Sure, there are a ton of studies done on this, but here is my very unscientific personal take. When team members can make decisions about how they work on projects, they are more engaged and connected to the project outcome. When they see how potentially dropping the ball would affect the entire team, they step up. When they feel like what they are doing is impactful and valued, they are naturally motivated to learn more, and be even better team members.

Rarely does a one-size-fits-all style work when it comes to team motivation. I have found that aligning employee goals with organization goals works well. Taking time to get to know everyone on your team is invaluable. What parts of their job do they love? What do they not enjoy? What skills do they want to learn? Even going so far as to where they see themselves in five years career-wise. These questions help you right-fit projects, and help your team see you are committed to creating a career path for them within the company.

Most designers I know love a good challenge. We are problem solvers by nature. Consistently give yourself and your team small challenges, both design-related and not. It will promote openness within the team to collaborate, and it will help generate ideas faster in the long run. Whether the challenge is to find a more exciting way to present an idea to stakeholders or fitting a new tool into the budget, make it a challenge just to shake things up.