Investigating the behavior of cardiomyocytes is an important part of drug development. We present a structure and a related nanoimprint-based fabrication method, where the cardiomyocytes form isolated fibers, which is beneficial for drug testing, more closely representing the structure of the cardiomyocytes in vivo. We found that channel structures with walls with a rough top surface stimulate cardiomyocytes to form such fibers, as desired. Nanoimprint lithography is used as a fast and cost-efficient method to fabricate our hierarchically structured cell growth substrates.