A Materialize CSS developer designs and creates visually appealing, user-friendly websites and web applications using Materialize CSS, a responsive front-end framework based on Google's Material Design. They use this framework to implement interactive UI components, animations, transitions, and grid-based layouts. They ensure the designs are mobile-responsive and cross-browser compatible. The developer also collaborates with other team members to integrate backend functionalities with the front-end, debug issues, and optimize performance. They continuously update their knowledge of Materialize CSS and other related technologies to improve the user interface and enhance the user experience.