Soft-matter Arti cial Muscle by Electrochemical Surface Oxidation of Liquid Metal Jiahe Liao Master

74 Pages·2017·38.56 MB·English

Soft-matter Arti(cid:1661)cial Muscle
by Electrochemical Surface Oxidation of Liquid Metal
Thesisby
Jiahe Liao
SubmittedtotheRoboticsInstitute
inpartialful(cid:1661)llmentoftherequirementsforthedegreeof
Master of Science in Robotics
at
C M U
ThesisCommittee:
ProfessorCarmelMajidi,Chair
ProfessorMatthewTravers
EricMarkvicka,Ph.D.
August 2018
Soft-matter Arti(cid:1661)cial Muscle
by Electrochemical Surface Oxidation of Liquid Metal
Jiahe Liao
TheRoboticsInstitute
CarnegieMellonUniversity
ProfessorCarmelMajidi,Chair
Abstract
Naturalmuscles,aresultofmorethan500millionsyearsofevolution,areelegantmachines
thatgenerateforceandmotionelectrochemically. Thebriefhistoryofroboticsdoesnothave
theluxuryofmillionsofyearstoreverse-engineermanyaspectsoflife. Thedevelopmentof
arti(cid:1661)cialmusclesthereforeseekstobuildmoremuscle-likeactuatorsforrobots. Recentad-
vancesintheengineeringofsoftmaterialshaveledtotheexplorationofnewparadigmsfor
buildingarti(cid:1661)cialmusclesfrommattersthatsharesimilarpropertieswithbiologicaltissues.
A diversity of physical phenomena has also been used to drive an actuator. Among those
are the control of the surface energy of a liquid metal, which often has a signi(cid:1661)cant sur-
∼ ∼
facetensionwhichbecomespredominantatverysmall( mmand µm)scales. Thiswork
formulates a paradigm for building arti(cid:1661)cial muscles that utilizes eutectic gallium-indium
(EGaIn),aliquidmetalalloy(meltingpoint∼15.5○C)whichhasaverylargesurfacetension
∼
( 624 mN/m) in the absence of surface gallium oxide (Ga O ), as an active material and
2 3
demonstrateskeypointsintherealizationanewclassofarti(cid:1661)cialmusclesbasedonthere-
markable controllability of surface tension by electrocapillarity and surface oxidation with
∼
small voltages ( 1 V). Two different form factors are demonstrated. First, a hybrid struc-
tureofcoilspringandEGaInthatiscapableofcontractioninanaqueoussodiumhydroxide
(NaOH)solutionismodeledandexperimentallycharacterized. Second,acore-shellhybrid
of EGaIn and polyacrylamide-potassium-hydroxide (PAAm-KOH) hydrogel as an equiva-
lent device is hypothesized and validated. Limitations and issues are discussed. A broader
perspectiveisalsoprovidedontheroleanduniquenessofthisarti(cid:1661)cialmuscleparadigmin
thecurrentroboticslandscape.
Acknowledgements
IamdeeplygratefultoProf. CarmelMajidiforhiscontinualguidanceandsupport.
Ithasbeenaprivilegetoworkwithandlearnfrommypreviousandcurrentlabmates. In
particular,IwouldliketoacknowledgeDr. EricMarkvickaforhiskindencouragementand
support,Dr. AlexiCharalambidesforhissharingofexperienceduringmy(cid:1661)rstyear,Hesham
Zainiforourcountlessall-nighters,and(cid:1661)nallyYun-SikOhmforourinspiringcollaboration.
Finally, I wish to thank my family for their love and my friends Yan-Jen Huang and
AshwinKhadkefortheirin(cid:1661)nitesupport.
I
Contents
Acknowledgements I
Contents II
ListofFigures III
ListofTables VII
1 Introduction 2
1.1 MusclesinNature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Arti(cid:1661)cialMusclesforRobots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.1 OverviewofSoftActuators . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.2.2 ActuatorPerformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3 OverviewofSurfaceTensionBasedActuation . . . . . . . . . . . . . . . . . . 18
1.3.1 Electrocapillarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.3.2 SurfaceOxidationofLiquidMetal . . . . . . . . . . . . . . . . . . . . 20
1.4 ThesisObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2 HelicalSpring-LiquidMetalActuator 25
2.1 DesignandFabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2 ExperimentalSetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3 ResultsandDiscussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3.1 Quasi-staticResponse . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3.2 DynamicResponse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.3.3 PerformanceofSpring-LiquidMetalActuators . . . . . . . . . . . . . 34
II
2.4 ConcludingRemarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3 Hydrogel-LiquidMetalHybrids 37
3.1 Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.2 DesignandFabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2.1 GelPreparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2.2 EGaInDeposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3 ResultandDiscussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.4 ConcludingRemarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4 ConclusionandFutureResearch 46
Bibliography 48
III
List of Figures
1.1 Illustrationofnaturalandarti(cid:1661)cialmusclesasstimuli-responsivemachines
thattransformsomeformofenergyintomechanicalwork. Adielectricelas-
tomeractuator(DEA)isusedasanexampleofarti(cid:1661)cialmuscles. . . . . . . . 3
1.2 Imagesofadropletofeutecticgallium-indium(EGaIn)immersedinpotas-
siumhydroxide(KOH)solution. (A)Thedropletisnearlysphericaldueto
highsurfaceenergy. (B)Whengalliumoxideisformedonthesurface, the
∼
droplet(cid:1662)attensduetodrasticallylowered( 0)surfacetension. . . . . . . . . 5
1.3 Imagesofthehierarchyofskeletalmuscle. (a)Caterpillar(b)Muscletissue
(c)AMusclecell(muscle(cid:1661)ber)isabasiccellularunit,whichisabundleof
even smaller (cid:1661)bers called myo(cid:1661)brils. (d) Myo(cid:1661)bril (e) A sarcomere is the
basiccontractileunit. (f)Actin(thin)andmyosin(thick)(cid:1661)lamentsarere-
sponsibleforthemicroscopicslidingandmacroscopiccontractionofmus-
cles. Titin(elastic)(cid:1661)lamentsanchormyosins. Imagesources: (a)from[81],
(b)from[8],(c,d)from[84],(e)from[42],(f)from[114]. . . . . . . . . . . . 6
IV
1.4 Imagesofpreviousworkonarti(cid:1661)cialmuscles,categorizedbymaterials(A1-
A4), energy sources (B1-B4) and actuation principles (C1-C4). (A1) Elas-
tomers(A2)Shape-memoryalloys(A3)Liquidcrystals(A4)Hydrogels(B1)
Electricity (B2) Magnetic Field (B3) Heat (B4) Chemical (C1) Coulomb
forces (C2) Ionic diffusion (C3) Phase transition (C4) Magnetic gradients.
From[109,59,98,137,88,41,90]. . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.5 Plotofstressvs. strainoutputofnaturalmuscles,electricmotor,andelectri-
calarti(cid:1661)cialmuscles. Notethatsomevaluesarecitedfromdifferentsources
andapproximateasinTable1.3. Plotscalesarelogarithmic. . . . . . . . . . . 16
1.6 Plot of work density vs. strain rate of natural muscles, electric motor, and
electrical arti(cid:1661)cial muscles. Note that some values are cited from different
sourcesandapproximateasinTable1.3. Plotscalesarelogarithmic. . . . . . 17
1.7 Plot of operating voltage vs. bandwidth (highest operating frequency) of
natural muscles, electric motor, and electrical arti(cid:1661)cial muscles. Note that
some values are cited from different sources and approximate as in Tables
1.4and1.5. Plotscalesarelogarithmic. . . . . . . . . . . . . . . . . . . . . . . 17
1.8 Illustration of the formation of an electrical double layer on the metal sur-
faceinanelectrolyte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.9 Illustrationofthedissolutionofgalliuminasolutionofsodiumhydroxide
(NaOH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.10 Illustration of gallium oxide skin which effectively acts as a surfactant be-
tweentheEGaInandNaOHduetothehydrophilicityofGa O . . . . . . . . 22
2 3
V
1.11 Comparison of the interfacial tension-potential relationship using electro-
capillarityonlyandusingelectrocapillaritywithsurfaceoxidation. Datare-
producedfrom[60].. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.1 Hill-type model for muscle contraction. The nonlinearlity is abstracted by
three black boxes: a contractile element (CE) and two spring-like elastic
elementsinseries(SE)andinparallel(PE). . . . . . . . . . . . . . . . . . . . . 26
2.2 Illustrationofthedesignofthespring-LMactuator. WorkbyHeshamZaini. 27
2.3 Imageofthefabricationresultandtheexperimentalsetupofthespring-LM
actuator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.4 Images of (A) full contraction and (B) full expansion of a spring-LM ac-
tuator. The full contraction corresponds to -0.5 V and the full expansion
correspondsto1.0VrelativetoNaOHsolution. Theimageanalysisisdone
bytrackingthelowertip(redline)ofthehelix. Scalebarrepresents10mm. 29
2.5 Plotofactuatorlengthvs. potentialoftheelectroderelativetoNaOHsolu-
tionwithatrianglewave(period: 120s). Theactuatorwasloadedwithzero
washers. DatareproducedfromtheimageanalysisbyHeshamZaini. . . . . 30
2.6 Quasi-staticanalysisofaspring-LMactuator. (A)Plotofactuatorlengthvs.
voltageforloadsvaryingfromzerowashers(F = 0)tofourwashers(F =
7:67 mN). (B-D) Work vs. load, length vs. voltage, work vs. voltage taken
overtherangefrom0to1.5V.Datareproducedfromtheimageanalysisby
HeshamZaini. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
VI
2.7 Stepresponseofaspring-LMactuatorshowing(A)step-upfrom-0.5to1V
and(B)step-downfrom1Vto-0.5V.t representsthesettlingtimeforthe
s
actuatortiptoenterwithin5%ofitssteady-stateposition. Datareproduced
fromtheimageanalysisbyHeshamZaini.. . . . . . . . . . . . . . . . . . . . . 33
2.8 Comparison of spring-LM actuators to other actuators in terms of stress
output vs. strain output. Values are approximated (Source are the same as
Figure1.5). Stressoutputisapproximatedusingthecross-sectionalareaof
EGaInbridges,notthespring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.9 Comparison of spring-LM actuators to other actuators in terms of work
density vs. strain rate. Values are approximated (Source are the same as
Figure1.6). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.1 Conceptoftheproposedcaviar-likehydrogel-LMstructure. . . . . . . . . . . 39
3.2 AnEGaIndropletbeingdepositedintoasampleofcuredPAAm-KOHhy-
drogel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3 DemonstrationofEGaInheartbeatsinsidethePAAm-KOHhydrogel. Hy-
drogengasbubblescanbeseenattheelectrodes. . . . . . . . . . . . . . . . . . 43
VII
List of Tables
1.1 Summaryofthehierarchyofmammalskeletalmuscles. Theshortestmuscle
∼
inhumanisthestapedius( 1mm)inthemiddleearandthelargestisthe
∼
sartorius( 600mm)alongthethigh. Theexactlengthofthelongestmuscle
inbluewhales,duetolackofdata,isapproximatedtotheirwholebodylength. 7
1.2 Propertiesofskeletalmuscles. Thelengthscaleoflongestmammalianmus-
cleisapproximatedbythewholebodylengthofbluewhales. . . . . . . . . . 9
1.3 Properties of selected electrical arti(cid:1661)cial muscles. Values marked with †
areapproximate. The(peak) stressrepresentsthemaximumforceperunit
cross-sectionalareathatanarti(cid:1661)cialmuscleisabletogenerate. Thepower-
to-massratioofIPMCsiscalculatedbytakingthemeasurement870W/m3
3
from[7]andthedensity1,500kg/m from[86]. . . . . . . . . . . . . . . . . . 14
VIII