Augmented reality provides new possibilities to propose environments where the designers can take advantage of the physicality of the artifacts while keeping the versatility of digital environments. Mixed objects can therefore provide new media in the interactions between stakeholders. Besides, the increasing interest in user participation in early design phases is limited by the poor representations or the expensive mock ups to be provided in design meetings. Therefore, understanding the role of these mixed artifacts by analyzing and characterizing the interactions is crucial to the development of both design methods and environments. By focusing on multimodal interactions, we aim at providing new results in terms of the design process, in particular by studying the contribution of the gesture in collaborative product co-creativity sessions but also by understanding the role of these multiple interactions in an augmented reality environment.