1、Designation: F2791 09F2791 14Standard Guide forAssessment of Surface Texture of Non-Porous Biomaterialsin Two Dimensions1This standard is issued under the fixed designation F2791; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes some of the more common methods that are available for measuring the topographical featu
3、res of asurface and provides an overview of the parameters that are used to quantify them. Being able to reliably derive a set of parametersthat describe the texture of biomaterial surfaces is a key aspect in the manufacture of safe and effective implantable medical devicesthat have the potential to
4、 trigger an adverse biological reaction in situ.1.2 This guide is not intended to apply to porous structures with average pore dimensions in excess of approximately 50 nm(0.05 m).1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this stan
5、dard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Reference
6、d Documents2.1 ASTM Standards:2C813 Test Method for Hydrophobic Contamination on Glass by Contact Angle MeasurementF2312 Terminology Relating to Tissue Engineered Medical ProductsF2450 Guide for Assessing Microstructure of Polymeric Scaffolds for Use in Tissue-Engineered Medical ProductsF2664 Guide
7、for Assessing the Attachment of Cells to Biomaterial Surfaces by Physical Methods2.2 Other Standards:3ISO 3274 Geometrical Product Specifications (GPS)Surface Texture: Profile MethodNominal Characteristics of Contact(Stylus) InstrumentsISO 4287 Geometrical Product Specifications (GPS)Surface Texture
8、: Profile MethodTerms, Definitions and SurfaceTexture ParametersISO 4288 Geometrical Product Specifications (GPS)Surface Texture: Profile MethodRules and Procedures for theAssessment of Surface TextureISO 135651 Geometrical Product Specifications (GPS)Surface Texture: Profile MethodSurfaces Having S
9、tratifiedFunctional Properties; Filtering and General Measurement Conditions3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 biocompatible, adja material may be considered biocompatible if the materials perform with an appropriate hostresponse in a specific application. F23123.
10、1.1 biomaterial, nany substance (other than a drug), synthetic or natural, that can be used as a system or part of a systemthat treats, augments, or replaces any tissue, organ, or function of the body. F26641 This guide is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Material
11、s and Devices and is the direct responsibility of Subcommittee F04.42on Biomaterials and Biomolecules for TEMPs.Current edition approved Aug. 1, 2009Oct. 1, 2014. Published September 2009December 2014. Originally approved in 2009. Last previous edition approved in 2009 asF279109. DOI: 10.1520/F2791-
12、09.10.1520/F2791-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standa
13、rds Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible t
14、o adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
15、shohocken, PA 19428-2959. United States13.1.2 evaluation length, ln, nlength in the direction of the x-axis used to assess the profile under evaluation.3.1.2.1 DiscussionThe evaluation length may contain one or more sampling lengths. ISO 42873.1.3 hydrophilic, adjhaving a strong affinity for water;
16、wettable.3.1.3.1 DiscussionHydrophilic surfaces exhibit zero contact angles. C8133.1.4 hydrophobic, adjhaving little affinity for water; nonwettable.3.1.4.1 DiscussionHydrophobic surfaces exhibit contact angles appreciably greater than zero: generally greater than 45 for the advancing angle.C8133.1.
17、5 implant, na substance or object that is put in the body as a prosthesis, or for treatment or diagnosis. F26643.1.6 lay, nthe direction of the predominant surface pattern. ISO 1356513.1.7 primary profile, nthe profile after application of the short wavelength filters. ISO 32743.1.8 profile peak, na
18、n outwardly directed (from the material to the surrounding medium) portion of the assessed profileconnecting two adjacent points of the intersection of the profile with the x-axis. ISO 42873.1.9 profile valley, nan inwardly directed (from surrounding medium to material) portion of the assessed profi
19、le connectingtwo adjacent points of the intersection of the assessed profile with the x-axis. ISO 42873.1.10 real surface, nsurface limiting the body and separating it from the surrounding medium. ISO 42873.1.11 sampling length, lr, n length in the direction of the x-axis used for identifying the ir
20、regularities characterizing the profileunder evaluation. ISO 42873.1.12 scaffold, na support, delivery vehicle or metric for facilitating the migration, binding, or transport of cells or bioactivemolecules used to replace, repair, or regenerate tissues. F24503.1.13 surface profile, nprofile that res
21、ults from the intersection of the real surface by a specified plane.3.1.13.1 DiscussionIn practice, it is usual to choose a plane with a normal that nominally lies parallel to the real surface and in a suitable direction.ISO 4287NOTE 1The surface shown in (A) has no directionality or lay, therefore
22、profiles can be oriented at any angle. Profiles (dashed line arrow) are drawnperpendicular to the lay (solid line arrow) in surfaces that have directionality (B).FIG. 1 Profile Orientation and Surface FeaturesF2791 1424. Significance and Use4.1 The term “surface texture” is used to describe the loca
23、l deviations of a surface from an ideal shape. Surface texture usuallyconsists of long wavelength repetitive features that occur as results of chatter, vibration, or heat treatments during the manufactureof implants. Short wavelength features superimposed on the long wavelength features of the surfa
24、ce, which arise from polishingor etching of the implant, are referred to as roughness.4.2 This guide provides an overview of techniques that are available for measuring the surface in terms of Cartesian coordinatesand the parameters used to describe surface texture. It is important to appreciate tha
25、t it is not possible to measure surface textureper se, but to derive values for parameters that can be used to describe it.5. The Relationship Between Surface Texture, Surface Chemistry, Surface Energy, and Biocompatibility5.1 The biocompatibility of materials is influenced by many factors such as s
26、ize, shape, material bulk, and surface chemicalcomposition, surface energy, and surface topography. Changing any one of these related characteristics of a biocompatible materialcan have a significant effect on cell behavior. The response of a cell to a biomaterial can be assessed by measuring the ad
27、hesivestrength between it and the underlying surface, monitoring changes in its shape or in the expression of biomarkers.5.2 The chemical species present on a surface can be mapped in detail using surface sensitive analysis techniques (for example,X-ray photoelectron spectroscopy where the penetrati
28、on depth is 10 nm or below (1).4 The chemical species present on the surfacetogether with the surface topography determine how hydrophilic the surface is. Measuring the contact angle between the surfaceand a fluid, usually water, can assess the degree of hydrophilicity of a surface. Care should be t
29、aken when comparing contact anglemeasurements made on different surfaces, as the relative contributions from the surface chemistry and texture are unlikely to bethe same.6. Surfaces and Surface Profiles6.1 Conventionally surfaces are described in Cartesian coordinates where the x-axis is defined as
30、being perpendicular to the laydirection. The y-axis is in plane in-plane and is perpendicular to the x-axis direction. The z-axis is out of plane. The profile of asurface that has a uniform, non-directional texture can be measured at any in plane in-plane orientation (see Fig. 1(A); however,several
31、profiles at different orientations should be measured to find the maximum amplitude (see Fig. 1(A). For patterned surfacesthat have periodic features, a lay, the orientation of the profile is at right angles to it (see Fig. 1(B).6.2 The measured surface is composed of three components: form, wavines
32、s and roughness. The form corresponds to theunderlying shape and tilt of the surface with respect to the measuring platform. The software packages used for surface textureanalysis all have a methodology for removing the form from the surface. The “corrected” surface can then be used to obtain a 2-Dp
33、rofile that describes the surface texture. This profile after removal of form is defined according to ISO 3274 as the primary profile.The stages involved in the analysis of the measured profile through primary profile to the roughness profile are shown in Fig. 2.7. Filtering and the Cut-Off Waveleng
34、th7.1 Surface data can be filtered to remove unwanted noise or to remove texture information at unwanted wavelengths. Filtersare classified according to the spatial periodicity that they allow to pass through; low-pass filters admit long wavelengths and rejectshort ones; high-pass filters do the opp
35、osite. Band-pass filters, as the name implies, allow a limited range of wavelengths to pass.In practice, using filters can create problems in deciding how much of the noise in the measurements is “real” and how much canbe attributed to the surface. It should be noted that some aspects of the surface
36、 are not faithfully reproduced due to limitations ofthe measurement method, for example, an inability to track the sides of steep valleys that is in essence a form of filtering. Thistopic is further discussed in Section 11.7.2 Filters used in surface texture measurements do not have a sharp cut-off
37、in spatial frequency above or below whichinformation is rejected. This gradual attenuation of high or low spatial frequency data helps avoid distortion of the measurementsthat can occur when strong features are close to the filtration limits. The point on the transmission curve at which the transmit
38、tedsignal is reduced to 50 % is referred to as the cut-off wavelength, c, of the filter, filter (Fig. 3.). For measurements made usinga stylus instrument (Section 11), the choice of c depends on the sampling frequency and the speed at which the stylus moves overthe surface. For example, measurements
39、 made at intervals of 0.01 mm from a device moving at 1 mms1 will generate data at afrequency of 100 Hz. Increasing the sampling interval to 0.1 mm will reduce the frequency at which data are obtained to 10 Hz.A high-pass filter that suppresses all frequencies below 10 Hz effectively removes any sur
40、face irregularities larger than 0.1 mmspacing from the data. Hence, filters can be used to bias the experimental data towards detecting profile (surface texture afterapplying a low-pass to filter the data), waviness (after applying a band-pass filter), and roughness (after applying a high-pass filte
41、r).Measurement conditions are set for filters according to the respective values of the sampling interval, measurement speed, andfiltration limits, according to ISO 3274.4 The boldface numbers in parentheses refer to a list of references at the end of this standard.F2791 1437.3 ISO 4287 specifies th
42、at 2-D roughness parameters need to be determined over five sequential sampling lengths, lr, unlessotherwise specified. This grouping of five serial sampling lengths is referred to as the evaluation length, ln. The sampling lengthvaries according to the length scale of the texture being assessed; la
43、rger features require a long sampling length. Guidance as towhich sampling length to use for a given range of feature sizes is shown in Table 1. It may be necessary to perform one or moreFIG. 2 Summary of Stages Involved in Analysis of Measured Profile to Obtain a Roughness ProfileFIG. 3 50 % Reduct
44、ion in Transmission CurveF2791 144iterations to identify the best value for lr. This can be achieved by calculating the mean width of a profile element, RSm (see Fig.4), from a measured profile where the value for lr is based on a best guess. This initial iteration will enable a new value for RSmto
45、be determined and that leads to a potential revision of lr according to Table 1.8. Quantification of Surface Profiles8.1 Parameters that are used to characterize 2-D surface profiles are grouped as:8.1.1 Amplitude parameters, which are measures of variations in profile height. These parameters are s
46、plit into two subclasses:averaging parameters, and peak and valley parameters;8.1.2 Spatial parameters, which describe in-plane variations of surface texture; and8.1.3 Hybrid parameters, which combine both amplitude and spatial information, forinformation (for example, meanslope.slope).8.2 RaThe mos
47、t widely used parameter to quantify surface texture is the arithmetical mean deviation of the absolute ordinatevalues, Z(x), of the profile from a center line (see Table 2 and Fig. 5). Despite its common usage, Ra does not provide a trulyaccurate representation of a surface profile since any informa
48、tion regarding peak heights or valley depths can be lost in itsderivation. This insensitivity to surface texture is apparent in Fig. 6, which shows that quite different profiles can have the sameRa value. The statistical significance of Ra is improved by averaging the values obtained for each of the
49、 five sampling lengths.TABLE 1 Guide to Choosing Sampling Lengths for theMeasurement of Periodic ProfilesNOTE 1Based on ISO 4288. The evaluation length is usually taken tobe five times the sampling length.Mean profile elementwidth, RSm (m)Sampling length,lr (m)13 RSm # 40 8040 RSm # 130 250130 RSm # 400 800400 RSm # 1300 25001300 RSm # 4000 8000TABLE 1 Guide to Choosing Sampling Lengths for theMeasurement of Periodic ProfilesAMean profile elementwidth, RSm (m)Sampling length,lr (m)13 RSm # 40 8040 RSm # 130 250130 RSm # 400 800400 RS
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