• <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 ?

    Modelling drying pathways of an evaporating soft matter droplet

    2022-10-22 08:15:26GuangleDuFangfuYeHaoLuoGuangyinJingMasaoDoiandFanlongMeng
    Communications in Theoretical Physics 2022年9期

    Guangle Du,Fangfu Ye,Hao Luo,Guangyin Jing,Masao Doi and Fanlong Meng

    1 CAS Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190,China

    2 Wenzhou Institute,University of Chinese Academy of Sciences,Wenzhou 325001,China

    3 School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China

    4 Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China

    5 Songshan Lake Materials Laboratory,Dongguan 523808,China

    6 School of Physics,and State Key Laboratory of Photon-Technology in Western China Energy,Northwest University,Xi’an 710069,China

    7 Center of Soft Matter Physics and its Applications,Beihang University,Beijing 100191,China

    Abstract Micro-droplets of soft matter solutions have different morphologies upon drying,and can become wrinkled,buckled or cavitated particles.We investigate the morphology evolution of a drying soft matter droplet in this work:at the early stage of drying,wrinkling or cavitation instability can occur in the droplet,depending on the comparison between the critical wrinkling and cavitation pressure;at a later stage of drying,no wrinkles will appear if cavitation happens first,while cavitation can still occur if wrinkling happens first.A three-dimensional phase diagram in the space of elastic length,gel layer thickness and weight loss is provided to illustrate the drying pathways of a soft matter droplet.This diagram can help guide future fabrications of micro-particles with desired morphologies.

    Keywords: soft matter solution,drying,instabilities

    A soft matter droplet consisting of polymer solutions or colloidal dispersions can exhibit different morphologies such as buckling[1–4],wrinkling[5–8],or cavitation[9–12]during the drying process.When all solvents evaporate,the soft matter droplets can turn out to be solid,hollow,wrinkled or buckled particles as the final products [13–17].This drying process,especially spray drying,has been widely utilised to produce micro-particles of different morphologies in industrial circumstances such as food or pharmaceutical particle production[17–21],amorphous material crystallisation[22–24],functional encapsulated particle manufacture[25–27],etc.,where different shapes are achieved by empirically changing the drying temperature,concentration and constitution of the soft matter solution [3,28–36].

    In the drying process of a soft matter droplet,the competition of solute advection towards the droplet surface as the deposition due to drying and solute diffusion homogenising the solute concentration is captured by the Péclet number.When the Péclet number is sufficiently large,the solution at the outmost layer of the droplet can solidify to become a gel-like layer[16,37–39],which grows with time.This gel layer has been believed to relate to the morphology evolution and the final configurations of drying soft matter droplets [12,33,40–42].However,how the properties of the gel layer can determine the drying process of the soft matter droplet still remains unclear.

    In this work,we will study how the morphology of a drying soft matter droplet can evolve with time depending on the physical properties of the gel layer such as its elasticity and dimension,by considering the prepared state of the droplet as a spherical core–shell structured system as in spray drying(shown in figure 1).The core will be simply regarded as liquid,whose amount decreases continuously due to solvent evaporation;the shell(skin layer)will be treated with non-evolving elastic properties and thickness for simplicity,as the evolution of the skin layer,such as mass growth from further diffusion and deposition of the solute,would not change the results qualitatively.By taking these simplifications,we can construct the analytical energy form of the system,and then discuss the morphology evolution of the drying soft matter droplet.

    Figure 1.Drying pathways of an evaporating soft matter droplet.

    Compared to solvent evaporation,the mechanically equilibrating process of the gel layer is a fast process;in other words,we can use the mass loss of the droplet due to evaporation,ΔW=W0-W,as the controllable variable of the system,where W0and W denote the initial and current mass of the droplet,respectively.Then we can discuss the morphology evolution of the droplet by optimising the total free energy of the system under given ΔW.By taking the initial radius of the droplet as R0,and the radius of the cavity as Rc[reduced cavity volumevc≡(RcR0)3],the volume of the droplet can be expressed asfrom volume conservation.The total Gibbs free energy of the system can be written as

    where γ denotes the interfacial tension between the cavity and the fluid,Δpol=po-pland Δplc=pl-pc,with po~105Pa,pland pcas the pressure of the outside,the liquid and the cavity,respectively.The pressure of the cavity can be expressed as8See supplementary materials available online at stacks.iop.org/CTP/74/095605/mmedia.where vlis the volume of a single liquid molecule,PL(x)is the principal branch of Lambert W function and peqis the bulk vapor pressure.Taking typical values of vl~10-29m3and peq~105Pa,we have peqvl/(kBT)~10-3,and then the pressure in the cavity can be approximated bypc≈peqexp [-2γ vl/(RckBT)].In equation(1),the first term on the right-hand-side(RHS)denotes the interfacial energy of the interface between the cavity and the liquid,the second term denotes the work done by the pressure difference between the liquid and the cavity,and the last term denotes the elastic energy of the gel layer.In the last term,Eαβand Kαβare the stretching and the bending strains,respectively,Nαβand Mαβare the stretching stress and the bending moment,respectively,w is the normal displacement along the radial direction of the gel layer.Note that the normal displacement is taken as positive if it is pointing towards the droplet centre.Here we adopt the Donnell–Mushtari–Vlasov (DMV) strain-displacement relations,which are valid for small deformations,as Eαβ=(?βuα+?αuβ)/2-bαβw+?αw ?βw/2 and Kαβ=?α?βw,where ?is covariant derivative,uαis the tangential displacement along α direction and bαβis curvature tensor of the gel layer shell [43].The stretching stress Nαβand the bending moment Mαβcan be expressed as functions of the strain tensors:Nαβ=Eh[(1-ν)Eαβ+νgαβEγγ]/(1-ν2) andMαβ=Eh3[(1-ν)Kαβ+νgαβKγγ]/[12 (1-ν2)],with gαβbeing the metric tensor of the shell surface,and h,E and ν being the thickness,Young’s modulus and the Poisson ratio of the gel layer,respectively [43].

    Critical wrinkling pressure.The gel layer can wrinkle or buckle during the drying process,and we first discuss the criterion of when wrinkling or buckling can occur on the surface of the droplet.If there is no cavity,the total energy reduces to the purely elastic one (last term on the RHS of equation (1)).To obtain the critical wrinkling pressure,we perform the linear instability analysis on the Euler–Lagrange (EL) equations obtained from the variation of the elastic energy functional(see footnote 8).The uniform solution of the EL equations is uφ=uθ=0,w0=(1-ν) ΔpolR02/(2Eh),which represents the uniform contraction of the gel layer under the pressure difference between the outside and the liquid Δpol.By adding a small perturbation w1to the uniform normal displacement,i.e.,w=w0+w1and introducing a small perturbation χ1in the Airy stress function [43],we can obtain

    after keeping terms up to the linear order in the EL equations.By expressing w1and χ1with spherical harmonicsYlm(φ,θ)(eigenmodes of Laplace operator),asw1=AYlmandχ1=BYlm,then from equation (2) we can obtain the possible eigenmodes denoted by l as a function of the pressure Δpol,

    where D=Eh3/[12(1-ν2)].The minimal pressure Δpoldenoted by *pwto have a real and positive l(l+1),i.e.,the critical pressure leading to wrinkling,is [43]

    It is clear that the gel layer can easily wrinkle if it is soft(small Young’s modulus) and the thickness is small compared to the droplet size.If there is a ring-like defect with a smaller Young’s modulus in the gel layer,then buckling can easily occur and the corresponding buckling pressure can be obtained by shallow shell approximation,which gives the same value as the critical wrinkling pressure *pw(See footnote 8).Note this critical wrinkling pressure is obtained for a perfect sphere and is sensitive to imperfections [44,45].If imperfections are present in shell possibly due to density inhomogeneity [46],orthotropic elasticity [47],etc.,the critical wrinkling pressure can drop considerably by an empirical proportion.Nevertheless,the above critical wrinkling pressure can still dominate the wrinkling behavior.In the following discussions,we use the term‘wrinkling instability’ to denote both wrinkling and buckling instability without losing generality.

    Critical cavitation pressure.There is a critical cavitation pressure *pcif there is no wrinkling.In this case,the elastic energy of the gel layer is simplyFelastic=12πhKew02[41],where Ke=E/[3(1-ν)]is the effective elastic modulus.After the insertion of the mass conservation relation,the total Gibbs free energy of the system is

    where Δpoc=po-pc.The critical point for the above total Gibbs free energy to have a non-zero local minimum point is determined by ?Ftot/?vc=0 and Ftot(vc)=Ftot(0),from which we can obtain the critical cavity volume asvc*=[le(2h)]3/4with the elastic length defined by le≡2γ/Keand the critical weight loss for cavitation as[41].Utilisation of the mass conservation under uniform contraction with no cavity gives the relation between the pressure and the weight loss Δpol=2hKe/R0·ΔW/W0.Then the critical cavitation pressure,i.e.,the minimal pressure Δpoldenoted by*pcto have cavity,is

    By comparing the critical wrinkling pressure *pwand the critical cavitation pressure *pc,we can obtain the criterion for wrinkling happening ahead of the droplet cavitation at an early stage of the drying process,written explicitly as

    otherwise,cavitation occurs first.In other words,if the gel layer is thin and soft,the droplet tends to wrinkle at the surface.More importantly,such divergence in the instabilities at the early stage of the drying process leads to different drying pathways and can determine the final morphology of the drying droplet as discussed below.

    Drying pathway–no wrinkling after cavitation.We investigate whether wrinkling still occurs if cavitation happens first.As shown in the inset of figure 2(b),Δpolconstantly increases before cavitation and becomesafter cavitation.At the critical cavitation point,which is smaller than the critical cavitation pressure *pc.Meanwhile,the first derivative of Δpolafter cavitation with regards to the weight loss,?Δpol/?ΔW=-2γ/(R0W0)means that Δpoldecreases further with increasing weight loss ΔW.This indicates that no wrinkling can happen after cavitation since the critical wrinkling pressure can not be reached any more [drying pathway in figure 1 as (a)→(b)→(c1)→(c2)].

    Drying pathway–cavitation after wrinkling.We proceed to investigate whether the cavity can still form if wrinkling occurs first.By assuming the wrinkles as a perturbation with the form of a spherical harmonic mode and assuming that the perturbation amplitude is small,then the Helmholtz free energy can be expressed in the same form as that in equation (5),but with a modified effective elastic modulus(see footnote 8)

    whereA′=A/his the ratio of the perturbation amplitude over the gel layer thickness.Then it is clear that cavitation can still happen after wrinkling,with the critical weight loss for cavitation aswhereis the new elastic length.Meanwhile,the effective elastic modulusKe′ is smaller than the one without wrinkling Ke,resulting in a larger value of the critical weight loss than that in the case without wrinkling.Note that according to the previous discussion,the pressure difference between the outside and the liquid Δpoldrops at cavitation and decreases after cavitation with the increase of weight loss (see inset of figure 2(b)),thus the wrinkles may disappear due to the decrease of Δpol.However,in a practical drying process,the formed wrinkles of the gel layer can become rigid,e.g.turn glassy [40],and the decrease of Δpolinduced by the cavitation is not high enough to flatten the wrinkles on the gel layer with increased rigidity.In this case,the wrinkles can still remain regardless of the decrease of the pressure difference between the outside and the liquid after cavitation (drying pathway in figure 1 as(a)→(b)→(d1)→(d2)).Note that the gel layer can still be permeable to solvents despite its rigidification,and the subsequent evaporation and cavity enlargement are not hindered.

    In figure 2(a),a 3D phase diagram summarising the above discussions of the drying pathways of a soft matter droplet is provided in the space of elastic length,gel layer thickness and weight loss,together with its two cross sections of a given fixed elastic length in figure 2(b) and of a given fixed thickness in figure 2(c),respectively.Note that the weight loss in the phase diagram can play the role of time if the evaporation rate of the droplet is known [39,48].At the early stage of the drying process,i.e.,when ΔW is small,either wrinkling or cavitation instability can occur,resulting from the competition between the surface energy of the cavity,and the bending and stretching elastic energy of the gel layer.When the gel layer is thin and soft(small h and small Ke(large le)),then wrinkling occurs,which is obvious in figure 2(b) and figure 2(c);otherwise,cavitation happens.Meanwhile,the choice in either wrinkling or cavitation instability at the early stage of the drying process,determines the later morphology evolution and the final product of the drying soft matter droplet: (a) if wrinkling takes place ahead of the cavitation,then there will still be cavity formed in the droplet with the ongoing evaporation of the solvents and the final configuration of the drying droplet will be a hollow and wrinkled particle;(b)if cavitation happens first,then there will be no wrinkling in the later drying process due to the decreasing pressure difference between the outside and the droplet,and a spherical shell is left after finishing the whole evaporation process.

    Figure 2.(a)3D phase diagram with three dimensionless varying variables,i.e.,elastic length over shell thickness le/h,shell thickness over initial droplet radius h/R0,and the reduced weight loss of the droplet ΔW/W0.Here Poisson ratio ν=0.5.(b) Cross section of 3D phase diagram with fixed le/h=0.037.Inset: the pressure difference between the outside and the liquid is smaller than the critical cavitation pressure and constantly decreases after cavitation,impeding the occurrence of wrinkling.In the inset,le/h=0.1.(c) Cross section of 3D phase diagram with fixed h/R0=0.2.

    We investigate here how the morphology of a drying soft matter droplet can evolve with time based on a pseudo-dynamic analysis.The elastic properties of the gel layer formed at the surface of the soft matter droplet play a key role in determining the drying pathways of the droplet,including both the instabilities triggered at the early stage of the drying process,the later morphology evolution,and the final configurations.A quasiequilibrium treatment is taken for discussing how morphology of a droplet evolves with time by performing energy minimisation,which at certain conditions should be revised,e.g.,if the evaporation is fast where sub-processes such as solute diffusion,gel-layer formation,etc occur at a comparable time scale as solvent evaporation.Regardless of the simplifications for analytic discussions in this work,we believe this portable model has captured the essential physics underlying the morphology evolution of a drying soft matter droplet,which can guide the industrial fabrications of micro-particles with desired morphologies and functions.

    Acknowledgments

    F M acknowledges supports from Chinese Academy of Sciences (No.XDA17010504 and No.XDPB15),and the National Natural Science Foundation of China (No.12 047 503).F Y acknowledges the support of the National Natural Science Foundation of China(Grant No.11 774 394)and the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDB-SSW-SYS003).G D thanks Xiao Lin for fruitful discussions.

    ORCID iDs

    国产精品98久久久久久宅男小说| 午夜久久久久精精品| 亚洲av免费在线观看| 国产精品久久久人人做人人爽| 丰满人妻一区二区三区视频av | 亚洲,欧美精品.| 搡老妇女老女人老熟妇| 男女那种视频在线观看| 中文字幕熟女人妻在线| 亚洲av五月六月丁香网| 久久精品亚洲精品国产色婷小说| 国产精品电影一区二区三区| 国产激情偷乱视频一区二区| 久久精品亚洲精品国产色婷小说| 在线国产一区二区在线| 成人精品一区二区免费| 成人一区二区视频在线观看| a级一级毛片免费在线观看| 无限看片的www在线观看| 免费看日本二区| 亚洲精品乱码久久久v下载方式 | 动漫黄色视频在线观看| 久久精品人妻少妇| 亚洲中文字幕一区二区三区有码在线看| 小说图片视频综合网站| 悠悠久久av| 亚洲真实伦在线观看| 精品一区二区三区视频在线观看免费| 国产爱豆传媒在线观看| av天堂中文字幕网| 久久国产精品影院| 在线播放无遮挡| 日本熟妇午夜| 欧美+日韩+精品| 老司机深夜福利视频在线观看| 国产精品99久久99久久久不卡| 国产精品久久久久久久电影 | 一个人免费在线观看电影| 欧美在线一区亚洲| 日韩欧美三级三区| 黄片小视频在线播放| 五月玫瑰六月丁香| 久久香蕉国产精品| 综合色av麻豆| 久久久久久久午夜电影| 国产一区二区三区在线臀色熟女| 听说在线观看完整版免费高清| 国产精品女同一区二区软件 | 91在线观看av| 国产精品国产高清国产av| 婷婷精品国产亚洲av| 动漫黄色视频在线观看| 一区二区三区高清视频在线| 成人国产一区最新在线观看| 亚洲精品在线观看二区| 色在线成人网| 国产不卡一卡二| 精品国产美女av久久久久小说| 男女做爰动态图高潮gif福利片| 少妇丰满av| 国产精品久久久久久精品电影| 十八禁网站免费在线| 国产黄a三级三级三级人| 舔av片在线| 一夜夜www| 观看美女的网站| 亚洲五月天丁香| 黄片大片在线免费观看| 久久九九热精品免费| 1024手机看黄色片| 成人午夜高清在线视频| 黄色视频,在线免费观看| 欧美成人一区二区免费高清观看| 18禁黄网站禁片午夜丰满| 99热6这里只有精品| www国产在线视频色| 在线播放国产精品三级| 脱女人内裤的视频| 国产精品亚洲美女久久久| 欧美日韩精品网址| 小说图片视频综合网站| 12—13女人毛片做爰片一| 久久久久亚洲av毛片大全| 2021天堂中文幕一二区在线观| eeuss影院久久| 91麻豆精品激情在线观看国产| 国产成人福利小说| 极品教师在线免费播放| 99国产精品一区二区蜜桃av| 一本久久中文字幕| 三级毛片av免费| 特大巨黑吊av在线直播| 制服人妻中文乱码| 亚洲中文日韩欧美视频| 国产探花极品一区二区| 国产黄片美女视频| 成人特级黄色片久久久久久久| 欧美+亚洲+日韩+国产| 伊人久久大香线蕉亚洲五| 日本与韩国留学比较| 欧美av亚洲av综合av国产av| 宅男免费午夜| 嫩草影院精品99| 俄罗斯特黄特色一大片| 亚洲人成网站在线播放欧美日韩| h日本视频在线播放| e午夜精品久久久久久久| 午夜福利在线观看吧| 男人和女人高潮做爰伦理| 99热6这里只有精品| 人妻久久中文字幕网| 国产精品久久电影中文字幕| 精品无人区乱码1区二区| 内地一区二区视频在线| 天堂网av新在线| 香蕉久久夜色| 在线a可以看的网站| 午夜影院日韩av| 久久久成人免费电影| a级毛片a级免费在线| 女人十人毛片免费观看3o分钟| 亚洲精品久久国产高清桃花| 非洲黑人性xxxx精品又粗又长| 午夜久久久久精精品| 亚洲午夜理论影院| 国产精品98久久久久久宅男小说| 成人av一区二区三区在线看| 亚洲片人在线观看| 一进一出好大好爽视频| 一二三四社区在线视频社区8| 嫩草影院精品99| 啪啪无遮挡十八禁网站| 欧美成狂野欧美在线观看| av片东京热男人的天堂| 亚洲第一电影网av| 亚洲国产欧美网| 在线观看免费视频日本深夜| 成人三级黄色视频| 日韩欧美三级三区| 免费大片18禁| 一本久久中文字幕| 蜜桃亚洲精品一区二区三区| 国产 一区 欧美 日韩| 国产欧美日韩精品一区二区| 免费av观看视频| 黄色成人免费大全| 国产精品影院久久| 久久中文看片网| 超碰av人人做人人爽久久 | 天堂√8在线中文| 欧美一区二区国产精品久久精品| 长腿黑丝高跟| 欧美性感艳星| 久久午夜亚洲精品久久| 久久久国产成人精品二区| 亚洲欧美日韩高清在线视频| 国产成+人综合+亚洲专区| 夜夜看夜夜爽夜夜摸| 精华霜和精华液先用哪个| 男女床上黄色一级片免费看| 亚洲aⅴ乱码一区二区在线播放| 18禁裸乳无遮挡免费网站照片| 亚洲欧美激情综合另类| 黑人欧美特级aaaaaa片| 国内精品一区二区在线观看| 亚洲电影在线观看av| 国产男靠女视频免费网站| 国产欧美日韩一区二区三| 欧美性感艳星| 禁无遮挡网站| 丰满人妻熟妇乱又伦精品不卡| 午夜免费男女啪啪视频观看 | 成人一区二区视频在线观看| 在线播放无遮挡| 国产99白浆流出| 婷婷六月久久综合丁香| 亚洲精品粉嫩美女一区| 少妇裸体淫交视频免费看高清| 国产欧美日韩一区二区精品| 亚洲一区高清亚洲精品| 看黄色毛片网站| 国产99白浆流出| 高清日韩中文字幕在线| 男女之事视频高清在线观看| 久9热在线精品视频| 中文在线观看免费www的网站| 天天一区二区日本电影三级| 又粗又爽又猛毛片免费看| 精品国产美女av久久久久小说| 18禁在线播放成人免费| 男人和女人高潮做爰伦理| 精品午夜福利视频在线观看一区| 99热精品在线国产| www日本在线高清视频| 少妇人妻一区二区三区视频| 国产黄a三级三级三级人| 精品久久久久久久末码| 国内精品久久久久久久电影| 久久久久精品国产欧美久久久| 天天一区二区日本电影三级| 亚洲精品亚洲一区二区| 久久亚洲精品不卡| 超碰av人人做人人爽久久 | 成人18禁在线播放| 亚洲国产日韩欧美精品在线观看 | 久久久久国内视频| 国产成人aa在线观看| 最新美女视频免费是黄的| 日本熟妇午夜| 91av网一区二区| 搡女人真爽免费视频火全软件 | 成人亚洲精品av一区二区| 日韩欧美在线二视频| 国产亚洲精品av在线| 女同久久另类99精品国产91| 精华霜和精华液先用哪个| 香蕉丝袜av| 国产麻豆成人av免费视频| 99精品在免费线老司机午夜| 一进一出抽搐gif免费好疼| 国产私拍福利视频在线观看| 俺也久久电影网| 国产精品永久免费网站| 岛国在线观看网站| 少妇人妻精品综合一区二区 | 午夜激情欧美在线| 国产成人a区在线观看| 小说图片视频综合网站| 国产精品av视频在线免费观看| 欧美性猛交╳xxx乱大交人| 真人一进一出gif抽搐免费| 欧美另类亚洲清纯唯美| 少妇的逼水好多| 久久久久久人人人人人| 老汉色av国产亚洲站长工具| 久久亚洲真实| 狂野欧美激情性xxxx| 免费一级毛片在线播放高清视频| 亚洲一区二区三区色噜噜| 国产精品久久久人人做人人爽| 18美女黄网站色大片免费观看| 精品久久久久久成人av| 麻豆成人午夜福利视频| 亚洲成av人片免费观看| 高清在线国产一区| 成人特级av手机在线观看| 国产成人系列免费观看| 精品久久久久久久人妻蜜臀av| av天堂中文字幕网| 亚洲精品一区av在线观看| 九色成人免费人妻av| 男人和女人高潮做爰伦理| a级一级毛片免费在线观看| 国产免费一级a男人的天堂| 高清日韩中文字幕在线| 成人无遮挡网站| 欧洲精品卡2卡3卡4卡5卡区| 欧美日韩精品网址| 亚洲成人中文字幕在线播放| 免费观看人在逋| 亚洲一区高清亚洲精品| 91在线观看av| 午夜福利在线在线| 男女床上黄色一级片免费看| 一本一本综合久久| 国内精品久久久久精免费| 国产99白浆流出| 午夜免费观看网址| 18美女黄网站色大片免费观看| 国产久久久一区二区三区| 成年版毛片免费区| 国产蜜桃级精品一区二区三区| 久久6这里有精品| 校园春色视频在线观看| 国产熟女xx| 少妇人妻一区二区三区视频| 日本免费a在线| 老司机午夜十八禁免费视频| 18+在线观看网站| 好男人电影高清在线观看| 久久久久久久午夜电影| 精品熟女少妇八av免费久了| 欧美高清成人免费视频www| 亚洲欧美日韩无卡精品| 性色av乱码一区二区三区2| 国产中年淑女户外野战色| 特大巨黑吊av在线直播| 九色国产91popny在线| 9191精品国产免费久久| 国产精品乱码一区二三区的特点| 国语自产精品视频在线第100页| 熟女电影av网| 又粗又爽又猛毛片免费看| 精品国产三级普通话版| 99热只有精品国产| 丰满乱子伦码专区| 男女之事视频高清在线观看| 久久亚洲真实| 一级作爱视频免费观看| 国产精品 欧美亚洲| 99精品在免费线老司机午夜| 国产毛片a区久久久久| 午夜两性在线视频| 国产三级在线视频| 色吧在线观看| 亚洲国产精品成人综合色| 亚洲在线观看片| 婷婷精品国产亚洲av在线| 99国产综合亚洲精品| 国产精品久久久久久久久免 | 18禁裸乳无遮挡免费网站照片| 国产在视频线在精品| 欧美区成人在线视频| АⅤ资源中文在线天堂| 黄色片一级片一级黄色片| 午夜视频国产福利| 国产野战对白在线观看| 精品免费久久久久久久清纯| 丰满人妻熟妇乱又伦精品不卡| 夜夜看夜夜爽夜夜摸| 中文字幕熟女人妻在线| 色av中文字幕| 黄色日韩在线| 国产亚洲欧美在线一区二区| 国产精品久久久久久久久免 | 看黄色毛片网站| 美女免费视频网站| 免费人成视频x8x8入口观看| 久久伊人香网站| 欧美日韩黄片免| a级毛片a级免费在线| 国产成人欧美在线观看| 香蕉久久夜色| 午夜福利欧美成人| 最后的刺客免费高清国语| 天堂网av新在线| 久久久久亚洲av毛片大全| 亚洲av一区综合| 老司机福利观看| 亚洲成人免费电影在线观看| 国产一区二区激情短视频| 一进一出抽搐动态| 亚洲av中文字字幕乱码综合| 欧美+亚洲+日韩+国产| 九九热线精品视视频播放| 亚洲一区高清亚洲精品| 国产探花极品一区二区| 草草在线视频免费看| bbb黄色大片| 精品久久久久久久久久免费视频| 1000部很黄的大片| 19禁男女啪啪无遮挡网站| 免费在线观看亚洲国产| 精品久久久久久久人妻蜜臀av| 97碰自拍视频| 嫩草影院精品99| 欧美3d第一页| 99久久99久久久精品蜜桃| av天堂在线播放| 18禁在线播放成人免费| 校园春色视频在线观看| 日本成人三级电影网站| 他把我摸到了高潮在线观看| 一本久久中文字幕| 国产精品野战在线观看| 国产精品久久久久久亚洲av鲁大| 亚洲性夜色夜夜综合| 18禁黄网站禁片午夜丰满| 在线国产一区二区在线| 久久国产乱子伦精品免费另类| 99久久无色码亚洲精品果冻| 丰满人妻熟妇乱又伦精品不卡| 亚洲成人久久爱视频| 特大巨黑吊av在线直播| 国产一区二区三区视频了| 黄色视频,在线免费观看| 日本三级黄在线观看| 亚洲中文字幕一区二区三区有码在线看| 中文字幕熟女人妻在线| 国产色爽女视频免费观看| 日本与韩国留学比较| 嫩草影院入口| 久久精品国产综合久久久| 精品国产三级普通话版| 1024手机看黄色片| 搞女人的毛片| 日本精品一区二区三区蜜桃| 久99久视频精品免费| 色老头精品视频在线观看| 十八禁网站免费在线| 欧美一级毛片孕妇| 99久久久亚洲精品蜜臀av| 深爱激情五月婷婷| 亚洲天堂国产精品一区在线| 神马国产精品三级电影在线观看| 欧美日韩乱码在线| 最近最新中文字幕大全电影3| 亚洲真实伦在线观看| 国产精品 国内视频| 美女被艹到高潮喷水动态| 97人妻精品一区二区三区麻豆| 男插女下体视频免费在线播放| 国产精品电影一区二区三区| 搡老岳熟女国产| 免费人成视频x8x8入口观看| 美女被艹到高潮喷水动态| 99久久精品热视频| 麻豆成人午夜福利视频| 久久精品亚洲精品国产色婷小说| 丰满人妻一区二区三区视频av | 淫妇啪啪啪对白视频| 国产真人三级小视频在线观看| bbb黄色大片| 国产乱人伦免费视频| 亚洲av成人av| 成人鲁丝片一二三区免费| 在线天堂最新版资源| 国内毛片毛片毛片毛片毛片| 丰满人妻熟妇乱又伦精品不卡| ponron亚洲| 18美女黄网站色大片免费观看| 国产探花在线观看一区二区| 男女午夜视频在线观看| 禁无遮挡网站| 特级一级黄色大片| 久久久久久久久久黄片| 性欧美人与动物交配| 国产高清视频在线播放一区| 欧美成人a在线观看| 香蕉久久夜色| 国产国拍精品亚洲av在线观看 | 国产亚洲精品一区二区www| 亚洲精品一区av在线观看| 18禁裸乳无遮挡免费网站照片| 欧美+日韩+精品| 国产成年人精品一区二区| 在线观看日韩欧美| 亚洲国产欧美网| 亚洲熟妇熟女久久| 丰满人妻熟妇乱又伦精品不卡| 亚洲精品成人久久久久久| 美女高潮的动态| 国产精品影院久久| 久久久久国内视频| 又黄又爽又免费观看的视频| 日本免费a在线| 亚洲一区二区三区不卡视频| 免费大片18禁| 欧美黑人巨大hd| 天天添夜夜摸| 欧美大码av| 在线观看一区二区三区| 麻豆国产av国片精品| 国产精品一区二区三区四区免费观看 | 在线看三级毛片| 久久香蕉精品热| 亚洲欧美一区二区三区黑人| 日韩大尺度精品在线看网址| 亚洲国产精品sss在线观看| 日韩有码中文字幕| 亚洲av二区三区四区| 最近视频中文字幕2019在线8| 国产高清三级在线| 在线观看一区二区三区| 国产69精品久久久久777片| 在线观看免费视频日本深夜| 亚洲精品国产精品久久久不卡| 中文字幕人妻熟人妻熟丝袜美 | 男插女下体视频免费在线播放| 又黄又粗又硬又大视频| 日本 av在线| 一级黄片播放器| 在线观看免费视频日本深夜| 久久久久久大精品| 黑人欧美特级aaaaaa片| 一a级毛片在线观看| 热99re8久久精品国产| 无限看片的www在线观看| 久久久久久国产a免费观看| 亚洲天堂国产精品一区在线| 3wmmmm亚洲av在线观看| 少妇的丰满在线观看| 婷婷精品国产亚洲av| 国产亚洲欧美在线一区二区| 国产又黄又爽又无遮挡在线| 成人av一区二区三区在线看| 欧美黑人巨大hd| 婷婷亚洲欧美| 国产一区二区三区在线臀色熟女| 国产97色在线日韩免费| 国产午夜福利久久久久久| 亚洲,欧美精品.| 久9热在线精品视频| 国产精品久久久久久久电影 | 真人做人爱边吃奶动态| 久久精品国产亚洲av香蕉五月| 欧美3d第一页| 国产99白浆流出| 国产精品98久久久久久宅男小说| 欧美黄色片欧美黄色片| 亚洲成a人片在线一区二区| 国产精品亚洲一级av第二区| 午夜亚洲福利在线播放| 国产欧美日韩精品一区二区| 午夜免费成人在线视频| 毛片女人毛片| 欧美不卡视频在线免费观看| 淫秽高清视频在线观看| 久久人妻av系列| 精品人妻1区二区| 久久久色成人| 婷婷亚洲欧美| 国产伦人伦偷精品视频| 人人妻人人看人人澡| 丰满人妻一区二区三区视频av | 亚洲av电影不卡..在线观看| 日韩精品青青久久久久久| 亚洲欧美日韩高清专用| 一区二区三区激情视频| 午夜福利在线观看吧| 国产黄片美女视频| 女人十人毛片免费观看3o分钟| 香蕉久久夜色| 精品久久久久久久毛片微露脸| 高潮久久久久久久久久久不卡| 日韩欧美一区二区三区在线观看| 蜜桃久久精品国产亚洲av| 成人三级黄色视频| 婷婷丁香在线五月| 欧美在线黄色| 成熟少妇高潮喷水视频| 国产一区在线观看成人免费| 一级黄片播放器| 免费看a级黄色片| 18禁黄网站禁片午夜丰满| 不卡一级毛片| 18禁裸乳无遮挡免费网站照片| 又紧又爽又黄一区二区| 69av精品久久久久久| 国产午夜精品论理片| 美女黄网站色视频| 国产aⅴ精品一区二区三区波| 免费电影在线观看免费观看| 婷婷丁香在线五月| 久久欧美精品欧美久久欧美| 真人一进一出gif抽搐免费| 欧美三级亚洲精品| 18美女黄网站色大片免费观看| 网址你懂的国产日韩在线| 欧美zozozo另类| 色老头精品视频在线观看| 91久久精品国产一区二区成人 | 午夜影院日韩av| 国产视频内射| 午夜福利欧美成人| 国产97色在线日韩免费| 波多野结衣高清无吗| 中文字幕精品亚洲无线码一区| 国产一区二区三区视频了| 午夜老司机福利剧场| 脱女人内裤的视频| 2021天堂中文幕一二区在线观| 免费在线观看亚洲国产| 欧美激情久久久久久爽电影| 国产成人福利小说| 美女被艹到高潮喷水动态| 露出奶头的视频| 桃色一区二区三区在线观看| 午夜影院日韩av| 99久久综合精品五月天人人| 91av网一区二区| 欧洲精品卡2卡3卡4卡5卡区| 美女免费视频网站| 内地一区二区视频在线| 国产精品免费一区二区三区在线| 国产精品电影一区二区三区| 久久久精品欧美日韩精品| 国产精品乱码一区二三区的特点| 成人午夜高清在线视频| 91九色精品人成在线观看| 制服丝袜大香蕉在线| 国产毛片a区久久久久| 国产精品久久视频播放| 亚洲精品在线美女| 成人性生交大片免费视频hd| 欧美+亚洲+日韩+国产| 又爽又黄无遮挡网站| 99久久精品热视频| 国产色婷婷99| 亚洲内射少妇av| 窝窝影院91人妻| 九色成人免费人妻av| 99热精品在线国产| 他把我摸到了高潮在线观看| 亚洲avbb在线观看| 91av网一区二区| 老司机福利观看| 午夜福利欧美成人| 老司机福利观看| 精华霜和精华液先用哪个| 国产精品久久久久久久久免 | 日本撒尿小便嘘嘘汇集6| 欧美日韩综合久久久久久 | 美女高潮的动态| 久久精品夜夜夜夜夜久久蜜豆| 日韩欧美国产在线观看| 美女高潮喷水抽搐中文字幕| 可以在线观看毛片的网站| 在线观看美女被高潮喷水网站 | 制服人妻中文乱码| 亚洲精品粉嫩美女一区| 国产熟女xx| 观看美女的网站| 又紧又爽又黄一区二区| 国产淫片久久久久久久久 |