NIST OWM Info Hour: A Primary Lab in Every State? How Groundbreaking Kibble Balance Technology Will Revolutionize the Mass Calibration Laboratory

On May 1, 2025, the OWM Laboratory Metrology Program welcomed special guest speaker, Leon Chao, NIST Scientific Engineer from the Fundamental Electrical Measurements Group within the Physical Measurement Laboratory.   

Leon shared how this new groundbreaking technology can directly realize mass traceable to the revised SI through electrical measurements, putting the power of a primary mass standard directly into the hands of state and calibrations labs. 

OWM Info Hours: Revolutionizing Mass Calibrations with the Tabletop Kibble Balance

During this Info Hour, Leon:

• Described the fundamentals of a Kibble Balance and how state-of-the-art advancements will enable technological commercialization and modernization at the regulatory level (e.g., state laboratory metrology programs) for attaining SI traceability through a constant of nature (Planck’s constant). 
• Explained why traceability in measurements is critically important, and what the future holds for the traceability of mass calibrations.
• Discussed NIST’s efforts to miniaturize this technology for any lab’s implementation.  
• Shared current and ongoing collaborations with commercial partners, the Department of Defense, the “NIST on a Chip” Program, and the timetables for deliverables.

Additional links

• How We're Redefining the kg (Veritasium): https://www.youtube.com/watch?v=Oo0jm1PPRuo
• The Last Artifact (PBS): https://www.pbs.org/video/the-last-artifact-bvn9ea/
• Redefining the Kilogram (Science Friday, NPR): https://www.sciencefriday.com/segments/redefining-the-kilogram/

About our Guest Speaker

Leon Chao (B.S., M.S. Mech. Engr, University of Maryland) began his career as a precision design engineer for the NIST-4 Kibble Balance in 2012 aimed at measuring a value of the Planck constant to 8-digit accuracy. This machine ultimately contributed to the global effort in redefining the SI unit of mass, the kilogram, in terms of a fixed value of the Planck constant, sparking the complete revision of the SI. During these efforts, Leon spearheaded an outreach project to build and publish scientific data generated by a fun, LEGO-based tabletop Kibble balance with 1% accuracy, ultimately evolving into a full-blown endeavor to develop multiple generations of laboratory-grade tabletop balances with parts in 10⁶ accuracy alongside collaborations with the US Army, NIST-On-A-Chip (NOAC) program, and commercial partners.