To achieve the aims Dr. Tai will work closely with Dr. Sun and Dr. Jia to design and develop a small, inexpensive, and easy-to-use stimulator for foot neuromodulation, and test its safety and usability in 5 healthy subjects for a 2-week period. . The straps in the design have three functions: 1) making an electrical connection to electrode, 2) securing the insole and the electronic unit, and 3) facilitating observation and hand access to the top panel for adjusting the stimulation strength.