Abstract
Neutron reflectometry is a technique for measuring structure near planar interfaces that has been previously used to non-destructively characterize the polymer density of hydrated, dilute, and soft materials. Previous investigations have conducted neutron reflectometry measurements of liquids, gels, emulsion, and polymer solutions at rest, in compression, and subject to shear stress. However, correlating structure with tribological properties of soft materials presents significant experimental challenges for prior instruments due to wall slip, sample thickness, and structural heterogeneity (e.g., depth-wise gradients). A linear reciprocating tribometer offers several advantages for in situ neutron reflectometry studies, including uniform velocity profiles, constant shear stress over large regions of interest, and independent control of normal force and sliding velocity during measurements. This work outlines basic considerations for the design of a custom linear reciprocating tribometer that operates in a neutron beamline and includes commissioning measurements. The tribometer is designed to compress soft and hydrated materials against linearly reciprocating silicon disks. The three key design considerations for this tribometer are (1) safety, (2) neutron transmission, and (3) sample positioning. This instrument design will enable in situ studies of soft matter and illuminate the role of interfacial structure on tribological phenomena.
| Original language | English |
|---|---|
| Article number | 112 |
| Journal | Tribology Letters |
| Volume | 73 |
| Issue number | 3 |
| DOIs | |
| State | Published - Sep 2025 |
Funding
The authors gratefully acknowledge Dr. John Katsaras, Dr. Jim Browning, Candice Halbert, Dr. Helen Maynard-Casely, Dr. Anton Le Brun, Prof. Fyl Pincus, Prof. Matthew E. Helgeson, as well as the current and former members of the Interfacial Engineering Laboratory at UC Santa Barbara for helpful discussions. This work was primarily supported by the U.S. Department of Energy, Office of Science, Basic Energy Science, Neutron Scattering and Instrumentation Sciences under Award # DE-SC0024149. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to the liquids reflectometer (LIQREF, BL-4B) on proposal number IPTS-34380.1. We gratefully acknowledge the UC Santa Barbara Pitenis Faculty Seed account for supporting instrument development. K.E.S. gratefully acknowledges funding support from the U.S. Department of Education GAANN fellowship. B.L.B., J.J.O., and A.A.P. gratefully acknowledge funding support from Award # DE-SC0024149. A.A.K. acknowledges funding support from the California Institute for Regenerative Medicine (Grant # EDUC4-12821) and training support from the National Institutes of Health, USA (NIH grant 1T32GM141846). A.R.R. acknowledges support from the NSF Graduate Research Fellowship Program under Grant # 2139319. J.M.U. acknowledges funding support from the BioPACIFIC Materials Innovation Platform of the National Science Foundation under Award # DMR-1933487. This article was funded by U.S. Department of Education, GAANN, U.S. Department of Energy, Office of Science, Basic Energy Science, Neutron Scattering and Instrumentation Sciences, DE-SC0024149, DE-SC0024149, DE-SC0024149, California Institute for Regenerative Medicine, EDUC4-12821, NIH T32 Training Grant in Quantitative Mechanobiology, Award #1T32GM141846, National Science Foundation Graduate Research Fellowship Program, 2139319, BioPACIFIC Materials Innovation Platform of the National Science Foundation, DMR-1933487.
Keywords
- Neutron reflectometry
- Soft matter
- Tribometer design