Currently, little work has been devoted to the mediators and tools for multi-role production interactions in the mass individualization environment. This paper proposes a kind of hardware-software-integrated mediators called social sensors(S~2 ensors) to facilitate the production interactions among customers, manufacturers, and other stakeholders in the social manufacturing systems(SMS).The concept, classification, operational logics, and formalization of S~2 ensors are clarified. S~2 ensors collect subjective data from physical sensors and objective data from sensory input in mobile Apps, merge them into meaningful information for decision-making, and finally feed the decisions back for reaction and execution. Then, an S~2 ensors-Cloud platform is discussed to integrate different S~2-ensors to work for SMSs in an autonomous way. A demonstrative case is studied by developing a prototype system and the results show that S~2 ensors and S~2 ensorsCloud platform can assist multi-role stakeholders interact and collaborate for the production tasks. It reveals the mediator-enabled mechanisms and methods for production interactions among stakeholders in SMS. Currently, little work has been devoted to the mediators and tools for multi-role production interactions in the mass individualization environment. This paper proposes a kind of hardware-software-integrated mediators called social sensors (S ~ 2 ensors) to facilitate the production of interactions among users, manufacturers, and other stakeholders in the social manufacturing systems (SMS). The concept, classification, operational logics, and formalization of S ~ 2 ensors are clarified. S ~ 2 ensors collect subjective data from physical sensors and objective data from sensory input in mobile Apps, merge them into meaningful information for decision-making, and finally feed the decisions back for reaction and execution. Then, an S ~ 2 ensors-Cloud platform is discussed to integrate different S ~ 2-ensors to work for SMSs in an autonomous way. A demonstrative case is studied by developing a prototype system and the results show that S ~ 2 ensors and S ~ 2 ensors Cloud platform can assist multi-role stake holders interact and collaborate for the production tasks. It reveals the mediator-enabled mechanisms and methods for production interactions amongst stakeholders in SMS.