Like most people, you have probably lost count of the number of perfectly pristine-looking shoes you have tossed out simply because the rubber soles are cracked. In addition to the expense and hassle of replacing footwear, it is also harmful to our environment. According to the U.S. Department of the Interior, 300 million pairs of shoes end up in landfills each year, where they can take 30 to 40 years to decompose. Now, thanks to a revolutionary self-healing 3-D printed rubber material, fractured shoe soles may be a thing of the past.