They designed a square sheet with 32 rigid tiles that are connected by 20 actuators/hinges to form a crease pattern. Actually, the pattern is the basic windmill base that was so important in the European side of paper folding! This pattern can make boats, planes, windmills, the Pajarita, horses, fish and such.
Windmill Base Crease Pattern
They used nitinol which is a metal that can be programmed, via an annealing (heating) process, to a specified shape. For example, if I bent it into a tube and clamped it so that it could not unbend, then annealed it, the tube shape would be locked into the nitinol's memory. When cool, the nitinol can be bend into a different shape, like a cup, but if it were to be heated up again, the nitinol would take on the memory shape, which in the example is a tube.
So anyway, the nitinol was given a memory shape of the hinge being closed, then it was bend open. Once the hinges are heated up, they will close, forcing the sheet to fold. The way they heated up the hinges is to run electricity through them, allowing the resistance of the nitinol to create the heat. This means that they could use electricity to close the creases, but would have to unfold them by hand.
If you want to know more about it, I suggest you read the article!