After testing various liquids, the researchers chose a metal alloy called Galinstan. Used in thermometers, it is similar to mercury but not poisonous.

在測試過不同的流體后，研究人員選擇了一種名為Galinstan的合金。將其注射進溫度計后，研究人員發現它與水銀很相似，不過沒有毒性。

Two small pouches, placed in the bottom of a shoe, are filled with the fluid and generate a current whenever they are compressed by the foot's up and down motion.

當他們將兩個裝有該流體的小袋子置于鞋內時，它們就會因人腳抬升和下落的動作而受到擠壓，從而產生電流。

Transferring the energy from a device in a foot to a phone in the hand presents an obvious hurdle.

而如何將裝置內的能量從腳部傳輸給手上的手機明顯就成了難題。

Rather than plugging a cable into a shoe, the Wisconsin researchers suggest installing a wireless transmitter in the heel. This could make radio contact with mobile phone base stations.

威斯康星的研究人員用安裝在腳后跟的無線發射機取代了需要塞進鞋子里的數據線。這樣能量就可以與手機基站取得無線電聯系。

Professor Krupenkin said: "Humans were 'very powerful energy-producing machines' that could produce as much as a kilowatt of power while sprinting."

克魯本勤教授說：“人類是非常強大的‘能源生產器’，人在疾跑時可以產生上千瓦的電量。”