In this paper we designed a STEM outreach program with a modular tissue engineering education tool (we refer to as "modular cyclic-stretch device") to engage high school students in STEM hands-on activities. Using simple machines such as gears and rotating cams, students were able to build a custom device to apply cyclic stretch to biomaterials. With the help of this hands-on activity, our outreach program helped students grasp tendon tissue biomechanics and understand the importance of applying biomechanical force to regenerate tendon tissue in a laboratory setting. The two-day outreach program comprised: (1) pre- and post-tests; (2) lectures; (3) laboratory sessions, including the microscopic examination of stained tissue sections and a hands-on group activity employing the modular cyclic-stretch device; and (4) homework. Assessment results suggest that our program supports improved student awareness and interest in tissue engineering as a future profession. The program elevated students' confidence in their ability to apply engineering principles to tasks such as building a modular cyclic-stretch device and measuring the mechanical properties of biological tissues. Building an educational bioreactor improved students' understanding of the dynamic nature of the human body and the importance of tissue engineering as an emerging discipline towards replacing or regenerating damaged organs. We propose that our modular device has great outreach potential to introduce tissue engineering concepts to high school and potentially college freshmen engineering students.