The Challenge of Manufacturing Between Macro and Micro
Classic ways of folding paper into dynamic shapes—origami, pop-up books—inspire methods to engineer millimeter-scale machines.
Building a complex consumer product like a smartphone involves solving a lot of different engineering challenges. One of the most difficult yet unappreciated is the challenge of scale. A smartphone contains components with sizes ranging from centimeters (the case and screen) to submillimeter (the accelerometer parts that tell the phone which way it is pointing) to submicrometer (the transistors in the processor). Each length requires a different set of materials and a distinctive set of assembly techniques. The final “nuts-and-bolts” creation of the complete phone is possible only after solving the whole set of scale-related challenges.
The large-scale design is what consumers notice most about the finished product and the microelectronics tend to get the most attention in technological discussions. But methods for building things at intermediate scales are actually the least developed. For reasons based on both physics and practicality, techniques used in macro-scale machining and assembly are inappropriate for complex devices with millimeter-scale features. On the other hand, integrated circuit-derived approaches are too limiting in terms of geometry and material choices to create a diversity of millimeter-scale machines. This size range, with features between tens of micrometers to tens of centimeters, is called the meso-scale.
My colleagues and I are developing novel techniques that could allow more flexible and more efficient manufacturing at those intermediate dimensions. One of the most promising directions is a process that sprang from a surprising inspiration: children’s pop-up books. We use some creative techniques to keep all the pieces in these devices aligned during manufacturing, and we employ some intricate joints and scaffolding to automatically fold flat designs into complex geometries.