Conventional biomaterials, such as metals, polymers, composites and ceramics, may not work well when facing certain tough medical challenges. As an alternative, body-temperature liquid metals, such as gallium, or its alloys are recently emerging as new generation functional materials which display many unconventional properties superior to traditional biomaterials, i.e. high fluidity, excellent electrical and thermal conductivities, good biocompatibility, sufficient radiopacity, controllable behaviour, easy manufacture and low cost. This article aims to outline a new biomedical category: liquid metal biomaterials. Representative applications enabled by liquid metal biomaterials from both therapeutic and diagnostic aspects were reviewed. Furthermore, related efforts and perspective for future development of employing liquid metals to resolve modern biomedical tough issues were discussed. With continuous technical progresses and fundamental discoveries, liquid metals are expected to offer more and more outstanding merits as a new class of biomaterials which are promising a generalised way towards resolving biomedical challenges.
Get full access to this article
View all access options for this article.
References
1.
MurrayCJBarberRMForemanKJet al.Global, regional, and national disability-adjusted life years (DALYs) for 306 diseases and injuries and healthy life expectancy (HALE) for 188 countries, 1990–2013: quantifying the epidemiological transition. Lancet. 2015;386(10009):2145–2191.
KohnJ.New approaches to biomaterials design. Nat Mater. 2004;3(11):745–747.
4.
HuebschNMooneyDJ.Inspiration and application in the evolution of biomaterials. Nature. 2009;462(7272):426–432.
5.
WilliamsDF.On the nature of biomaterials. Biomaterials. 2009;30(30):5897–5909.
6.
BhatSKumarA.Biomaterials and bioengineering tomorrow’s healthcare. Biomatter. 2013;3(3):e24717-1–e24717-2.
7.
DeanMNSwansonBOSummersAP.Biomaterials: properties, variation and evolution. Integr Comp Biol. 2009;49(1):15–20.
8.
RezaieHRBakhtiariLÖchsnerA.Biomaterials and their applications. Berlin: Springer; 2015.
9.
WebsterTJEjioforJU.Increased osteoblast adhesion on nanophase metals: Ti, Ti6Al4V, and CoCrMo. Biomaterials. 2004;25(19):4731–4739.
10.
BencharitSByrdWCAltarawnehSet al.Development and applications of porous tantalum trabecular metal-enhanced titanium dental implants. Clin Implant Dent R. 2014;16(6):817–826.
11.
HainesCSLimaMDLiNet al.Artificial muscles from fishing line and sewing thread. Science. 2014;343(6173):868–872.
12.
TamuraKMizunoHOkadaKet al.Experimental application of polyvinyl alcohol-silica for small artificial vessels. Biomater Med Devices Artif Organs. 1985;13(3–4):133–152.
13.
AbbottF.The use of fusible alloy in vapor diffusion pumps. Rev Sci Instrum. 1942;13(4):187–187.
14.
BrunettiBGozziDIervolinoMet al.Bismuth activity in lead-free solder Bi–In–Sn alloys. Calphad. 2006;30(4):431–442.
15.
MoelansNKumarKHWollantsP.Thermodynamic optimization of the lead-free solder system Bi–In–Sn–Zn. J Alloys Compd. 2003;360(1):98–106.
16.
CrubzyEMurailPGirardLet al.False teeth of the roman world. Nature. 1998;391(6662):29.
17.
BahraminasabMHassanMRSahariBB.Metallic biomaterials of knee and hip: a review. Trends Biomater Artif Organs. 2013;24(2):69–82.
18.
PoinernGEJBrundavanamSFawcettD.Biomedical magnesium alloys: a review of material properties, surface modifications and potential as a biodegradable orthopaedic implant. Am J Biomed Eng. 2012;2(6):218–240.
19.
StaigerMPPietakAMHuadmaiJet al.Magnesium and its alloys as orthopedic biomaterials: a review. Biomaterials. 2006;27(9):1728–1734.
20.
ValiathanMSKrishnanVK.Biomaterials: an overview. Natl Med J India. 1999;12(6):270–274.
21.
RidzwanMIZShuibSHassanAYet al.Problem of stress shielding and improvement to the hip implant designs: a review. J Med Sci. 2007;7(3):460–467.
22.
ZbergBUggowitzerPJLofflerJF.MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants. Nat Mater. 2009;8:887–891.
23.
LimGB.Interventional cardiology: dreams of a bioabsorbable stent coming true. Nat Rev Cardiol. 2013;10:120.
24.
YinLHuangXXuHet al.Materials, designs, and operational characteristics for fully biodegradable primary batteries. Adv Mater. 2014;26(23):3879–3884.
25.
ZhengYFGuXNWitteF.Biodegradable metals. Mater Sci Eng R. 2014;77(2):1–34.
26.
YunYDongZLeeNet al.Revolutionizing biodegradable metals. Mater Today. 2009;12(10):22–32.
27.
WangLLiuJ.Compatible hybrid 3D printing of metal and nonmetal inks for direct manufacture of end functional devices. Sci China Technol Sci. 2014;57(11):2089–2095.
28.
ZhangQLiuJ.Nano liquid metal as an emerging functional material in energy management, conversion and storage. Nano Energy. 2013;2(5):863–872.
29.
LiuTSenPKimCJ.Characterization of nontoxic liquid-metal alloy galinstan for applications in microdevices. J Microelectromech Syst. 2012;21(2):443–450.
30.
SpellsK.The determination of the viscosity of liquid gallium over an extended nrange of temperature. Proc Phys Soc. 1936;48(2):299–311.
31.
YiLJinCWangLet al.Liquid-solid phase transition alloy as reversible and rapid molding bone cement. Biomaterials. 2014;35(37):9789–9801.
32.
] GauCViskantaR.Melting and solidification of a pure metal on a vertical wall. J Heat Trans-T ASME. 1986;108(1):174–181.
33.
LiHMeiSWangLet al.Splashing phenomena of room temperature liquid metal droplet striking on the pool of the same liquid under ambient air environment. Int J Heat Fluid Flow. 2014;47:1–8.
34.
LiPLiuJ.Harvesting low grade heat to generate electricity with thermosyphon effect of room temperature liquid metal. Appl Phys Lett. 2011;99(9):094106-1–094106-3.
35.
GaoYLiuJ.Gallium-based thermal interface material with high compliance and wettability. Appl Phys A. 2012;107(3):701–708.
36.
LiuJZhouYLvYet al.Liquid metal based miniaturized chip-cooling device driven by electromagnetic pump. ASME 2005 International Mechanical Engineering Congress and Exposition; 2005 Nov 5 – 11; Orlando, Florida, USA. p. 501–510.
37.
WangQLiuJ.Liquid metal based microwave delivery wire, fabrication and application, 2013, China Patents 201310259413.7.
38.
KaltenbrunnerMKettlgruberGSiketCet al.Arrays of ultracompliant electrochemical dry gel cells for stretchable electronics. Adv Mater. 2010;22(18):2065–2067.
FasslerAMajidiC.3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting. Lab Chip. 2013;13(22):4442–4450.
42.
KramerRKMajidiCWoodRJ.Masked deposition of gallium-indium alloys for liquid-embedded elastomer conductors. Adv Funct Mater. 2013;23(42):5292–5296.
43.
YuYWangQYiLet al.Channelless fabrication for large-scale preparation of room temperature liquid metal droplets. Adv Eng Mater. 2014;16(2):255–262.
44.
ScharmannFCherkashininGBreternitzVet al.Viscosity effect on GaInSn studied by XPS. Surf Interface Anal. 2004;36(8):981–985.
45.
ZhangJYaoYShengLet al.Self-fueled biomimetic liquid metal mollusk. Adv Mater. 2015;27(16):2648–2655.
46.
IlyukhinaAIlyukhinAShkolnikovE.Hydrogen generation from water by means of activated aluminum. Int J Hydrogen Energy. 2012;37(21):16382–16387.
47.
WangLLiuJ.Electromagnetic rotation of a liquid metal sphere or pool within a solution. Proc Roy Soc A-Math Phys Eng Sci. 2015;471(2178):20150177.
48.
TanSCGuiHYuanBet al.Magnetic trap effect to restrict motion of self-powered tiny liquid metal motors. Appl Phys Lett. 2015;107(7):071904.
49.
MaKQLiuJ.Nano liquid-metal fluid as ultimate coolant. Phys Lett A. 2007;361(3):252–256.
50.
ChitambarCR.Medical applications and toxicities of gallium compounds. Int J Env Res Public Health. 2010;7(5):2337–2361.
51.
BernsteinLR.Mechanisms of therapeutic activity for gallium. Pharmacol Rev. 1998;50(4):665–682.
52.
RüdelH.Case study: bioavailability of tin and tin compounds. Ecotox Environ Safe. 2003;56(1):180–189.
53.
GrafGG.Tin, tin alloys, and tin compounds. Ullmann's encyclopedia of industrial chemistry. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA;2005.
54.
NakajimaMUsamiMNakazawaKet al.Developmental toxicity of indium: embryotoxicity and teratogenicity in experimental animals. Congenit Anom. 2008;48(4):145–150.
55.
TanakaAHirataMKiyoharaYet al.Review of pulmonary toxicity of indium compounds to animals and humans. Thin Solid Films. 2010;518(11):2934–2936.
56.
CadwalladerLC.Gallium safety in the laboratory. Idaho Falls (ID): Idaho National Engineering & Environment Laboratory;2003.
57.
DunneSAbrahamR.Dental post-operative sensitivity associated with a gallium-based restorative material. Br Dent J. 2000;189(6):310–313.
58.
MohanR.Green bismuth. Nat Chem. 2010;2(4):336.
59.
SanoYSatohHChibaMet al.Oral toxicity of bismuth in rat: single and 28-day repeated administration studies. J Occup Health. 2005;47(4):293–298.
60.
SanoYSatohHChibaMet al.A 13-week toxicity study of bismuth in rats by intratracheal intermittent administration. J Occup Health. 2005;47(3):242–248.
61.
BradleyBSingletonMPoALW.Bismuth toxicity – a reassessment. J Clin Pharm Ther. 1989;14(6):423–441.
62.
SerfonteinWMekelR.Bismuth toxicity in man II. Review of bismuth blood and urine levels in patients after administration of therapeutic bismuth formulations in relation to the problem of bismuth toxicity in man. Res Commun Chem Pathol. 1979;26(2):391–411.
63.
RemennikSBartschIWillboldEet al.New, fast corroding high ductility Mg–Bi–Ca and Mg–Bi–Si alloys, with no clinically observable gas formation in bone implants. Mater Sci Eng. B. 2011;176(20):1653–1659.
64.
ZhangQZhengYLiuJ.Direct writing of electronics based on alloy and metal (DREAM) ink: a newly emerging area and its impact on energy, environment and health sciences. Front Energy. 2012;6(4):311–340.
65.
KimHJSonCZiaieB.A multiaxial stretchable interconnect using liquid-alloy-filled elastomeric microchannels. Appl Phys Lett. 2008;92(1):011904-1–011904-3.
66.
ChengSRydbergAHjortKet al.Liquid metal stretchable unbalanced loop antenna. Appl Phys Lett. 2009;94(14):144103-1–144103-3.
JeongSHHjortKWuZ.Tape transfer printing of a liquid metal alloy for stretchable RF electronics. Sensors. 2014;14(9):16311–16321.
69.
NawazAAMaoXStrattonZSet al.Unconventional microfluidics: expanding the discipline. Lab Chip. 2013;13(8):1457–1463.
70.
JungTYangS.Highly stable liquid metal-based pressure sensor integrated with a microfluidic channel. Sensors. 2015;15(5):11823–11835.
71.
ParkYLMajidiCKramerRet al.Hyperelastic pressure sensing with a liquid-embedded elastomer. J Micromech Microeng. 2010;20(12):125029–125034.
72.
WongRDPPosnerJDSantosVJ.Flexible microfluidic normal force sensor skin for tactile feedback. Sensors Actuat A: Phys. 2012;179:62–69.
73.
ShanWLuTMajidiC.Soft-matter composites with electrically tunable elastic rigidity. Smart Mater Struct. 2013;22(8):085005–085012.
74.
GaoYLiHLiuJ.Direct writing of flexible electronics through room temperature liquid metal ink. PLoS One. 2012;7(9):e45485-1–e45485-11.
75.
LiHYangYLiuJ.Printable tiny thermocouple by liquid metal gallium and its matching metal. Appl Phys Lett. 2012;101(7):073511-1–073511-4.
76.
MeiSGaoYLiHet al.Thermally induced porous structures in printed gallium coating to make transparent conductive film. Appl Phys Lett. 2013;102(4):041905-1–041905-4.
77.
ZhangQGaoYLiuJ.Atomized spraying of liquid metal droplets on desired substrate surfaces as a generalized way for ubiquitous printed electronics. Appl Phys A. 2014;116(3):1091–1097.
78.
BoleyJWWhiteELChiuGTCet al.Direct writing of gallium-indium alloy for stretchable electronics. Adv Funct Mater. 2014;24(23):3501–3507.
79.
ZhengYZhangQLiuJ.Pervasive liquid metal based direct writing electronics with roller-ball pen. AIP Adv. 2013;3(11):6459–6463.
80.
TabatabaiAFasslerAUsiakCet al.Liquid-phase gallium–indium alloy electronics with microcontact printing. Langmuir. 2013;29(20):6194–6200.
WangLLiuJ.Liquid phase 3D printing for quickly manufacturing conductive metal objects with low melting point alloy ink. Sci China Technol Sci. 2014;57(9):1721–1728.
83.
TorreLABrayFSiegelRLet al.Global cancer statistics, 2012. CA – Cancer J Clin. 2015;65(2):87–108.
84.
FoustO.Sodium chemistry and physical properties. New York: Gorden and Breach, Science Publishers, Inc; 1972.
WitschESelaMYardenY.Roles for growth factors in cancer progression. Physiology. 2010;25(2):85–101.
87.
ZetterPBruceR.Angiogenesis and tumor metastasis. Annu Rev Med. 1998;49(1):407–424.
88.
O’ReillyMSBoehmTShingYet al.Endostatin: an endogenous inhibitor of angiogenesis and tumor growth. Cell. 1997;88(2):277–285.
89.
MiaoRQAgataJChaoLet al.Kallistatin is a new inhibitor of angiogenesis and tumor growth. Blood. 2002;100(9):3245–3252.
90.
KeungEZNelsonPJConradC.Concise review: genetically engineered stem cell therapy targeting angiogenesis and tumor stroma in gastrointestinal malignancy. Stem Cells. 2013;31(2):227–235.
91.
QuesadaARMedinaMAAlbaE.Playing only one instrument may be not enough: limitations and future of the antiangiogenic treatment of cancer. Bioessays. 2007;29(11):1159–1168.
92.
WangQYuYLiuJ.Delivery of liquid metal to the target vessels as vascular embolic agent to starve diseased tissues or tumors to death. arXiv preprint arXiv: 1408.0989, 2014.
93.
FelsonDTZhangY.An update on the epidemiology of knee and hip osteoarthritis with a view to prevention. Arthritis Rheum. 1998;41(8):1343–1355.
94.
TaylorDHazenbergJGLeeTC.Living with cracks: damage and repair in human bone. Nat Mater. 2007;6(4):263–268.
95.
BaltzerALiebermanJ.Regional gene therapy to enhance bone repair. Gene Ther. 2004;11(4):344–350.
96.
YangJM.Polymerization of acrylic bone cement using differential scanning calorimetry. Biomaterials. 1997;18(19):1293–1298.
97.
CristofoliniLMinariCVicecontiM.A methodology and criterion for acrylic bone cement fatigue tests. Fatigue Fract Eng Mater Struct. 2000;23(11):953–957.
98.
StańczykMVan RietbergenB.Thermal analysis of bone cement polymerisation at the cement–bone interface. J Biomech. 2004;37(12):1803–1810.
99.
HansenE.Modelling heat transfer in a bone–cement–prosthesis system. J Biomech. 2003;36(6):787–795.
100.
KongKJeonD.Design and control of an exoskeleton for the elderly and patients. IEEE/ASME Trans Mechatron. 2006;11(4):428–432.
101.
PerryJCRosenJBurnsS.Upper-limb powered exoskeleton design. IEEE/ASME Trans Mechatron. 2007;12(4):408–417.
102.
CollinsSHWigginMBSawickiGS.Reducing the energy cost of human walking using an unpowered exoskeleton. Nature. 2015;522(7555):212–215.
103.
BerringJKianfarKLiraCet al.A smart hydraulic joint for future implementation in robotic structures. Robotica. 2010;28(7):1045–1056.
104.
DengYLiuJ.Flexible mechanical joint as human exoskeleton using low-melting-point alloy. J Med Devices. 2014;8(4):044506-1–044506-3.
105.
ParkYLChenBPérez-ArancibiaDNOet al.Design and control of a bio-inspired soft wearable robotic device for ankle–foot rehabilitation. Bioinspir Biomim. 2014;9(1):16007–16023.
106.
LeeSKWolfeSW.Peripheral nerve injury and repair. J Am Acad Orthop Sur. 2000;8(4):243–252.
ScheibJHökeA.Advances in peripheral nerve regeneration. Nat Rev Neurol. 2013;9(12):668–676.
109.
EvansGR.Peripheral nerve injury: a review and approach to tissue engineered constructs. Anat Rec. 2001;263(4):396–404.
110.
GordonTSulaimanOBoydJG.Experimental strategies to promote functional recovery after peripheral nerve injuries. J Peripher Nerv Syst. 2003;8(4):236–250.
111.
ZhangJShengLJinCet al.Liquid metal as connecting or functional recovery channel for the transected sciatic nerve. arXiv preprint arXiv: 1404.5931, 2014.
112.
LiuFYuYYiLet al.Liquid metal as reconnection agent for peripheral nerve injury. Sci Bull. 2016;61(12):939–947.
113.
JinCZhangJLiXet al.Injectable 3-D fabrication of medical electronics at the target biological tissues. Sci Rep. 2013;3:3342.
114.
GomezNSchmidtCE.Nerve growth factor-immobilized polypyrrole: bioactive electrically conducting polymer for enhanced neurite extension. J Biomed Mater Res A. 2007;81A(1):135–149.
115.
KimDHAbidianMMartinDC.Conducting polymers grown in hydrogel scaffolds coated on neural prosthetic devices. J Biomed Mater Res A. 2004;71A(4):577–585.
116.
ZhangZRouabhiaMWangZet al.Electrically conductive biodegradable polymer composite for nerve regeneration: electricity-stimulated neurite outgrowth and axon regeneration. Artif Organs. 2007;31(1):13–22.
117.
LarssonDHLundströmUWestermarkUKet al.First application of liquid-metal-jet sources for small-animal imaging: high-resolution CT and phase-contrast tumor demarcation. Med Phys. 2013;40(2):021909-1–021909-7.
118.
WhartonTWilsonLJ.Highly-iodinated fullerene as a contrast agent for X-ray imaging. Biorg Med Chem. 2002;10(11):3545–3554.
119.
HallouardFBriançonSAntonNet al.Poly(ethylene glycol)-poly(ε-caprolactone) iodinated nanocapsules as contrast agents for x-ray imaging. Pharm Res. 2013;30(8):2023–2035.
120.
LiXAntonNZuberGet al.Iodinated α-tocopherol nano-emulsions as non-toxic contrast agents for preclinical X-ray imaging. Biomaterials. 2013;34(2):481–491.
121.
JensenHDoughtyRWGrantDet al.The effects of the iodinated x-ray contrast media iodixanol, iohexol, iopromide, and ioversol on the rat kidney epithelial cell line NRK 52-E. Renal Fail. 2011;33(4):426–433.
122.
WangQYuYPanKet al.Liquid metal angiography for mega contrast x-ray visualization of vascular network in reconstructing in-vitro organ anatomy. IEEE Trans Biomed Eng. 2014;61(7):2161–2166.
123.
RogersJASomeyaTHuangY.Materials and mechanics for stretchable electronics. Science. 2010;327(5973):1603–1607.
124.
KoHCStoykovichMPSongJet al.A hemispherical electronic eye camera based on compressible silicon optoelectronics. Nature. 2008;454(7205):748–753.
125.
SomeyaTSekitaniTIbaSet al.A large-area, flexible pressure sensor matrix with organic field-effect transistors for artificial skin applications. Proc Natl Acad Sci USA. 2004;101(27):9966–9970.
126.
HammockMLChortosATeeBCKet al.25th anniversary article: the evolution of electronic skin (E-Skin): a brief history, design considerations, and recent progress. Adv Mater. 2013;25(42):5997–6038.
127.
SomeyaTKatoYSekitaniTet al.Conformable, flexible, large-area networks of pressure and thermal sensors with organic transistor active matrixes. Proc Natl Acad Sci USA. 2005;102(35):12321–12325.
128.
SekitaniTTakamiyaMNoguchiYet al.A large-area wireless power-transmission sheet using printed organic transistors and plastic MEMS switches. Nat Mater. 2007;6(6):413–417.
129.
ParkYLChenBrYoungDet al.Bio-inspired active soft orthotic device for ankle foot pathologies. 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS); 2011 Sep 25–30; San Francisco, CA, USA. p. 4488–4495.
130.
KimR-HKimD-HXiaoJet al.Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics. Nat Mater. 2010;9(11):929–937.
131.
KramerRKMajidiCWoodRJ.Wearable tactile keypad with stretchable artificial skin. 2011 IEEE International Conference on Robotics and Automation (ICRA); 2011 May 9–13; Shanghai, China. p. 1103–1107.
132.
MajidiCKramerRWoodR.A non-differential elastomer curvature sensor for softer-than-skin electronics. Smart Mater Struct. 2011;20(10):1487–1490.
133.
ParkYLChenBRWoodRJ.Design and fabrication of soft artificial skin using embedded microchannels and liquid conductors. IEEE Sensors J. 2012;12(8):2711–2718.
134.
MineartKPLinYDesaiSCet al.Ultrastretchable, cyclable and recyclable 1- and 2-dimensional conductors based on physically cross-linked thermoplastic elastomer gels. Soft Matter. 2013;9(32):7695–7700.
135.
YoonJHongSYLimYet al.Design and fabrication of novel stretchable device arrays on a deformable polymer substrate with embedded liquid-metal interconnections. Adv Mater. 2014;26(38):6580–6586.
136.
ShengLTeoSLiuJ.Liquid-metal-painted stretchable capacitor sensors for wearable healthcare electronics. J Med Biol Eng. 2016;36(2):265–272.
ParkJWangSLiMet al.Three-dimensional nanonetworks for giant stretchability in dielectrics and conductors. Nat Commun. 2012;3(2):177–180.
140.
WangQYuYYangJet al.Fast fabrication of flexible functional circuits based on liquid metal dual-trans printing. Adv Mater. 2015;27(44):7109–7116.
141.
ParkMDoKKimJet al.Skin electronics: oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics (Adv. Healthcare Mater. 7/2015). Adv Healthc Mater. 2015;4(7):991–991.
142.
SchwartzGTeeBCMeiJet al.Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring. Nat Commun. 2013;4(5):54–56.
143.
GuoCYuYLiuJ.Rapidly patterning conductive components on skin substrates as physiological testing devices via liquid metal spraying and pre-designed mask. J Mater Chem B. 2014;2(35):5739–5745.
144.
YuYZhangJLiuJ.Biomedical implementation of liquid metal ink as drawable ECG electrode and skin circuit. PLoS One. 2013;8(3):e58771.
145.
QuagliaCBuselliEWebster IIIRJet al.An endoscopic capsule robot: a meso-scale engineering case study. J Micromech Microeng. 2009;19(10):105007-1–105007-11.
146.
CavallottiCPiccigalloMSusiloEet al.An integrated vision system with autofocus for wireless capsular endoscopy. Sensors Actuat A: Phys. 2009;156(1):72–78.
NakazatoYSonobeYToyamaS.Development of an In-pipe micro mobile robot using peristalsis motion. J Mech Sci Technol. 2010;24(1):51–54.
149.
JeonSJangGChoiHet al.Magnetic navigation system for the precise helical and translational motions of a microrobot in human blood vessels. J Appl Phys. 2012;111(7):07E702-1–07E702-3.
150.
ShengLZhangJLiuJ.Diverse transformations of liquid metals between different morphologies. Adv Mater. 2014;26(34):6036–6042.
151.
ZhangJShengLLiuJ.Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects. Sci Rep. 2014;4(11):7116.
152.
ZhangJYaoYLiuJ.Autonomous convergence and divergence of the self-powered soft liquid metal vehicles. Sci Bull. 2015;60(10):943–951.
153.
ShengLHeZYaoYet al.Transient state machine enabled from the colliding and coalescence of a swarm of autonomously running liquid metal motors. Small. 2015;11(39):5253–5261.
154.
ZhangJGuoRLiuJ.Self-propelled liquid metal motors steered by a magnetic or electrical field for drug delivery. J Mater Chem B. 2016;4:5349–5357.
155.
NelsonBJKaliakatsosIKAbbottJJ.Microrobots for minimally invasive medicine. Annu Rev Biomed Eng. 2010;12:55–85.
156.
WernethCMMaungKMBlattnigSRet al.Radiation shielding effectiveness with correlated uncertainties. Radiat Measur. 2014;60:23–34.
157.
DengYLiuJ.Liquid metal based stretchable radiation-shielding film. J Med Devices. 2015;9(1):014502-1–014502-4.
158.
RuppJSchmidtMMünchSet al.Rapid microarray processing using a disposable hybridization chamber with an integrated micropump. Lab Chip. 2012;12(7):1384–1388.
159.
CheePSArsatRAdamTet al.Modular architecture of a non-contact pinch actuation micropump. Sensors. 2012;12(9):12572–12587.
160.
YamahataCLacharmeFBurriYet al.A ball valve micropump in glass fabricated by powder blasting. Sensor Actuat B: Chem. 2005;110(1):1–7.
