Abstract: Under the trend of economic globalization, the intensification of market competition, the diversification of consumer demand, the advancement of production technology and the refinement of products make product innovation an inevitable choice for enterprises to survive and progress. Continuous development of new products is an effective strategy for modern enterprises to maintain competitive advantage and gain economic profits. With the rapid development of Internet finance, there are more and more researches on crowdfunding, which mainly focus on funding success, supporters’ decision-making, influencing factors of satisfaction and so on. Some scholars believe that in addition to being a low cost, low risk and efficient financing tool, crowdfunding can also provide valuable feedback and creativity to the project, and it’s of great significance for the development of small and micro enterprises. Based on the Internet platform, the information dissemination speed in crowdfunding is fast, the number of supporters is large and they are of different backgrounds, and products are usually in the pre-stage of mass production. The initiators can get product feedback and creativity in time through crowdfunding to realize product innovation further. There are literature which have studied the relationship between interaction, co-creation and innovation. They believe that interaction can drive the co-creation process, and co-creation can help achieve product innovation. Other scholars have found that consumer-enterprise communication and interaction promote co-creation, and co-creation has a positive effect on innovation. Actor interaction is defined as establishing dialogues, exchanging resources and generating learning. The theory of value co-creation holds that the value that formed in the production and consumption of goods or services is created by both producers and consumers. Product innovation is a process of developing new products that are significantly different from original products and can satisfy customers’ needs. It is a complete process from planning, designing, developing, testing to releasing, and can be divided into three dimensions: function innovation, form innovation and service innovation. 
In this paper, we research how to motivate product innovation through exploratory multi-case studies based on grounded theory using Nvivo software. In order to ensure the scientific nature of case selection, two-stage cases screening method is adopted and four enterprises are selected as study objects. The case enterprises have launched several similar technology projects on representative public crowdfunding platform and realized product innovation later. Considering the innovation cycle, their first project should be launched in more than one year away. In order to ensure the reliability and validity, this paper uses a variety of data collection methods and data sources to obtain first-hand and second-hand data according to the triangulation method. Then the grounded theory was applied in three steps: The first step, open coding. The data labeling, conceptualization and categorization of the main case are carried out to refine concepts. The second step, spindle coding. The analysis of logic relations of conditions, action/interaction strategies and results is conducted to figure out the relationship between category and category. The third step, selective coding. The main categories are compared with the existing theories, the core categories are identified and connected with other categories to complete the theoretical construction. In addition, the other three cases are coded and analyzed respectively, trying to support or modify the concepts, categories or the relationship between categories that have been refined, until the coding has reached a better theoretical saturation and validity.
The research finds that: (1) the three categories of "sponsor learning", "supporter learning" and "information interaction" constitute the content of the actor interaction. The initiators obtain knowledge through cognitive learning and experiential learning driven by demand for product development of improvement, project implementation and solution achievement; the supporters eliminate doubts and enhance understanding through observation learning and exchange learning driven by demand for comprehensive understanding of projects and products; the initiators publish plans and update trends, supporters feedback through online comments and the initiators responds back to complete information exchange on the platform. (2) The four categories of "co-planning", "co-designing", "co-testing" and "co-promoting" constitute the process of value co-creation closely related to product innovation. Co-planning is to announce the product originality by the initiators and the supporters give feedbacks and suggestions from their own needs to create and evaluate the originality together; Co-designing is to share suggestions and participate in product designing with the initiator to determine product design scheme; Co-testing is to test and comment the product by the supporters for the initiators to further optimize the products; And co-promoting is both the propaganda of initiator and the recommendations and sharing of the supporters. (3) The case enterprises have achieved function innovation, form innovation or service innovation by initiating crowdfunding. According to the suggestions, ideas and feedbacks of supporters, innovation on function, form or service of case enterprises have taken place in different degrees, forming a multi-dimensional product innovation portfolio. (4) Actor interaction promotes the process of value co-creation to achieve product innovation. On one hand, actor interaction can promote value co-creation. The realization of value co-creation requires actor interaction, which is the precondition and basis for participating in value co-creation. Actor interaction helps initiators to tap the needs of supporters, and helps supporters understand the positioning of initiators’ opinions on products, thus it enables both sides to invest resources in the process of value co-creation. On the other hand, value co-creation can stimulate product innovation. Value co-creation is a complete process including co-planning, co-designing, co-testing and co-promoting. It transforms the resources contained in the actor interaction into product innovation power, and stimulates the innovation of product function, form and service.
Based on the theory of value co-creation, this paper has identified the content of the actor interaction in crowdfunding, summarized the process of value co-creation in crowdfunding from the perspective of product innovation process, and analyzed how the actor interaction promotes value co-creation so as to stimulate product innovation. These theoretical explorations show that crowdfunding can promote product innovation, enrich the connotation of actor interaction and value co-creation, and open up a new perspective of crowdfunding research and tap new function of crowdfunding. This is not only helpful to fill the theoretical gap, but also has important practical guiding significance for small and micro enterprises which are especially short of innovation resources.

Key words:  product innovation, value co-creation, actor interaction, case study, grounded theory