Dirt-cheap sensors will replace $10,000 instruments

Princeton Professor Marcus Hultmark and three Ph.D. students in his lab were testing — in water — a high-resolution temperature sensor that they had developed and used successfully for measurements in air.

But then-graduate student Clayton Byers saw that the sensor was delivering backwards results: warm registered as cold and vice versa. Disappointment led to discovery as the team realized they were measuring fluid velocity, which has long proven much more difficult to measure than temperature.

It turned out that their instrument determines flow velocity in a completely novel way. The team — Hultmark, Byers, Matt Fu, and Yuyang Fan — spent more than a year deciphering the mechanics of what they dubbed elastic filament velocimetry (EFV). They patented the technology and started a company to develop it into a widely available product.

Their sensors are extremely sensitive to small flow rates, and their simplicity makes the manufacturing very scalable and cost-efficient. Both attributes will allow for large-scale commercial and industrial applications including chemical manufacturing, refining, and pharmaceutical manufacturing and delivery. The research team is also working to adapt the technology for further uses such as administering medicine to patients in syringe-like devices when dosage control is critical.

To measure flow, EFV uses nanoscale ribbons, ultra-fine filaments that span across two anchoring points like a suspension bridge. The team initially worked with material that was 300 microns long, 2 to 3 microns wide, and 0.1 microns thick (so if 1,000 of these nanoribbons were stacked on top of each other, the pile would be the same height as a strand of hair). When a flowing fluid hits the nanoribbons, they stretch, and the stretching changes their electrical properties in a way that reveals the precise flow rate.