Universities worldwide are developing and implementing Challenge Based Learning (CBL) as a new educational concept in Engineering Education (Gallagher & Savage, 2020). Here, students work on their own, highly open-ended projects that are aligned with current stakeholders and in line with the 'grand challenge' of today's society (van den Beemt et al., 2023). To do this successfully, it is crucial to develop best practices and support teachers in designing and implementing CBL.

AIMION is a tangible tool to support students in Challenge Based Learning teams in conceptualising their projects, setting their goals and developing reflective self-direction. The tangibility of the tool structures students' thinking, collaboration and reflection and makes these more visible (and accessable) to the teachers (or tutors) supervising the student teams. Finally, the tool stores information about students' decisions, making it easier for students to reflect on their team process and previous decisions.

This contribution describes how the AIMION tool was developed based on Veelenturf's initial design (2023) using an educational design methodology (Plomp & Nieveen, 2007) which comprised several rounds of (re)design and evaluative research.

The first test run was conducted within one of a CBL subjects at the Faculty of Mechanical Engineering (ME). Four student teams used the AIMION tool and were closely monitored. The evaluation study included classroom observations, interviews with students and teachers and analysis of the AIMION game boards. Date we triangulated (Denzin, 2012).

In parallel to this test, smaller pilots were conducted at other departments of the university and additional explorations were carried out (Diederen et al., 2024) (Kessels & Schellekens, 2024). All this underpinned the redesign of the AIMION tool and the guidelines for its use that were provided to teachers (tutors) and participating students.

The redesigned tool was carefully implemented in the same course in the Department of Mechanical Engineering in a second test run. This involved another four student teams using AIMION (experimental group), as well as four student teams working on their CBL projects in the usual way. This provided a basis for comparison (control group). The evaluation again consisted of the above data types, but now focused on the impact of the AIMION tool on the group process and outcomes of the four AIMION groups compared to those in the control groups.

Conclusions relate to the AIMION tool's contribution to students' self-direction and reflection. Students and tutors appreciate the tool for its tangibility, how it structures and deepens discussions, and how it creates opportunities to interact, exchange ideas and explore project options. Evaluation shows that the AIMION tool can significantly help deepen goal-setting and reflection, both at group and individual level.

The results also include several guidelines for further improving the AIMION tool and for its implementation in education. In particular, the importance of adequately tailoring the tool to the specific teaching context in which it will be used. For example, carefully embedding the use of the tool in the course's workflow and assessment system. And aligning the tool with the 'local teaching culture' of the course (e.g. aligning it with teachers' and students' views and expectations on the place of (self)reflection as an element within the professional practice of that subject).

Keywords: Challenge-based Learning (CBL), learning in projects, Engineering, student reflection, student self-direction, tangible, teacher support.