Biological and Medical Physics, Biomedical Engineering Bharat Bhushan Biophysics of Skin and Its Treatments Structural, Nanotribological, and Nanomechanical Studies Biophysics of Skin and Its Treatments More information about this series at http://www.springer.com/series/3740 BIOLOGICAL AND MEDICAL PHYSICS, BIOMEDICAL ENGINEERING Thefieldsofbiologicalandmedicalphysicsandbiomedicalengineeringarebroad,multidisciplinaryanddynamic. Theylieatthecrossroadsoffrontierresearchinphysics,biology,chemistry,andmedicine.TheBiologicaland MedicalPhysics,BiomedicalEngineeringSeriesisintendedtobecomprehensive,coveringabroadrangeoftopics importanttothestudyofthephysical,chemicalandbiologicalsciences.Itsgoalistoprovidescientistsand engineerswithtextbooks,monographs,andreferenceworkstoaddressthegrowingneedforinformation. Booksintheseriesemphasizeestablishedandemergentareasofscienceincludingmolecular,membrane,and mathematicalbiophysics;photosyntheticenergyharvestingandconversion;informationprocessing;physical principlesofgenetics;sensorycommunications;automatanetworks,neuralnetworks,andcellularautomata. Equallyimportantwillbecoverageofappliedaspectsofbiologicalandmedicalphysicsandbiomedicalengi- neeringsuchasmolecularelectroniccomponentsanddevices,biosensors,medicine,imaging,physicalprinciples ofrenewableenergyproduction,advancedprostheses,andenvironmentalcontrolandengineering. Editor-in-Chief: EliasGreenbaum,OakRidgeNationalLaboratory,OakRidge,Tennessee,USA EditorialBoard: PierreJoliot,InstitutedeBiologie MasuoAizawa,DepartmentofBioengineering, TokyoInstituteofTechnology,Yokohama,Japan Physico-Chimique,FondationEdmond deRothschild,Paris,France OlafS.Andersen,DepartmentofPhysiology, BiophysicsandMolecularMedicine, LajosKeszthelyi,InstituteofBiophysics,Hungarian CornellUniversity,NewYork,USA AcademyofSciences,Szeged,Hungary PaulW.King,BiosciencesCenterandPhotobiology RobertH.Austin,DepartmentofPhysics, Group,NationalRenewableEnergyLaboratory, PrincetonUniversity,Princeton,NewJersey,USA Golden,Colorado,USA JamesBarber,DepartmentofBiochemistry, RobertS.Knox,DepartmentofPhysics ImperialCollegeofScience,Technology andAstronomy,UniversityofRochester,Rochester, andMedicine,London,England NewYork,USA HowardC.Berg,DepartmentofMolecular AaronLewis,DepartmentofAppliedPhysics, andCellularBiology,HarvardUniversity, HebrewUniversity,Jerusalem,Israel Cambridge,Massachusetts,USA StuartM.Lindsay,DepartmentofPhysics VictorBloomfield,DepartmentofBiochemistry, andAstronomy,ArizonaStateUniversity, UniversityofMinnesota,St.Paul,Minnesota,USA Tempe,Arizona,USA RobertCallender,DepartmentofBiochemistry, DavidMauzerall,RockefellerUniversity, AlbertEinsteinCollegeofMedicine, NewYork,NewYork,USA Bronx,NewYork,USA EugenieV.Mielczarek,DepartmentofPhysics StevenChu,LawrenceBerkeleyNational andAstronomy,GeorgeMasonUniversity,Fairfax, Laboratory,Berkeley,California,USA Virginia,USA LouisJ.DeFelice,DepartmentofPharmacology, MarkolfNiemz,MedicalFacultyMannheim, VanderbiltUniversity,Nashville,Tennessee,USA UniversityofHeidelberg,Mannheim,Germany JohannDeisenhofer,HowardHughesMedical V.AdrianParsegian,PhysicalScienceLaboratory, Institute,TheUniversityofTexas,Dallas, NationalInstitutesofHealth,Bethesda, Texas,USA Maryland,USA GeorgeFeher,DepartmentofPhysics, LindaS.Powers,UniversityofArizona, UniversityofCalifornia,SanDiego,LaJolla, Tucson,Arizona,USA California,USA EarlW.Prohofsky,DepartmentofPhysics, HansFrauenfelder, PurdueUniversity,WestLafayette,Indiana,USA LosAlamosNationalLaboratory, TatianaK.Rostovtseva LosAlamos,NewMexico,USA NICHD,NationalInstitutesofHealth, IvarGiaever,RensselaerPolytechnicInstitute, Bethesda,Maryland,USA Troy,NewYork,USA AndrewRubin,DepartmentofBiophysics,Moscow SolM.Gruner,CornellUniversity, StateUniversity,Moscow,Russia Ithaca,NewYork,USA MichaelSeibert,NationalRenewableEnergy JudithHerzfeld,DepartmentofChemistry, Laboratory,Golden,Colorado,USA BrandeisUniversity,Waltham,Massachusetts,USA DavidThomas,DepartmentofBiochemistry, MarkS.Humayun,DohenyEyeInstitute, UniversityofMinnesotaMedicalSchool, LosAngeles,California,USA Minneapolis,Minnesota,USA Bharat Bhushan Biophysics of Skin and Its Treatments Structural, Nanotribological, and Nanomechanical Studies 123 BharatBhushan NanoprobeLaboratory for Bio- & Nanotechnology andBiomimetics TheOhio State University Columbus, OH USA ISSN 1618-7210 ISSN 2197-5647 (electronic) Biological andMedical Physics, Biomedical Engineering ISBN978-3-319-45706-2 ISBN978-3-319-45708-6 (eBook) DOI 10.1007/978-3-319-45708-6 LibraryofCongressControlNumber:2016949581 ©SpringerInternationalPublishingSwitzerland2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinor foranyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland To my grandkids Sahana, Ashwin, and Joya Preface Skinistheouterlayercoveringhumanoranimalbodyandisacomplexbiological structure. Its function is to protect the body from physical and environmental assaults and to provide sensation, heat regulation, water resistance, and so on. Environmental conditions, such as dry and cold weather, can reduce the moisture content of skin and increase the skin roughness and physical discomfort. Skin is damaged as it goes through daily activities. Skin also ages with time. For healthy and beautiful human skin, cleaning and maintenance of skin is a daily process. Various beauty care products involve surface interaction between the product and the skin surface they are applied to. Skin cream is used to improve the skin health andcreateasmooth,soft,andflexiblesurfacewithmoistperceptionbyalteringthe surface roughness, adhesion, friction, elasticity, and surface charge of the skin surface.Rheologyofskincreamasafunctionofcreamthicknessandstrainrateand the binding interaction between skin cream and skin surface and operating envi- ronmentaresomeoftheimportantfactorsaffectingthesmoothfeelandrepairofthe skin surface. The vibrations generated during the rubbing are a function offriction at the interface and govern the tactile perception of skin texture by the brain. Atomic force microscopy (AFM) and nanoindentation have recently become important tools for studying micro-/nanoscale properties in beauty care, including human hair, hair conditioner, skin, and skin cream. In this book, we present an overviewofthestructural,nanotribological,andnanomechanicalpropertiesofskin withandwithoutcreamtreatmentasafunctionofoperatingenvironment.Relevant mechanismsarediscussed.Theresultofatriboelectrificationstudyofskinwithand without cream treatment is presented. Next, an overview of attempts to develop a syntheticskinforresearchpurposesispresented.Finally,dataontactileresponseof skin with and without cream treatment are presented. Thisisthefirstbookonnanotribologicalandnanomechanicalpropertiesofskin andskintreatment.Thebookiswrittenforanoviceinthefield.Itshouldserveasa reference book for researchers, practitioners, and users. vii viii Preface The author would like to thank his former students and senior colleagues who contributed to the research reported in the book. These include Prof. Shirong Ge, Dr.WeiTang,Dr.SiChen,andShuyangDing.Theauthorwouldalsoliketothank Renee L. Ripley for many important contributions during the preparation of the manuscript. Powel, OH, USA Bharat Bhushan Contents 1 Introduction... .... .... ..... .... .... .... .... .... ..... .... 1 1.1 Tribological and Mechanical Properties and Triboelectric Effects.... .... .... ..... .... .... .... .... .... ..... .... 2 1.2 Tactile Perception... ..... .... .... .... .... .... ..... .... 4 1.3 Application of Skin Cream, Tactile Perception, and Role of Tribology .... .... .... .... .... .... ..... .... 5 1.4 Organization of the Book.. .... .... .... .... .... ..... .... 7 References. .... .... .... ..... .... .... .... .... .... ..... .... 7 2 Skin and Skin Cream ... ..... .... .... .... .... .... ..... .... 11 2.1 Skin . .... .... .... ..... .... .... .... .... .... ..... .... 11 2.2 Pig and Rat Skin ... ..... .... .... .... .... .... ..... .... 16 2.3 Skin Cream.... .... ..... .... .... .... .... .... ..... .... 16 2.4 Synthetic Skin for Cosmetics Science. .... .... .... ..... .... 19 References. .... .... .... ..... .... .... .... .... .... ..... .... 20 3 Experimental Techniques ..... .... .... .... .... .... ..... .... 25 3.1 Animal Skins and Skin Creams . .... .... .... .... ..... .... 25 3.1.1 Animal Skin . ..... .... .... .... .... .... ..... .... 25 3.1.2 Damaged Skin..... .... .... .... .... .... ..... .... 27 3.1.3 Various Skin Creams and Cream Treatment Procedure ... ..... .... .... .... .... .... ..... .... 27 3.2 Synthetic Skin Samples ... .... .... .... .... .... ..... .... 29 3.2.1 Synthetic Skin-1 ... .... .... .... .... .... ..... .... 29 3.2.2 Synthetic Skin-2 ... .... .... .... .... .... ..... .... 30 3.3 Physical Characterization .. .... .... .... .... .... ..... .... 31 3.3.1 Contact Angle Measurements . .... .... .... ..... .... 31 3.3.2 Dynamic Viscosity Measurements.. .... .... ..... .... 31 3.3.3 Nanoscale Surface Roughness, Friction, Adhesive Force, and Wear Resistance Measurements... ..... .... 32 3.3.4 Film Thickness, Adhesive Forces, and Young’s Modulus Mapping.. .... .... .... .... .... ..... .... 33 ix x Contents 3.3.5 Macroscale Friction and Wear Resistance (Durability) Measurements ... .... .... .... ..... .... 36 3.3.6 Nanomechanical Properties Measurements ... ..... .... 36 3.3.7 Surface Potential Measurements ... .... .... ..... .... 38 3.3.8 Humidity and Temperature Control. .... .... ..... .... 40 References. .... .... .... ..... .... .... .... .... .... ..... .... 40 Part I Rat Skin—Virgin 4 Adhesion, Friction, and Wear of Rat Skin With and Without a Common Cream Treatment.. .... ..... .... 47 4.1 A Common Cream Treatment... .... .... .... .... ..... .... 47 4.1.1 Surface Roughness and Friction on the Nanoscale .. .... 47 4.1.2 Effect of the Duration of Cream Treatment on Film Thickness and Effect of Cream Film Thickness, Velocity, and Normal Load on Adhesion and Friction on the Nanoscale. .... .... .... ..... .... 49 4.1.3 Effect of Relative Humidity and Temperature on Adhesion and Friction on the Nanoscale .. ..... .... 52 4.1.4 Wear Resistance on the Nanoscale . .... .... ..... .... 53 4.1.5 Effect of Cream Film Thickness, Velocity and Normal Load on Friction as Well as Wear Resistance on the Macroscale.. .... .... .... .... .... ..... .... 55 4.1.6 Summary.... ..... .... .... .... .... .... ..... .... 58 4.2 Various Cream Treatments. .... .... .... .... .... ..... .... 58 4.2.1 Duration of Cream Treatment, Adhesion, Friction, Dynamic Viscosity and Wear Resistance on the Nanoscale... .... .... .... .... .... ..... .... 59 4.2.2 Effect of Relative Humidity on Film Thickness, Adhesive Forces and Effective Young’s Modulus Mappings on the Nanoscale .. .... .... .... ..... .... 62 4.2.3 Summary.... ..... .... .... .... .... .... ..... .... 66 References. .... .... .... ..... .... .... .... .... .... ..... .... 66 5 Nanomechanical Properties of Rat Skin With and Without a Common Cream Treatment.. .... ..... .... 69 5.1 Nanoscratch ... .... ..... .... .... .... .... .... ..... .... 69 5.2 Nanoindentation .... ..... .... .... .... .... .... ..... .... 71 5.3 In Situ Tensile Measurements... .... .... .... .... ..... .... 72 5.4 Summary . .... .... ..... .... .... .... .... .... ..... .... 74 References. .... .... .... ..... .... .... .... .... .... ..... .... 75