• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Recent development of transient electronics

    2016-12-09 08:00:11HuanyuChengVikasVepachedu

    Huanyu Cheng,Vikas Vepachedu

    Department of Engineering Science and Mechanics,Materials Research Institute,The Pennsylvania State University,University Park,PA 16802,USA

    Review

    Recent development of transient electronics

    Huanyu Cheng?,Vikas Vepachedu

    Department of Engineering Science and Mechanics,Materials Research Institute,The Pennsylvania State University,University Park,PA 16802,USA

    H I G H L I G H T S

    ?A number of inorganic materials and their method of application were studied.

    ?Models of reactive diffusion were presented to predict the dissolution behavior.

    ?Various encapsulation approaches were explored as a way to extend the lifetime.

    ?The transient ECG sensor was configured in a stretchable layout.

    A R T I C L EI N F O

    Article history:

    Accepted 26 November 2015

    Available online 15 January 2016

    Transient electronics

    Model of reactive diffusion

    Encapsulation strategy

    Multilayer structures

    Transient electronics are an emerging class of electronics with the unique characteristic to completely dissolve withina programmed periodof time.Sincenoharmful byproducts arereleased,theseelectronics can be used in the human body as a diagnostic tool,for instance,or they can be used as environmentally friendly alternatives to existing electronics which disintegrate when exposed to water.Thus,the most crucial aspect of transient electronics is their ability to disintegrate in a practical manner and a review of the literature on this topic is essential for understanding the current capabilities of transient electronics and areas of future research.In the past,only partial dissolution of transient electronics was possible, however,total dissolution has been achieved with a recent discovery that silicon nanomembrane undergoes hydrolysis.The use of single-and multi-layered structures has also been explored as a way to extend the lifetime of the electronics.Analytical models have been developed to study the dissolution of various functional materials as well as the devices constructed from this set of functional materials and these models prove to be useful in the design of the transient electronics.

    ?2016 The Authors.Published by Elsevier Ltd on behalf of The Chinese Society of Theoretical and Applied Mechanics.This is an open access article under the CC BY license(http://creativecommons.org/ licenses/by/4.0/).

    Contents

    1.Introduction........................................................................................................................................................................................................................21

    2.Hydrolysis of semiconducting materials..........................................................................................................................................................................22

    3.Model of reactive diffusion for transient materials.........................................................................................................................................................23

    4.Dissolution of the device with bi-layered structures......................................................................................................................................................25

    5.Conclusion..........................................................................................................................................................................................................................29

    Acknowledgments.............................................................................................................................................................................................................30

    References...........................................................................................................................................................................................................................30

    1.Introduction

    While the development of modern electronics has typically been concerned with durable devices that function stably over time,the advent of transient electronics takes an opposite approach;the destruction of the said devices is designed to provide unique opportunities.Upon exposure to water,transient electronics disintegrate at a predictable rate while releasing biologically and/or environmentally benign end products[1,2].This ability opensawiderangeofapplicationsfrombio-degradableelectronics to diagnostic/therapeutic implants[3,4].One can use an electronic component,for instance,as a temporary implant in a patient and allow it to safely dissolve on its own without the need for a second surgery[1,5].Ultimately,transient electronics can solve the problemofdisposingelectronicsinasafeandconvenientmanner[6–8].

    The defining quality of transient electronics is their ability to dissolve into non-toxic products upon exposure to water and,naturally,dissolution accounts for a significant amount of research in this field[1,2,9–12].Early research on this topic resulted in achieving the partial dissolution of components through the use of organic materials as substrates[13,14].For instance,organic thinfilmtransistorshavebeendevelopedusingcotton-madepaper[15] as substrate and silk was also shown to be useful as a soluble substrate for implants in the body[16].However,this type of research was limited to the substrate and the electronic devices remained insoluble.

    Fig.1.Proof-of-concept demonstration for transient electronics,with key materials and device structure layout.(a)Image of a device with all components deployed on a thin silk substrate.The device components include transistors,diodes,inductors,capacitors,and resistors,with interconnects and interlayer dielectrics.(b)Schematic illustration in an exploded view,with a top view in the lower right inset.(c)Images showing the time sequence at various dissolution stages in deionized(DI)water.

    More recently however,electronics which are completely soluble have been developed.This relies on a recent,important discovery that semiconductor grade monocrystalline silicon can undergo dissolution in bio-fluids or even water at physiological conditions with a programmed lifetime relevant to applications in biomedicine[1].As the reaction rate of silicon hydrolysis to form silicic acid(Si(OH)4)is exceptionally small,silicon devices were fabricated in extremely thin forms.A nanomembrane of silicon with lateral dimensions similar to conventional circuits but with a thickness of 70 nm has been shown to dissolve in~10 days[1].Via similar chemistry,thin silicon dioxide(SiO2)was selected as a gate dielectric.Taken together with the other dissolvable,inorganic materials such as magnesium(Mg)and magnesium oxide(MgO) for conductors and the interlayer dielectric,respectively,due to their spontaneous reaction with water to form biologically benign Mg(OH)2,silicon nanomembranes provide a basic means for the construction of a transient,electronic device.As a proofof-concept,Fig.1(a)and(b)present a schematic demonstration platform which utilizes silicon nanomembranes(Si NMs)for the semiconductors,magnesium for the conductors,magnesium oxide and silicon dioxide for the dielectrics,and silk for the substrate and packaging materials.The collectively configured devices dissolve and disintegrate when immersed in DI water(Fig.1(c)).

    Surface reactions typically dominate the dissolution behavior for sufficiently large reaction constants.The porosity of the materials(e.g.,Mg,MgO and SiO2)however,was found to be influential as it allows for the diffusion of water through the material,thereby increasing the dissolution rate through an increase in the effective surface area[12].In studying the dissolution of transient electronics,the factors to consider include physical and chemical properties of materials,and certain ambient factors of an aqueous environment.Given the research of these factors and others,analytical models have been developed to solidify the understanding of the dissolution behaviors in transient electronics[1,11,12].Such models can be of great assistance in the design of transient electronics.This review will first provide a comprehensive discussion on the hydrolysis of semiconducting materials with a focus on silicon nanomembranes,followed by the model of reactive diffusion to account for the dissolution behavior of porous materials.When combined with ideas from soft,tissuelike electronic devices,the class of transient electronics provides a viable means to monitor health or deliver care in a minimally obtrusive way.

    2.Hydrolysis of semiconducting materials

    To establish a realistic set of functional materials,knowledge regarding the chemical kinetics of each material is critical, especially that of the hydrolysis of semiconducting materials.At physiological pH levels and temperatures,the dissolution rates of semiconducting materials(e.g.,silicon,silicon–germanium,and germanium)are remarkably small[17].Therefore,in order to minimize the amount of semiconducting materials which must be dissolved,the nanomembrane structure is critical.Dissolution of monocrystalline silicon nanomembranes in phosphate buffered saline(PBS with pH=7.4)at biologically pertinent temperatures (e.g.,37°C)forms either an intermediate oxidation product SiO2or Si(OH)4through the equilibrium:Si+4H2O?Si(OH)4+2H2[18,19].Theratedependsonthecrystalstructure,morphology,and doping concentration of silicon[20,21],as well as the temperature and composition of solutions[2,19].

    Systematic characterization of the dissolution kinetics for siliconusedvariousbio-fluidsatmultiplepHlevelsandtemperatures. Patterned Si NMs(3μm×3μm×70 nm)were first created on a layer of thermal oxide on a silicon wafer,followed by immersion in aqueous buffer solutions(50 mL,in a petri dish with diameter of 7 cm).The dissolution rate of thermal oxide is negligible in comparison to that of silicon.Thicknesses of Si NMs were measured at a specific time(e.g.,every other day)after which the sample wasplaced into a fresh buffer solution.There was no significant change in the dissolution rate for a variety of time intervals(e.g.,for every 1,2,4,7 days),indicating accurate measurement in the dissolution rate.Studies of SiGe and Ge were given in a similar setup[17].Figure 2(a)presents atomic force microscope topographical images of a Si NM with an initial thickness of 70 nm collected at various stages of hydrolysis,demonstrating its transient behavior in biofluids(PBS with pH of 7.4;37°C).

    Fig.2.Experiments of silicon dissolution with corresponding theoretical and numerical analyses.(a)Atomic force microscope topographical images of a Si NM with initial dimension of 3μm×3μm×70 nm at various stages of hydrolysis in PBS at 37°C.(b)Theoretical(lines)and experimental(symbols)dissolution of Si NMs from(a)in buffer solutions at different pH levels(pH 6,black;pH 7,red;pH 8,blue;pH 10,purple),at physiological temperature(37°C).(c)Atomic configurations for each ion adsorption event in density functional theory(DFT)simulation of the silicon dissolution process.(For interpretation of the references to color in this figure legend,the reader is referred to the web version of this article.)

    Given the dense arrangement of the silicon atoms in crystal structures,the hydrolysis of monocrystalline silicon nanomembranesislimitedtothesurfaceandthekineticscanbedescribedby a surface reaction with a constant dissolution rate[1,2].With the assumption that no solution molecules diffuse into the silicon,this modelyieldsalinearrelationshipbetweenthemeasuredthickness and the time,where the slopes represent the dissolution rates.A previously established empirical formula[19]suggests that an increase in the hydroxide ion concentration[OH?]results in an accelerated dissolution rate in high pH solutions of KOH.As shown in Fig.2(b),this formula can reproduce the experimental trends for solutions at the physiological pH levels if a different power law exponent is used for[OH?][2].

    3.Model of reactive diffusion for transient materials

    In addition to surface reactions,the diffusion in the porous materials cannot be ignored and the reaction between the diffused molecules and surrounding porous materials also needs to be considered.A model of reactive diffusion was proposed to analytically study the dissolution process of porous materials[23].Themodelconsidersthediffusionofwaterandhydroxideionsinto porous materials,which effectively increases the reactive surface. Here the key parameters are the diffusivity D of water in the porousmaterialandthereactionconstantkbetweenwaterandthe material.Becausetheinitialthicknessh0ismuchsmallerthanboth the width and length of the sample in the experiment,the onedimensional(1D)model can adequately capture the dissolution behaviors.Withy=0atthebottomofthemateriallayer(Fig.4(a)), the water concentrationw(y,t)at location y and time t satisfies the reactive diffusion equation[23]

    This equation reduces to the standard diffusion equation if the reaction constant k is negligible.The boundary conditions of Eq.(1) include a constant water concentration at the water/porous material interfaceand a zero water flux at the porous material/substrate interface?w/?y|y=0=0.The initial condition is zero water concentrationIn order to transform the inhomogeneous boundary conditionto a homogeneous one,a new variableis introduced[12],which results in an updated equation

    The boundary conditions and the initial condition becomeandrespectively.Eq.(2)is inhomogeneous,but the general solution can be represented by a sum of a homogeneous solutionθhand a particular solutionθp.The homogeneous solutionθhsatisfies the homogeneous equationwith homogeneous boundary conditionsand. Expressed in the form ofcan be solved by the method of separation of variables.The homogeneous equation leads towhereλis the eigenvalue to be determined from the boundary condition.The functions T(t)and Y(y)are then expressed as T=e?λtandwhere A and B are constants to be determined from initial and boundary conditions.Withandobtained from the homogeneous boundary conditions,A is solved to be A=0 and the trigonometric equationleads to the solution for eigenvaluesk(n=1,2,3,...),whichin turngivesthehomogeneous solution

    The solution given above indicates a clear scaling lawin which the normalized water concentrationw/w0depends on normalized position y/h0,normalized timeand a single non-dimensional parameterthat scales with the ratio of reaction constant k to diffusivity D.Experimental measurement of Mg with an initial thickness of 300 nm showsandwhich is within the range of reaction constants reported by Taub et al.[24].Figure 3(a)presents the distribution of water concentration for the normalized time0.2,0.4,0.8, 2 and∞,wherecorresponds to the steady-state limit of the water concentration in the Mg layerw(y,t→∞)=

    whereρis the mass density of the porous material.For parameters k and D relevant to applications of transient electronics in biomedicine,the summation on the right hand side of Eq.(5)is negligible in linear expression for the thickness as

    is the critical time of complete physical disappearance for the transient material.The rate of dissolutionalso known as the electrical dissolution rate used for conductors[25],can be determined from the linear approximation of the thickness asThe rate of dissolution is 0.044 nm/s, 0.13 nm/s,and 0.20 nm/s for 100 nm-,300 nm-and 500 nmthick Mglayers,respectively.Thesequantitieshavethe same order of magnitude as rates of dissolution reported in the prior experiments[26,27].

    The chemical reaction of Mg in phosphate buffered saline follows Mg+2H2O→Mg(OH)2+H2.Thus,two water molecules react with one Mg atom(i.e.,q=2).Because water molecules are the dominant molecule in phosphate buffered saline or the other bio-fluids,the water concentration is approximatelyw0= 1 g·cm?3.The critical time tcto dissolve Mg(molar mass M= 24 g·mol?1,mass densityρ=1.738 g·cm?3,and initial thickness h0=300 nm)is calculated as 38 min,which agrees reasonably well with the measurement of 40 min in the experiment.Via a similar chemistry,one silicon oxide atom reacts with two water molecules by SiO2+2H2O→Si(OH)4.Because the reactionbetween SiO2and water is much slower than between Mg and water(minutes to dissolve Mg versus days to dissolve SiO2),the reaction constant between water and SiO2(~10?6s?1)is much smaller than that between water and Mg(~10?3s?1).The rates of dissolution range from 0.11 to 0.47 nm/h for SiO2with an initialthicknessbetween35and100nmatatemperaturebetween room and physiological temperatures.These rates of dissolution for PECVD SiO2in water are consistent with the rates reported in priorexperiments[28],whicharehigherthanthoseforquartz[29].

    In comparison to the intermittent thickness measurement, electrical properties can potentially provide continuous measurements.Electrical measurements also allow for evaluation of the dissolution behavior of a conductive material below a nonconductive layer,as discussed in the next section.The relative changes in both the width and length directions are much smaller than in the thickness direction.Therefore,the electric resistance is inversely proportional to the remaining thickness as R=R0h0/h≈R0/(1?t/tc),where R0is the initial resistance.Changes of resistance approximately account for both changes in thickness and influences associated with porosity,pitting and other nonuniformitiesinducedbynon-uniformdissolution[25].ThenormalizedelectricresistanceR/R0ofMgisshowninFig.4(c)asafunction of the normalized time t/tc.In this figure,the same reaction constant k=1.2×10?3s?1and diffusivity D=6.0×10?12cm2/s arechosenforMgwithan initialthicknessof300nmandinitial resistance(per unit length)R0of 1.06Ω/mm.It is important to note that an initial layer of thin MgO may exist on top of the Mg layer. In the presence of water,this thin MgO layer quickly reacts to form a more stable,crystalline hydroxide[30],which is not as protective as non-crystalline films[31].Thus,the single-layer dissolution model can properly account for the hydrolysis of Mg.

    The potential of thin films made from other transient metals for use in transient electronics has also been explored and was found to be worth considering with the development of MOSFETs as an example[25].Analytical models discussed above are found to be applicable to other dissolvable metals,including Mg alloy, zinc(Zn),tungsten(W),and molybdenum(Mo).The prediction from the model can reproduce the observed dissolution behaviors inDIwaterandsimulatedbodyfluids(e.g.,Hanks’solutionwithpH from5to8)[25].Particularly,theelectricaldissolutionratesinthin films can be much different from traditionally reported corrosion rates in corresponding bulk materials.The model cannot,however, capture the dissolution behavior of iron(Fe),because Fe degrades in a spatially non-uniform manner,with certain reaction products (Fe2O3and Fe3O4)that have very low solubility[25].

    Silicon oxides and silicon nitrides are key materials for dielectrics and encapsulation layers in the class of silicon-based high performance electronics.The dissolution rates of these materials are affected by the physical and chemical properties of the films,which in turn depend on the deposition/growth methods and conditions.A key parameter that can approximately characterize these differences is density.The effects of density variation are two-fold.Reduced density increases the porosity in the porous materials,which results in an increased reactive surface to accelerate the dissolution.Secondly,it also reduces the amountofmaterialsthatneedtobedissolved.Theeffectivedensity ρeffof porous material is related to the densityρsof the fully dense materials asρeff= ρsVs/(Vs+Vair),where Vsand Vairare the volumes of the porous material and air cavity,respectively. A modified version of the reactive diffusion model provides a simple means to account for the density variation[11].In Eq.(1),the diffusivity D is replaced with an effective diffusivity De. The effective diffusivity of water in a porous medium is linearly proportional to the pore fraction in the porous medium:De∝Vair/(Vair+Vs)=(ρs?ρeff)/ρs.As densities of porous materials fromvariousdepositionmethods/conditionsaremeasureddirectly from the experiment,the effective diffusivity of water in each porous material can be determined.At time t=0,the air pores are filled with water,i.e.,w|t=0=w0(ρs?ρeff)/ρs(0≤y<h0). The boundary conditions remain the same as those for Eq.(1). Following the same approach discussed above,the normalized thickness is solved as[11]

    4.Dissolution of the device with bi-layered structures

    Applications in biomedicine require the transient electronics to function stably in a certain timeframe,followed by a complete physical disappearance.All of the transient materials however, start to dissolve immediately in the bio-fluids.The lifetime of the resulting devices is typically determined by Mg interconnects due totheirfastreactionwithwater.Althoughthesystemmayfunction before it completely breaks down,its performance is significantly compromised.Therefore,it is important to explore a mechanism that allows devices to function in a programmed lifetime.

    Adding encapsulation layers or packaging materials on top of the device can extend its lifetime in a controlled manner. For instance,MgO can serve as an encapsulation layer for Mg. In this bi-layered system(Fig.4(b)),zero initial condition at t=0 applies to both Mg and MgO layers.The reactive diffusion Eq.(1)together with zero water flux boundary condition at the bottom surface y=0 still holds for the Mg layer.As for the MgO encapsulation with an initial thickness ofthe reactive diffusion equation becomes[12]whereandare the diffusivity of water in MgO and reaction constant between MgO and water,respectively.The constant water concentration boundary condition at the MgO/water interface isIn addition,the continuity conditions of water concentration and flux across the MgO/Mg interface areandSimilar to the single-layer system,theinhomogeneous boundary condition leads to a representation of the water concentration as a sum of a homogeneous solutionwhand a particular solutionwp,i.e.,w=wh+wp.The homogeneous solutionwhsatisfies the homogeneous equationwhereandfor 0≤ y≤ h0in the Mg layer,andandfor h0≤in the MgO encapsulation.The boundary conditions become homogeneous as well,i.e.,

    and fn(y)is written as

    Satisfying the reactive diffusion equation,together with inhomogeneousboundarycondition,zerowaterfluxatthebottom of Mg layer,and continuity conditions,the particular solutionwpis solved aswp=w0g(y),where

    In the same manner as described in the previous section,the remaining thickness h of the Mg layer normalized by its initial thickness h0is obtained as

    whereGisgiveninEq.(10a).AsMgisbelowtheMgOencapsulation layer,itisdifficulttomeasurethethicknesschangeofMg.Noticing MgO is not conductive,the electric resistance of Mg(or this bilayered structure)is then measured,from which the thickness can be calculated h=R0h0/R.To understand the thickness effect of MgO encapsulation,both 400 nm-thick and 800 nm-thick MgO layers are studied on a 300 nm-thick Mg layer.As shown in Fig.4(c),the normalized electrical resistance R/R0versus the normalized timepredicted from the theory agrees well with the experimental measurements.A comparison between two Mg+MgO structure layouts indicates a substantial increase in the dissolution time as the thickness of encapsulation layer increases. ThiscomesfromthefactthatthediffusionofwaterinMgOismuch slowerthanthatinMg,whicheffectivelyextendsthelifetimeofMg in providing an effective way to control the dissolution time.

    The summation on the right hand side of Eq.(12)is negligible for devices relevant totransient implants.As a result,the thickness decreases linearly with time.The simple and approximate expression is given aswhere is the critical time for complete physical disappearance of the Mg conductor layer in the device and tcis the critical time in the single-layer system.From the remaining thickness h,the rate of dissolution can be solved as′.The rateofdissolutionisapproximatelylinearwiththeinitialthickness h0and it can be further simplified for a sufficiently thin Mg layer

    Fig.3.Distribution of water concentration predicted from models of reactive diffusion for the normalized timeand∞in(a)an Mg layerwithoutencapsulationlayer,and(b)bothanMgconductorlayerencapsulatedbyanMgOlayer

    Fig.4.Schematic illustrations for models of reactive diffusion and modeling predictions of the electrical resistance compared with experimental measurements.(a)Singlelayered structure and(b)bi-layered structure used in models of reactive diffusion for porous materials.(c)Experimental and modeling results of the electric resistance of Mg and Mg with different encapsulation strategies(e.g.,MgO encapsulation layers and/or silk overcoats).

    Fig.5.Encapsulation strategies with multilayer structures.(a)Schematic illustrations of encapsulation methods for transient electronic devices,with defects(e.g.,pinholes) covered by a bilayer of SiO2/Si3N4(left)or an ALD layer(right).(b)Measurements of changes in resistance of Mg traces with an initial thickness of 300 nm encapsulated with different encapsulation approaches(in deionized water at room temperature).Encapsulation strategies examined here include a single layer of PECVD SiO2(black, 1μm),PECVD-LF Si3N4(red,1μm)and ALD SiO2(orange,20 nm);a double layer of PECVD SiO2/PECVD-LF Si3N4(blue,500/500 nm),PECVD SiO2/ALD SiO2(magenta, 500/20 nm),PECVD-LF Si3N4/ALD SiO2(purple,500/20 nm);and a triple layer of PECVD SiO2/PECVD-LF Si3N4(Cyan,200/200/200/200/100/100 nm).(c)Fabrication strategy for the multilayer silk pocket.Crystallization of the outer layers renders them water insoluble,whereas the inner device substrate layer can remain crystallized.Sealing the outer edges around the device encapsulates it in a protective silk pocket.Multilayer fabrication is carried out by repeating the process with an inner pocket as the device layer.(For interpretation of the references to color in this figure legend,the reader is referred to the web version of this article.)

    As an alternative,silicon oxides and nitrides can also be considered as encapsulation layers in addition to their use as gate and interlayer dielectrics,as they are typically known to be barrier materials for permeation of water[11].As a primary source of leakage for vapors or fluids,defects such as pinholes are commonly found in films of silicon oxides and nitrides.As a result,multilayer structures with different materials[11]have been developed to cooperatively eliminate defects[32]for use in transient electronics.In addition to a combination of multiple different layers,i.e.SiO2and Si3N4(Fig.5(a)left),atomic layer deposition(ALD)provides a complementary strategy to reduce defects and improve the performance of the encapsulation,even with thin layers(Fig.5(a),right)[33].As shown in Fig.5(b), measured changes in resistance of a serpentine-shaped Mg trace with an initial thickness of 300 nm demonstrate the effectiveness of several encapsulation approaches.

    To achieve an even longer desired lifetime for transient electronic devices,silk overcoats have also been used to provide an extra barrier for water to diffuse into MgO and Mg layers[1]. A well designed layout with both MgO encapsulation and silk overcoat can successfully increase the lifetime of devices over hundreds of times[12].To apply the idea of multilayer structures to silk overcoats,an encapsulation strategy of exploiting multiple air pockets has been demonstrated[34].A scheme of this strategy is shown in Fig.5(c).Transient electronics transferred to a silk substrate are enclosed by silk films with tunable crystalline and diffusion properties.Thermal sealing of the silk films creates a small air pocket,which provides additional protection for the device components.Iteration of this process can provide multiple silk pockets as needed.The onset of device degradation starts only when swelling of the silk protective layer collapses the air pocket in a wet environment[35].

    Fig.6.Transient electrophysiological sensors configured in a stretchable pattern for capacitive sensing.(a)Optical image of a device and(inset)magnified view of electrode structures in the filamentary serpentine mesh layout.(b)Schematic illustration in an exploded view for the corresponding device in(a).(c)Photograph of a device mounted onthe chestformeasurement ofelectrocardiograms(ECG).(d)ECGmeasurements collectedfrom transient(red)andstandardgel-based(blue)devices.(e)Aseries ofimages at various dissolution stages of a transient device in PBS(pH 10)at room temperature.(For interpretation of the references to color in this figure legend,the reader is referred to the web version of this article.)

    These combined strategies in encapsulation lead to two-stage dissolution kinetics in transient electronics:(i)encapsulation layers define the first time period of stable operation with negligiblechangesinelectricalperformance,(ii)theMgdefinesthe second,where the device rapidly degrades.Efficient encapsulation strategies can remove the leakage pathways and significantly increase the time for stable operation.Realizing the full potential of transient electronics for implanted applications ultimately requires conformal contact with organs of the body.To this end, a recent development of transient medical devices exploits the conceptsofstretchableelectronics[36–40]byuseofbiodegradable elastomers[41].As shown in optical images and schematic illustrations(Fig.6(a)and(b)),a stretchable and transient electrophysiology sensor is constructed.Thin layers of Mg (300nm)andSiO2(100nm)aredesignedintheformoffilamentary serpentine meshes[42–44](Fig.6(a),inset)for measurement, ground and reference electrodes and connecting leads.Capacitive sensing leads to the use of a biodegradable polymer[45,46] between the Mg electrodes and the skin.The measurements show levelsoffidelitycomparabletothoseofconventionalgelelectrodes (Fig.6(d)),as demonstrated in the high quality ECG measurements on the chest(Fig.6(c)).Figure 6(e)presents a set of images of a transient electrophysiology sensor at various dissolution stages in PBS(pH 10)at room temperature.The dissolution behavior of each component is consistent with separate studies of these materials discussed in the previous section(complete dissolution within hours for Mg or days/weeks for SiO2).

    5.Conclusion

    When exposed to bio-fluids or water,the class of siliconbased high performance transient electronics disintegrates and dissolves to eliminate the need for recollection.A number of discoveries have been made in the effort to control how transient electronics dissolve.Firstly,a number of materials,including semiconductors,and their method of application in the design of transient electronics were studied.Secondly,a model of reactive diffusion was presented to predict the way in which a component would dissolve in bio-fluids or water.This model considered a variety of factors including the porosity of the material.Thirdly, this model was extended to study the reactive diffusion in a bilayered structure.The analytical results connect the key electricalproperty to models of reactive diffusion and provide the capability to use such analytics in conjunction with established circuit simulators as a comprehensive design approach.

    Since the nature of the materials used in transient electronics exhibits a decisive effect on the dissolution of resulting electronics,future material science research would be desirable. Other strategies besides encapsulation would also be worth future research to understand multiple ways of controlling the dissolution behavior of transient electronics.Active control of the transience in devices is of interest for the future development as well. Combining possibilities in transient electronics with ideas in soft,‘tissue-like’devices further expands opportunities for applications in biomedicine.Overall,however,the research performed thus far on the design of transient electronics has been extensive and the potential use of this technology in industry is evident.

    Acknowledgments

    H.C.was a Howard Hughes Medical Institute International Student Research fellow.The authors acknowledge the start-up fund provided by the Engineering Science and Mechanics Department, College of Engineering,and Materials Research Institute at the Pennsylvania State University(215-37 1001 cc:H.Cheng).

    References

    [1]S.-W.Hwang,H.Tao,D.-H.Kim,et al.,A physically transient form of silicon electronics,Science 337(2012)1640–1644. http://www.sciencemag.org/content/337/6102/1640.

    [2]S.W.Hwang,G.Park,H.Cheng,et al.,25th anniversary article:Materials for high-performance biodegradable semiconductor devices,Adv.Mater.26 (2014)1992–2000. http://onlinelibrary.wiley.com/doi/10.1002/adma.201470082/abstract.

    [3]R.O.Darouiche,Treatment of infections associated with surgical implants,N. Engl.J.Med.350(2004)1422–1429. http://www.nejm.org/doi/full/10.1056/NEJMra035415.

    [4]H.Tao,S.-W.Hwang,B.Marelli,et al.,Silk-based resorbable electronic devices for remotely controlled therapy and in vivo infection abatement,Proc.Natl. Acad.Sci.111(2014)17385–17389. http://www.pnas.org/content/111/49/17385.abstract.

    [5]C.Dagdeviren,S.W.Hwang,Y.Su,et al.,Transient,biocompatible electronics and energy harvesters based on ZnO,Small 9(2013)3398–3404. http://onlinelibrary.wiley.com/doi/10.1002/smll.201300146/abstract.

    [6]H.L.Hernandez,S.K.Kang,O.P.Lee,et al.,Triggered transience of metastable poly(phthalaldehyde)for transient electronics,Adv.Mater.26(2014) 7637–7642. http://onlinelibrary.wiley.com/doi/10.1002/adma.201403045/abstract.

    [7]C.H.Lee,S.K.Kang,G.A.Salvatore,et al.,Wireless microfluidic systems for programmed,functional transformation of transient electronic devices,Adv. Funct.Mater.25(2015)5100–5106. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201502192/abstract.

    [8]C.W.Park,S.K.Kang,H.L.Hernandez,et al.,Thermally triggered degradation of transient electronic devices,Adv.Mater.27(2015)3783–3788. http://onlinelibrary.wiley.com/doi/10.1002/adma.201501180/abstract.

    [9]X.Huang,Y.Liu,S.W.Hwang,et al.,Biodegradable materials for multilayer transient printed circuit boards,Adv.Mater.26(2014)7371–7377. http://onlinelibrary.wiley.com/doi/10.1002/adma.201403164/abstract.

    [10]S.W.Hwang,S.K.Kang,X.Huang,et al.,Materials for programmed,functional transformation in transient electronic systems,Adv.Mater.27(2015)47–52. http://onlinelibrary.wiley.com/doi/10.1002/adma.201403051/abstract.

    [11]S.K.Kang,S.W.Hwang,H.Cheng,et al.,Dissolution behaviors and applications of silicon oxides and nitrides in transient electronics,Adv.Funct.Mater.24 (2014)4427–4434. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201304293/abstract.

    [12]R.Li,H.Cheng,Y.Su,et al.,An analytical model of reactive diffusion for transient electronics,Adv.Funct.Mater.23(2013)3106–3114. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201203088/abstract.

    [13]C.J.Bettinger,Z.Bao,Organic thin-film transistors fabricated on resorbable biomaterial substrates,Adv.Mater.22(2010)651–655. http://onlinelibrary.wiley.com/doi/10.1002/adma.200902322/abstract.

    [14]M.Irimia-Vladu,P.A.Troshin,M.Reisinger,et al.,Biocompatible and biodegradable materials for organic field-effect transistors,Adv.Funct.Mater. 20(2010)4069–4076. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201001031/abstract.

    [15]F.Eder,H.Klauk,M.Halik,et al.,Organic electronics on paper,Appl.Phys.Lett. 84(2004)2673–2675. http://scitation.aip.org/content/aip/journal/apl/84/14/10.1063/1.1690870.

    [16]D.H.Kim,Y.S.Kim,J.Amsden,et al.,Silicon electronics on silk as a path to bioresorbable,implantable devices(vol 95,133701,2009),Appl.Phys.Lett.95 (2009). http://scitation.aip.org/content/aip/journal/apl/95/13/10.1063/1.3238552.

    [17]S.-K.Kang,G.Park,K.Kim,et al.,Dissolutionchemistryandbiocompatibilityof silicon-and Germanium-based semiconductors for transient electronics,ACS Appl.Mater.Interfaces 7(2015)9297–9305. http://pubs.acs.org/doi/abs/10.1021/acsami.5b02526.

    [18]J.D.Rimstidt,H.L.Barnes,The kinetics of silica–water reactions,Geochim. Cosmochim.Acta 44(1980)1683–1699. http://www.sciencedirect.com/science/article/pii/0016703780902203.

    [19]H.Seidel,L.Csepregi,A.Heuberger,et al.,Anisotropic etching of crystalline silicon in Alkaline-solutions.1.Orientation dependence and behavior of passivation layers,J.Electrochem.Soc.137(1990)3612–3626. http://jes.ecsdl.org/content/137/11/3612.

    [20]S.-W.Hwang,G.Park,C.Edwards,et al.,Dissolution chemistry and biocompatibility of single-crystalline silicon nanomembranes and associated materials for transient electronics,ACS Nano 8(2014)5843–5851. http://pubs.acs.org/doi/abs/10.1021/nn500847g.

    [21]H.Seidel,L.Csepregi,A.Heuberger,et al.,Anisotropic etching of crystalline silicon in Alkaline-solutions.2.Influence of dopants,J.Electrochem.Soc.137 (1990)3626–3632.http://jes.ecsdl.org/content/137/11/3612.

    [22]L.Yin,A.B.Farimani,K.Min,et al.,Mechanisms for hydrolysis of silicon nanomembranes as used in bioresorbable electronics,Adv.Mater.27(2015) 1857–1864. http://onlinelibrary.wiley.com/doi/10.1002/adma.201404579/abstract.

    [23]P.V.Danckwerts,Absorption by simultaneous diffusion and chemical reaction,Trans.Faraday Soc.46(1950)300.http://pubs.rsc.org/en/Content/ ArticleLanding/1950/TF/TF9504600300#!divAbstract.

    [24]I.A.Taub,W.Roberts,S.LaGambina,etal.,Mechanismofdihydrogenformation in the magnesium–water reaction?J.Phys.Chem.A 106(2002)8070–8078. http://pubs.acs.org/doi/abs/10.1021/jp0143847.

    [25]L.Yin,H.Cheng,S.Mao,et al.,Dissolvablemetalsfor transientelectronics,Adv. Funct.Mater.24(2014)645–658. http://onlinelibrary.wiley.com/doi/10.1002/adfm.201301847/abstract.

    [26]H.Inoue,K.Sugahara,A.Yamamoto,et al.,Corrosion rate of magnesium and its alloys in buffered chloride solutions,Corros.Sci.44(2002)603–610. http://www.sciencedirect.com/science/article/pii/S0010938X01000920.

    [27]W.Ng,K.Chiu,F.Cheng,Effect of pH on the i in vitro/i corrosion rate of magnesium degradable implant material,Mater.Sci.Eng.C 30(2010)898–903. http://www.sciencedirect.com/science/article/pii/S0928493110000895.

    [28]G.Wirth,J.Gieskes,The initial kinetics of the dissolution of vitreous silica in aqueous media,J.Colloid Interface Sci.68(1979)492–500. http://www.sciencedirect.com/science/article/pii/0021979779903072.

    [29]W.G.Worley,DissolutionKineticsandMechanismsinQuartz-and Grainite-WaterSystems,MassachusettsInstituteofTechnology,1994, http://dspace.mit.edu/handle/1721.1/28068.

    [30]M.Pourbaix,Atlas of Electrochemical Equilibria in Aqueous Solutions,1974.

    [31]J.P.Hoare,Oxide film studies on iron in electrochemical machining electrolytes,J.Electrochem.Soc.117(1970)142–145. http://jes.ecsdl.org/content/117/1/142.abstract.

    [32]J.Rosink,H.Lifka,G.Rietjens,et al.,34.1:Ultra-thin encapsulation for largearea OLED displays.Paper Presented at:SID Symposium Digest of Technical Papers,Wiley Online Library,2005. http://onlinelibrary.wiley.com/doi/10.1889/1.2036236/abstract.

    [33]J.Meyer,P.G?rrn,F.Bertram,et al.,Al2O3/ZrO2 nanolaminates as ultrahigh gas-diffusion barriers—A strategy for reliable encapsulation of organic electronics,Adv.Mater.21(2009)1845–1849. http://onlinelibrary.wiley.com/doi/10.1002/adma.200803440/abstract.

    [34]M.A.Brenckle,H.Cheng,S.Hwang,et al.,Modulated degradation of transient electronic devices through multilayer silk fibroin pockets,ACS Appl.Mater. Interfaces(2015). http://pubs.acs.org/doi/abs/10.1021/acsami.5b06059?journalCode=aamick.

    [35]B.D.Lawrence,S.Wharram,J.A.Kluge,et al.,Effect of hydration on silk film material properties,Macromol.Biosci.10(2010)393–403. http://www.ncbi.nlm.nih.gov/pubmed/20112237.

    [36]H.Cheng,Y.Zhang,K.-C.Hwang,et al.,Buckling of a stiff thin film on a prestrained bi-layer substrate,Int.J.Solids Struct.51(2014)3113–3118. http://www.sciencedirect.com/science/article/pii/S002076831400198X.

    [37]H.Cheng,J.Wu,M.Li,et al.,An analytical model of strain isolation for stretchable and flexible electronics,Appl.Phys.Lett.98(2011)061902. http://scitation.aip.org/content/aip/journal/apl/98/6/10.1063/1.3553020.

    [38]D.-H.Kim,N.Lu,R.Ma,et al.,Epidermal electronics,Science 333(2011) 838–843.https://www.sciencemag.org/content/333/6044/838.abstract.

    [39]J.A.Rogers,T.Someya,Y.G.Huang,Materials and mechanics for stretchable electronics,Science 327(2010)1603–1607. http://www.sciencemag.org/content/327/5973/1603.abstract.

    [40]J.Viventi,D.H.Kim,J.D.Moss,et al.,A conformal,bio-interfaced class of silicon electronics for mapping cardiac electrophysiology,Sci.Transl.Med.2(2010) http://pubs.acs.org/doi/abs/10.1021/jp0143847.

    [41]S.-W.Hwang,C.H.Lee,H.Cheng,et al.,Biodegradable elastomers and silicon nanomembranes/nanoribbons for stretchable,transient electronics, and biosensors,Nano Lett.15(2015)2801–2808. http://pubs.acs.org/doi/abs/10.1021/nl503997m.

    [42]D.H.Kim,J.L.Xiao,J.Z.Song,et al.,Stretchable,curvilinear electronics based on inorganic materials,Adv.Mater.22(2010)2108–2124. http://onlinelibrary.wiley.com/doi/10.1002/adma.200902927/abstract.

    [43]D.H.Kim,J.H.Ahn,W.M.Choi,et al.,Stretchable and foldable silicon integrated circuits,Science 320(2008)507–511. http://www.sciencemag.org/content/320/5875/507.

    [44]R.H.Kim,M.H.Bae,D.G.Kim,et al.,Stretchable,transparent graphene interconnects for arrays of microscale inorganic light emitting diodes on rubber substrates,Nano Lett.11(2011)3381–3886. http://pubs.acs.org/doi/abs/10.1021/nl202000u.

    [45]S.W.Hwang,J.K.Song,X.Huang,et al.,High-performance biodegradable/transient electronics on biodegradable polymers,Adv.Mater.26(2014) 3905–3911. http://onlinelibrary.wiley.com/doi/10.1002/adma.201306050/abstract.

    [46]J.Yang,A.R.Webb,G.A.Ameer,Novel citric acid–based biodegradable elastomers for tissue engineering,Adv.Mater.16(2004)511–516. http://onlinelibrary.wiley.com/doi/10.1002/adma.200306264/abstract.

    10 October 2015

    http://dx.doi.org/10.1016/j.taml.2015.11.012

    2095-0349/?2016 The Authors.Published by Elsevier Ltd on behalf of The Chinese Society of Theoretical and Applied Mechanics.This is an open access article under the CC BY license(http://creativecommons.org/licenses/by/4.0/).

    ?.

    E-mail address:huanyu.cheng@psu.edu(H.Cheng).

    亚洲一区二区三区不卡视频| 黄色 视频免费看| 黄色 视频免费看| 亚洲成人国产一区在线观看| 大型av网站在线播放| 国产区一区二久久| 午夜福利影视在线免费观看| 亚洲美女黄片视频| 亚洲性夜色夜夜综合| 一级作爱视频免费观看| 国精品久久久久久国模美| 在线观看www视频免费| 久久精品aⅴ一区二区三区四区| 中文字幕另类日韩欧美亚洲嫩草| 亚洲一区高清亚洲精品| 美女福利国产在线| 老汉色∧v一级毛片| 欧美老熟妇乱子伦牲交| 日韩大码丰满熟妇| 国内久久婷婷六月综合欲色啪| 欧美精品啪啪一区二区三区| 亚洲少妇的诱惑av| 天堂中文最新版在线下载| 很黄的视频免费| 午夜免费鲁丝| 欧美日韩亚洲高清精品| 成人免费观看视频高清| 美女 人体艺术 gogo| xxxhd国产人妻xxx| 每晚都被弄得嗷嗷叫到高潮| 亚洲av日韩精品久久久久久密| 亚洲一卡2卡3卡4卡5卡精品中文| 中文字幕av电影在线播放| 欧美日韩黄片免| 久久中文看片网| 亚洲五月天丁香| 亚洲第一欧美日韩一区二区三区| 9热在线视频观看99| 日本欧美视频一区| 久久久久久久久久久久大奶| 伦理电影免费视频| 在线观看www视频免费| 久久中文看片网| 十八禁人妻一区二区| 黄色丝袜av网址大全| 午夜激情av网站| avwww免费| 狠狠狠狠99中文字幕| 少妇的丰满在线观看| 香蕉久久夜色| 成年人午夜在线观看视频| 久久久久久久国产电影| 人人妻人人澡人人爽人人夜夜| 日韩有码中文字幕| 少妇猛男粗大的猛烈进出视频| 12—13女人毛片做爰片一| 99国产精品免费福利视频| 国产精华一区二区三区| 啦啦啦视频在线资源免费观看| 中文字幕制服av| 啦啦啦 在线观看视频| 69精品国产乱码久久久| 啦啦啦视频在线资源免费观看| 精品电影一区二区在线| 国产精品av久久久久免费| 很黄的视频免费| 韩国av一区二区三区四区| 国产在线一区二区三区精| 国产精品.久久久| 在线观看日韩欧美| 天天躁日日躁夜夜躁夜夜| 十八禁高潮呻吟视频| 黑丝袜美女国产一区| 极品人妻少妇av视频| 亚洲成人手机| 天天影视国产精品| 成在线人永久免费视频| 老司机福利观看| 亚洲国产精品合色在线| 亚洲精品一二三| 99riav亚洲国产免费| 国产aⅴ精品一区二区三区波| 亚洲中文字幕日韩| 日韩熟女老妇一区二区性免费视频| 黄色片一级片一级黄色片| 热re99久久国产66热| 日韩欧美国产一区二区入口| 狠狠狠狠99中文字幕| 美女扒开内裤让男人捅视频| 午夜两性在线视频| 深夜精品福利| 亚洲成a人片在线一区二区| 香蕉久久夜色| 久久精品熟女亚洲av麻豆精品| 欧美精品人与动牲交sv欧美| 成人18禁高潮啪啪吃奶动态图| 建设人人有责人人尽责人人享有的| 高清视频免费观看一区二区| 免费不卡黄色视频| 亚洲va日本ⅴa欧美va伊人久久| 精品国产一区二区三区四区第35| 久久久久国内视频| 91老司机精品| 日本五十路高清| 狠狠婷婷综合久久久久久88av| 久久草成人影院| 美女国产高潮福利片在线看| 在线免费观看的www视频| 午夜精品在线福利| 91九色精品人成在线观看| 久久国产乱子伦精品免费另类| 亚洲欧美一区二区三区黑人| 国产高清videossex| 激情视频va一区二区三区| 99re6热这里在线精品视频| 中文字幕人妻熟女乱码| 两性午夜刺激爽爽歪歪视频在线观看 | 久久久久国产一级毛片高清牌| 国产99久久九九免费精品| 在线观看免费高清a一片| 老司机午夜十八禁免费视频| 制服人妻中文乱码| 午夜91福利影院| 曰老女人黄片| 极品少妇高潮喷水抽搐| 国产xxxxx性猛交| 精品免费久久久久久久清纯 | 欧美不卡视频在线免费观看 | 亚洲avbb在线观看| 亚洲自偷自拍图片 自拍| 天天躁夜夜躁狠狠躁躁| 免费在线观看完整版高清| 久久久久久久精品吃奶| 国产单亲对白刺激| 亚洲精品av麻豆狂野| 变态另类成人亚洲欧美熟女 | 久久性视频一级片| 亚洲人成电影免费在线| 欧美日韩亚洲国产一区二区在线观看 | 中文字幕最新亚洲高清| 欧美日韩国产mv在线观看视频| 国产亚洲一区二区精品| 国产男靠女视频免费网站| 99热只有精品国产| 久久久久久久精品吃奶| 国产国语露脸激情在线看| 久久影院123| 水蜜桃什么品种好| 一进一出抽搐gif免费好疼 | 国产97色在线日韩免费| 国产亚洲av高清不卡| 亚洲精品粉嫩美女一区| 国产男女内射视频| 亚洲专区中文字幕在线| 亚洲黑人精品在线| 久久青草综合色| 村上凉子中文字幕在线| a在线观看视频网站| 99精品在免费线老司机午夜| 久久亚洲精品不卡| 三级毛片av免费| 欧美日韩瑟瑟在线播放| 欧美日本中文国产一区发布| 色综合欧美亚洲国产小说| 精品少妇一区二区三区视频日本电影| 成人亚洲精品一区在线观看| 久久ye,这里只有精品| ponron亚洲| 免费女性裸体啪啪无遮挡网站| 色尼玛亚洲综合影院| 老汉色∧v一级毛片| 99国产综合亚洲精品| 夫妻午夜视频| 国产精品影院久久| 午夜老司机福利片| 一二三四在线观看免费中文在| 91精品三级在线观看| av片东京热男人的天堂| 丰满饥渴人妻一区二区三| 亚洲av电影在线进入| 欧美另类亚洲清纯唯美| 老熟女久久久| 亚洲一区二区三区欧美精品| 啦啦啦在线免费观看视频4| 亚洲国产毛片av蜜桃av| 久久久国产成人免费| 国产成+人综合+亚洲专区| 热99久久久久精品小说推荐| 最新在线观看一区二区三区| 悠悠久久av| 国产伦人伦偷精品视频| 免费在线观看日本一区| 国产高清激情床上av| 别揉我奶头~嗯~啊~动态视频| 老司机深夜福利视频在线观看| 欧美午夜高清在线| 亚洲成国产人片在线观看| 日韩中文字幕欧美一区二区| 久久精品国产亚洲av高清一级| 黄片播放在线免费| 精品一品国产午夜福利视频| 99久久精品国产亚洲精品| 九色亚洲精品在线播放| 国产午夜精品久久久久久| 91麻豆av在线| 99久久人妻综合| 午夜福利在线观看吧| 国产1区2区3区精品| 午夜福利欧美成人| 亚洲欧美激情综合另类| 欧美日韩黄片免| 精品免费久久久久久久清纯 | 色94色欧美一区二区| 欧美中文综合在线视频| 新久久久久国产一级毛片| 久久天躁狠狠躁夜夜2o2o| 真人做人爱边吃奶动态| 欧美黑人精品巨大| 99久久精品国产亚洲精品| 久久香蕉精品热| 老司机影院毛片| 午夜久久久在线观看| 高清欧美精品videossex| 国产97色在线日韩免费| 久久九九热精品免费| 精品国产一区二区久久| 男女高潮啪啪啪动态图| 老司机在亚洲福利影院| 久久精品aⅴ一区二区三区四区| 久久国产精品大桥未久av| 三级毛片av免费| 热99国产精品久久久久久7| 人妻一区二区av| 久久久久国产一级毛片高清牌| 身体一侧抽搐| 中国美女看黄片| 亚洲av片天天在线观看| 精品人妻熟女毛片av久久网站| 中出人妻视频一区二区| 亚洲精品在线观看二区| 麻豆国产av国片精品| 欧美日韩瑟瑟在线播放| 欧美日韩亚洲综合一区二区三区_| 欧美大码av| 欧美av亚洲av综合av国产av| 国产熟女午夜一区二区三区| 国产精品亚洲一级av第二区| 黄频高清免费视频| 黑人操中国人逼视频| 亚洲av美国av| 国内久久婷婷六月综合欲色啪| av中文乱码字幕在线| 久久九九热精品免费| 欧美激情久久久久久爽电影 | 国产精品影院久久| 欧美日韩福利视频一区二区| 久热爱精品视频在线9| 成在线人永久免费视频| 国产成人免费无遮挡视频| 亚洲精品久久成人aⅴ小说| 午夜老司机福利片| 亚洲三区欧美一区| a级毛片在线看网站| 精品久久久精品久久久| 一二三四社区在线视频社区8| 婷婷丁香在线五月| 精品亚洲成国产av| 性少妇av在线| 亚洲专区中文字幕在线| 久久久国产成人免费| 亚洲欧美精品综合一区二区三区| 精品国产乱码久久久久久男人| 国产99久久九九免费精品| 80岁老熟妇乱子伦牲交| 美女扒开内裤让男人捅视频| 巨乳人妻的诱惑在线观看| 69精品国产乱码久久久| 侵犯人妻中文字幕一二三四区| 中文字幕人妻丝袜制服| netflix在线观看网站| 亚洲av美国av| av天堂久久9| 99re在线观看精品视频| 久久草成人影院| 好男人电影高清在线观看| 欧美亚洲 丝袜 人妻 在线| 老司机亚洲免费影院| 欧美日韩中文字幕国产精品一区二区三区 | 日本精品一区二区三区蜜桃| 搡老乐熟女国产| 国产又色又爽无遮挡免费看| 欧美一级毛片孕妇| 国产在线观看jvid| 18禁裸乳无遮挡动漫免费视频| 久久久久久久国产电影| av福利片在线| 老司机靠b影院| 在线观看午夜福利视频| 欧美不卡视频在线免费观看 | 少妇的丰满在线观看| 伊人久久大香线蕉亚洲五| 91国产中文字幕| 国产精品99久久99久久久不卡| 日韩欧美免费精品| 在线国产一区二区在线| 成人亚洲精品一区在线观看| 精品高清国产在线一区| 欧美激情极品国产一区二区三区| 久久影院123| 久久亚洲精品不卡| 亚洲成国产人片在线观看| 丝瓜视频免费看黄片| 久9热在线精品视频| 一边摸一边做爽爽视频免费| 18在线观看网站| 欧美精品亚洲一区二区| av网站免费在线观看视频| 国产成+人综合+亚洲专区| 成人亚洲精品一区在线观看| 一区二区三区国产精品乱码| av有码第一页| 男男h啪啪无遮挡| 99精品欧美一区二区三区四区| 黑人猛操日本美女一级片| 日本欧美视频一区| 亚洲综合色网址| 极品少妇高潮喷水抽搐| 99久久精品国产亚洲精品| 91字幕亚洲| 后天国语完整版免费观看| 一级黄色大片毛片| 1024视频免费在线观看| 黄色成人免费大全| 1024视频免费在线观看| 女同久久另类99精品国产91| 久久婷婷成人综合色麻豆| 久久中文字幕一级| 91在线观看av| 久久人妻福利社区极品人妻图片| 午夜福利影视在线免费观看| 国产男女超爽视频在线观看| 亚洲欧美一区二区三区久久| 国产一区二区三区在线臀色熟女 | 午夜精品国产一区二区电影| 中文字幕人妻熟女乱码| 女人被躁到高潮嗷嗷叫费观| 亚洲一卡2卡3卡4卡5卡精品中文| ponron亚洲| 青草久久国产| 中文亚洲av片在线观看爽 | 欧美亚洲日本最大视频资源| 久久性视频一级片| 动漫黄色视频在线观看| 亚洲色图 男人天堂 中文字幕| 日本黄色视频三级网站网址 | 韩国精品一区二区三区| 制服诱惑二区| 亚洲成人免费电影在线观看| 高清毛片免费观看视频网站 | 男人舔女人的私密视频| x7x7x7水蜜桃| 极品少妇高潮喷水抽搐| e午夜精品久久久久久久| 国产精品99久久99久久久不卡| 一夜夜www| 国产精品久久久久成人av| 亚洲av电影在线进入| 国产成人精品久久二区二区免费| 露出奶头的视频| 男男h啪啪无遮挡| 久久精品人人爽人人爽视色| 91在线观看av| 天堂中文最新版在线下载| 中文字幕精品免费在线观看视频| 狠狠狠狠99中文字幕| 免费日韩欧美在线观看| 免费人成视频x8x8入口观看| 777久久人妻少妇嫩草av网站| 狠狠狠狠99中文字幕| www日本在线高清视频| 最近最新中文字幕大全免费视频| 水蜜桃什么品种好| 99riav亚洲国产免费| 中文亚洲av片在线观看爽 | 日韩免费av在线播放| 波多野结衣一区麻豆| 美女视频免费永久观看网站| 99热国产这里只有精品6| 精品电影一区二区在线| 99热网站在线观看| 日本欧美视频一区| 国产精品永久免费网站| 一本一本久久a久久精品综合妖精| 国产精品一区二区在线不卡| 99精品欧美一区二区三区四区| 午夜免费鲁丝| 国产免费现黄频在线看| 国产亚洲精品一区二区www | 国产精品久久久久久精品古装| 欧美日韩视频精品一区| 日韩制服丝袜自拍偷拍| 免费不卡黄色视频| 精品一区二区三卡| 国产人伦9x9x在线观看| 捣出白浆h1v1| 午夜日韩欧美国产| 精品免费久久久久久久清纯 | 一区在线观看完整版| 又紧又爽又黄一区二区| 亚洲第一av免费看| 三上悠亚av全集在线观看| 免费女性裸体啪啪无遮挡网站| 天天躁日日躁夜夜躁夜夜| 国产蜜桃级精品一区二区三区 | 热re99久久精品国产66热6| 免费人成视频x8x8入口观看| 两性午夜刺激爽爽歪歪视频在线观看 | tocl精华| 超碰成人久久| 国产免费现黄频在线看| 黑人欧美特级aaaaaa片| 天天影视国产精品| 精品国产一区二区久久| 亚洲中文字幕日韩| 久久久久久久精品吃奶| 91在线观看av| 老汉色av国产亚洲站长工具| 成人18禁在线播放| 亚洲国产精品sss在线观看 | cao死你这个sao货| 香蕉久久夜色| av有码第一页| 亚洲欧美日韩高清在线视频| 国产欧美日韩一区二区三| 久久久久国产一级毛片高清牌| 天天躁夜夜躁狠狠躁躁| 久久久精品国产亚洲av高清涩受| 丁香欧美五月| 国内久久婷婷六月综合欲色啪| 精品乱码久久久久久99久播| 真人做人爱边吃奶动态| 欧美日韩亚洲综合一区二区三区_| www日本在线高清视频| 色精品久久人妻99蜜桃| 亚洲国产欧美日韩在线播放| 国产亚洲欧美98| 午夜福利欧美成人| 久久热在线av| 久久久国产精品麻豆| 又黄又粗又硬又大视频| 最近最新免费中文字幕在线| 欧美亚洲日本最大视频资源| 免费不卡黄色视频| 久久精品aⅴ一区二区三区四区| 狠狠狠狠99中文字幕| 欧美日韩瑟瑟在线播放| 一区二区三区精品91| 三上悠亚av全集在线观看| 国产97色在线日韩免费| 久久精品国产亚洲av香蕉五月 | 午夜福利在线免费观看网站| 成年人午夜在线观看视频| 最新的欧美精品一区二区| 国产高清视频在线播放一区| 久久精品国产99精品国产亚洲性色 | 久久ye,这里只有精品| 老汉色av国产亚洲站长工具| 一本综合久久免费| 免费看十八禁软件| 大型黄色视频在线免费观看| 精品午夜福利视频在线观看一区| 久久天堂一区二区三区四区| 久久国产亚洲av麻豆专区| 久久中文字幕一级| 在线观看免费视频日本深夜| 99热国产这里只有精品6| 在线视频色国产色| 国产高清videossex| 亚洲精品粉嫩美女一区| 热99国产精品久久久久久7| 丝袜人妻中文字幕| 丝瓜视频免费看黄片| 色综合欧美亚洲国产小说| 欧美激情 高清一区二区三区| 丁香六月欧美| 亚洲精品中文字幕一二三四区| 国产视频一区二区在线看| 别揉我奶头~嗯~啊~动态视频| 午夜福利视频在线观看免费| 国产高清videossex| 亚洲中文av在线| 中文字幕精品免费在线观看视频| 丝袜人妻中文字幕| 亚洲伊人色综图| 熟女少妇亚洲综合色aaa.| 精品乱码久久久久久99久播| 99久久99久久久精品蜜桃| 交换朋友夫妻互换小说| 12—13女人毛片做爰片一| 久久久国产成人精品二区 | 亚洲精品自拍成人| 欧美+亚洲+日韩+国产| 老司机福利观看| 高清视频免费观看一区二区| av电影中文网址| 母亲3免费完整高清在线观看| 日韩中文字幕欧美一区二区| 色婷婷av一区二区三区视频| 在线永久观看黄色视频| 丁香六月欧美| 精品福利永久在线观看| 欧美精品啪啪一区二区三区| 一夜夜www| 色婷婷久久久亚洲欧美| 69av精品久久久久久| 又黄又粗又硬又大视频| 狠狠婷婷综合久久久久久88av| 在线观看免费视频日本深夜| 国产麻豆69| 两个人免费观看高清视频| 久久青草综合色| 亚洲精品中文字幕一二三四区| 日本黄色视频三级网站网址 | 在线永久观看黄色视频| 热re99久久国产66热| 亚洲国产欧美一区二区综合| 亚洲 国产 在线| 午夜久久久在线观看| 岛国毛片在线播放| 成年版毛片免费区| 18禁黄网站禁片午夜丰满| 一a级毛片在线观看| 亚洲精品久久午夜乱码| 亚洲国产精品一区二区三区在线| 欧美亚洲日本最大视频资源| 自拍欧美九色日韩亚洲蝌蚪91| 亚洲男人天堂网一区| 搡老熟女国产l中国老女人| 国产黄色免费在线视频| 老熟女久久久| 搡老乐熟女国产| 99精国产麻豆久久婷婷| 午夜两性在线视频| 在线av久久热| 亚洲成av片中文字幕在线观看| 老司机深夜福利视频在线观看| 中文欧美无线码| 在线视频色国产色| 亚洲精品久久午夜乱码| 99国产精品一区二区蜜桃av | 亚洲欧美激情综合另类| 18禁国产床啪视频网站| 亚洲专区字幕在线| 制服诱惑二区| 精品国产一区二区三区四区第35| 99精品在免费线老司机午夜| 精品福利永久在线观看| 欧美+亚洲+日韩+国产| av一本久久久久| 国产av精品麻豆| 亚洲中文字幕日韩| 久久精品国产99精品国产亚洲性色 | 美女福利国产在线| 免费看十八禁软件| 亚洲美女黄片视频| 人妻丰满熟妇av一区二区三区 | 黑人操中国人逼视频| 日韩大码丰满熟妇| 天天躁狠狠躁夜夜躁狠狠躁| 久久人妻av系列| 国产一区二区激情短视频| 香蕉久久夜色| 电影成人av| av免费在线观看网站| 国产精品久久视频播放| 国产亚洲一区二区精品| 别揉我奶头~嗯~啊~动态视频| 国产成人欧美| 18禁黄网站禁片午夜丰满| 亚洲美女黄片视频| 国产精品久久电影中文字幕 | 成年人黄色毛片网站| 一进一出抽搐gif免费好疼 | 熟女少妇亚洲综合色aaa.| 午夜免费观看网址| 日日摸夜夜添夜夜添小说| 久久中文字幕一级| 777久久人妻少妇嫩草av网站| 大香蕉久久成人网| 好男人电影高清在线观看| 少妇的丰满在线观看| 午夜福利一区二区在线看| 91老司机精品| 国产一区二区三区在线臀色熟女 | 一二三四在线观看免费中文在| 久久九九热精品免费| 日韩欧美国产一区二区入口| 国产成人欧美在线观看 | 久久精品亚洲熟妇少妇任你| 中文字幕人妻熟女乱码| 国产蜜桃级精品一区二区三区 | 最新的欧美精品一区二区| 国产一区有黄有色的免费视频| 日日爽夜夜爽网站| 丝袜人妻中文字幕| 亚洲第一av免费看| 一区二区三区国产精品乱码| 国产精品偷伦视频观看了| av在线播放免费不卡| 91在线观看av| tocl精华| 国产av一区二区精品久久| 美国免费a级毛片| 一级作爱视频免费观看| 久久天堂一区二区三区四区|