Sibrecht Bouwstra, a student at the Technical University of Eindhoven, just published a project report describing custom Technic parts. Her project focused on two kinds of parts: flexible parts, which you can see in the top picture, and a motor (she wanted to make a silent, or more precisely very quiet, motor). The report describes several different methods of making flexible parts, and the picture above shows the most successful products. The motor unit includes a motor with internal gearing (using a worm gear).

Sibrecht’s web site includes a detailed illustrated project report and a movie showing the motor driving these flexible elements to create a fluid motion (click on Gallery then Lego).