-- --- -- SI TRACEABILITY OF FORCE AT THE NANONEWTON LEVEL Sneaker David B. Newell National Institute of Standards and Technologyl Gaithersburg, MD 20899-8112 U.S.A. Phone: (301)975-4228 Fax: (301)975-2115 Email: david.newell@nist.gov Paper Authors D. B. Newell, 1. R. Pratt, 1. A. Kramar, D. T. Smith, L. A. Feeney, and E. R. Williams National Institute of Standards and Technology Gaithersburg, MD Abstract Although nanonewton force measurements are commonplace in industry, no National Measurement Institute supports a link to the International System ~f Units (SI) below one newton. The National Institute of Standards and Technology has launched a five-year inter- laboratory project focusing on the development of an instrument and laboratory capable of realizing and measuringthe SI unit of force below 5 micronewtonsusing the electrical units as the link to the SI. We will give a brief overview of this project, instrument performance objectivesand designs,and initialtrials with a prototypeelectrostaticforcebalance. Small Force Measurements Present Status The last decade produced a flurry of activity in the measurement of small forces. Materials scientists developed "instrumented indentation" as an indispensable tool for the study of micromechanical material pro~erties, such as hardness and modulus(l), and for fatigue and fracture testing of thin films(2.3. Forces produced by instrumented indentation machines often range between 10-8 Nand 10.2 N. Similarly, nanotechnology and biotechnology researchers adapted the Atomic Force Microscope (AFM) to quantitative force measurement, achieving 10-12 N resolution in studies ranging from the adhesion of ultrathin films(4)to the measurement of covalent bonds(S). I ElectricityDivision,ElectronicsandElectricalEngineeringLaboratory,TechnologyAdministration,U.S. Department of Commerce. Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States. 2001 NCSL International Workshop & Symposium