DOI: 10.5061/dryad.bg79cnpnz
title: Linear reciprocating tribometer for in situ neutron reflectometry of soft matter

description: 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 (eg., 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.
description: # Linear reciprocating tribometer for in situ neutron reflectometry of
 soft matter Dataset DOI:
 [10.5061/dryad.bg79cnpnz](10.5061/dryad.bg79cnpnz) ## Description of the
 data and file structure Data from peer-reviewed article: Title: Linear
 Reciprocating Tribometer for In Situ Neutron Reflectometry of Soft Matter
 DOI: [Insert link upon acceptance of publication] Authors: Kathryn E.
 Shaffer, Brendan Louie Bagorio, Ahmed Al Kindi, Julia J. Ong, Andrew R.
 Rhode, Erik B. Watkins, Rebecca J. L. Welbourn, Roger Pynn, Juan Manuel
 Urueña, and Angela A. Pitenis Corresponding Authors: Angela A. Pitenis
 apitenis@ucsb.edu ### Files and variables #### File:
 2025-07-17-TribLett-Shaffer-Data.zip **Description:**  File List: A)
 Fig3_AB_Force_Time.csv B) Fig3_C_Fn_Histogram.csv C)
 Fig3_D_Ff_Histogram.csv D) Fig4_B_Position1_Reflectivity_Q.csv E)
 Fig4_B_Position2_Reflectivity_Q.csv F) Fig4_B_Motion_Reflectivity_Q.csv G)
 Fig4_C_SLD.csv H) FigS5_AB_Force_Time.csv I) FigS5_C_Fn_Histogram.csv J)
 FigS5_D_Ff_Histogram.csv K) FigS6_MotionProfile.csv L)
 FigS7_MotionProfile.csv Figure 3: Load cell data A)
 Fig3_AB_Force_Time.csv: normal force and friction force data as a function
 of time recorded by the load cell for a sample holder moving in water but
 not in contact \* Row 1: labels for column data with units \* Column A:
 time, in seconds \* Column B: friction force, in newtons \* Column C:
 normal force, in newtons B) Fig3_C_Fn_Histogram.csv: histogram binning of
 normal force data for both the forward and reverse motion directions \*
 Row 1: labels for column data with units \* Column A: bin center normal
 force, in newtons \* Column B: forward frequency, in counts \* Column C:
 reverse frequency, in counts C) Fig3_D_Ff_Histogram.csv: histogram binning
 of friction force data for both the forward and reverse motion directions
 \* Row 1: labels for column data with units \* Column A: bin center
 friction force, in newtons \* Column B: forward frequency, in counts \*
 Column C: reverse frequency, in counts Figure 4: Neutron data D)
 Fig4_B_Position1_Reflectivity_Q.csv: reflectivity data and fits for
 position 1 \* Row 1: labels for column data with units \* Column A: Q
 vector, in inverse angstroms \* Column B: error in Q vector, in inverse
 angstroms \* Column C: reflectivity, in arbitrary units \* Column D: error
 in reflectivity, in arbitrary units \* Column E: reflectivity fit, in
 arbitrary units E) Fig4_B_Position2_Reflectivity_Q.csv: reflectivity data
 and fits for position 2 \* Row 1: labels for column data with units \*
 Column A: Q vector, in inverse angstroms \* Column B: error in Q vector,
 in inverse angstroms \* Column C: reflectivity, in arbitrary units \*
 Column D: error in reflectivity, in arbitrary units \* Column E:
 reflectivity fit, in arbitrary units F) Fig4_B_Motion_Reflectivity_Q.csv:
 reflectivity data and fits during motion at velocity=5 mm/s \* Row 1:
 labels for column data with units \* Column A: Q vector, in inverse
 angstroms \* Column B: error in Q vector, in inverse angstroms \* Column
 C: reflectivity, in arbitrary units \* Column D: error in reflectivity, in
 arbitrary units \* Column E: reflectivity fit, in arbitrary units G)
 Fig4_C_SLD.csv: scattering length density fitting parameters and
 confidence intervals \* Row 1: labels for column data \* Column A:
 parameter labels for scattering length density fits with units \* Column
 B: value of parameter, with units as indicated in column A \* Column C:
 parameter's lower value for a 68% confidence interval fit, with units
 as indicated in column A \* Column D: parameter's upper value for a
 68% confidence interval fit, with units as indicated in column A \* Column
 E: parameter's lower value for a 95% confidence interval fit, with
 units as indicated in column A \* Column F: parameter's upper value
 for a 95% confidence interval fit, with units as indicated in column A \*
 Row 2: neutron signal background for position 1, in arbitrary units \* Row
 3: position 1 neutron signal intensity, in arbitrary units \* Row 4:
 position 1 D2O scattering length density with units of multiplied by ten
 to the power of negative six angstroms squared \* Row 5: position 2
 neutron signal background, in arbitrary units \* Row 6: position 2 neutron
 signal intensity, in arbitrary units \* Row 7: position 2 D2O scattering
 length density with units of multiplied by ten to the power of negative
 six angstroms squared \* Row 8: reciprocating motion neutron signal
 background, in arbitrary units \* Row 9: reciprocating motion neutron
 signal intensity, in arbitrary units \* Row 10: reciprocating motion D2O
 SLD with units of multiplied by ten to the power of negative six angstroms
 squared \* Row 11: Si roughness, in angstroms \* Row 12: SiO2 interface
 roughness, in angstroms \* Row 13: SiO2 scattering length density with
 units of multiplied by ten to the power of negative six angstroms squared
 \* Row 14: SiO2 thickness, in angstroms \* Row 15: contaminant interface
 roughness, in angstroms \* Row 16: contaminant scattering length density
 with units of multiplied by ten to the power of negative six angstroms
 squared \* Row 17: contaminant thickness, in angstroms Supplementary
 Figure S5: Load cell data in an environmental enclosure H)
 FigS5_AB_Force_Time.csv: normal force and friction force data as a
 function of time recorded by the load cell for a sample holder moving in
 water but not in contact contained in an environmental enclosure \* Row 1:
 labels for column data with units \* Column A: time, in seconds \* Column
 B: friction force, in newtons \* Column C: normal force, in newtons I)
 FigS5_C_Fn_Histogram.csv: histogram binning of normal force data for both
 the forward and reverse motion directions \* Row 1: labels for column data
 with units \* Column A: bin center normal force, in newtons \* Column B:
 forward frequency, in counts \* Column C: reverse frequency, in counts J)
 FigS5_D_Ff_Histogram.csv: histogram binning of normal friction data for
 both the forward and reverse motion directions \* Row 1: labels for column
 data with units \* Column A: bin center friction force, in newtons \*
 Column B: forward frequency, in counts \* Column C: reverse frequency, in
 counts Supplementary Figure S6: motion profiles for the tribometer x
 stage, XT-stage for multiple cycles K) FigS6_MotionProfile.csv: position,
 velocity and acceleration with respect to time \* Row 1: labels for column
 data with units \* Column A: time, in seconds \* Column B: position, in
 millimeters \* Column C: velocity, in millimeters per second \* Column D:
 acceleration, in millimeters per second squared Supplementary Figure S7:
 motion profiles for the tribometer x stage, XT-stage for one turnaround
 region L) FigS7_MotionProfile.csv: position, velocity and acceleration
 with respect to time \* Row 1: labels for column data with units \* Column
 A: time, in seconds \* Column B: position, in millimeters \* Column C:
 velocity, in millimeters per second \* Column D: acceleration, in
 millimeters per second squared