or even eye fluid. This specific biosensor design utilizes a nanomanufacturing technique, i.e. electrospinning, to produce advanced nano-bio-composites that specifically trace even minute quantities of potassium ions through the use of selective bio-receptors (ionophores) attached to high surface area nanofibers. Electroactive polymers are then employed as transducers to produce an electronic (rather than ionic) output that changes instantly with the change in K+ concentration. A convenient, non-invasive, maintenance-free “Band-aid” type configuration of skin patch is demonstrated in this paper.