Talking to the customer is one part. However, understanding their needs for a product or solution that delivers value is paramount. I-Corp is a great way for academic teams to explore the business behind the science.
Doing the math, coding, and running experiments don’t always translate into business unless you clearly understand the problem, as well as the market. We seldom think of scientists as doing anything that is going to be of any immediate practical or transactional value in our daily lives. This is also the case with deep science-based start-ups. There are some money managers and investors who understand the long gestation period for some of these advanced scientific concepts to fructify into commercially viable products, there is little to no patient money at work with these start-ups.
I usually challenge deep science start-ups to take a hard look at the low hanging fruit, research, or IP that can be licensed immediately, such as a process, software, or code. This may also involve an existing solution, product, device, or simply a better method that a company can use or license for immediate use as long as there are no arduous regulatory challenges. One example would be a surgical device already on the market, yet your solution creates some type of efficiency.
All that said, it is essential to always talk to customers first to gain insight into the problem to be solved before you assume people actually want or need what you have been building.