Julie Sygiel, 27, USA

Julie Sygiel has used her chemical engineering background to develop a patent-pending fabric for underwear, which helps protect against menstruation and minor incontinence leaks.

Dear Kate specialises in high-performance underwear in a range of different styles and colours.

Her advice: "Keep going even when it's tough. Make yourself do the most important things first, even if they are scary, and ask for help from successful people you admire. You'll be surprised at how many times they respond and say yes."

You can find our 30 entrepreneurs talking about their experiences in under 30 seconds each on our 30under30 .