Donina Liva, Rafique Aysha, Khodaparast Sepideh, Porcar Lionel, Cabral João T
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
Institut Laue-Langevin, 71 Avenue des Martyrs, B.P. 156, F-38042 Grenoble CEDEX, France.
Soft Matter. 2021 Nov 17;17(44):10053-10062. doi: 10.1039/d1sm01215k.
The lamellar-to-multilamellar vesicle (MLV) transformation in a model surfactant system, sodium dodecyl sulfate (SDS), octanol and brine, is investigated under continuous and oscillatory microfluidic contraction-expansion flows, employing polarised optical microscopy and small angle neutron scattering (SANS), with sample volume probed down to ≃20 nL. We determine the lamellar-to-MLV transition requirements at varying flow velocity, oscillation amplitude, frequency, and number of oscillatory cycles. The spatio-temporal evolution of the hierarchical fluid structure is elucidated: lamellar sheets initially align with flow direction upon entering a constriction and then perpendicularly upon exiting; the formation of MLVs at the nanoscale is first observed by SANS within a few (<5) oscillatory cycles, followed by the gradual appearance of a regular (albeit not crystalline) MLV arrangement, at the micronscale, by optical microscopy after tens of cycles, under the conditions investigated. Once MLVs form under flow, these remain metastable for several days.
在连续和振荡微流体收缩-膨胀流条件下，利用偏振光学显微镜和小角中子散射（SANS），对一种模型表面活性剂体系（十二烷基硫酸钠（SDS）、辛醇和盐水）中从层状囊泡到多层囊泡（MLV）的转变进行了研究，所探测的样品体积低至约20 nL。我们确定了在不同流速、振荡幅度、频率和振荡周期数下从层状囊泡到MLV转变的条件。阐明了分级流体结构的时空演变：层状薄片在进入收缩区时最初与流动方向对齐，然后在离开时垂直对齐；在研究的条件下，通过SANS在几个（<5）振荡周期内首次在纳米尺度上观察到MLV的形成，随后在数十个周期后通过光学显微镜在微米尺度上逐渐出现规则（尽管不是结晶的）MLV排列。一旦MLV在流动条件下形成，它们会在几天内保持亚稳态。
