Ganan-V1,3 9

fashion? Following the findings of nature itself, for which the liquid phase has been the essential ground for the emergence of chemical complexity and life, we focus on those processes involving manipulation of liquid phase on the microscale and, in particular, those offering homogen eous and repr oducible yield . The last two decades have witnessed an explosive expansion in the under- standing of capillary processes; this knowledge has served human creativity and the development of a number of technologies now considered forming a part icula r field of fluid mech anic s: micr ofluid ics. In this field , the intel lige nt combination of imposed geometries (devices) on small scales, surface tension and bulk forces tuned at precise intensities provides the tools to manipu- late matter in an unprecedent wa y . Here, dropl ets, bubbles, microcapsul es, micr ofibers, etc. become basic building block s of new func tional mate rials, intelligent ingredien ts and APIs. While mass producti vity pertains functional product manufacturing enough for current human demands, control of the microscopic scale directly influences product delivery to an individual organism. This review aims to provide a gross mapping of current scientific and technological knowledge in the field, in the quest for those current tools combining highest productivity with maximal control on the microscale and reproducibility. APIs can be present in many forms: solid dispersions (powders made up of solid particles), suspensions (powders in liquids) of any kind, emulsions (droplets of any size in immiscible liquids), solutions (API’s molecules dis- persed in a solvent), etc. Nearly alwa ys, a fragmentation process is involv ed in these forms. The most controllable way to fragment a bulk material involves its reductio n to liqu id phase (melting or dissolution), fragmen ting the liqui d phase into droplets by the use of specific tools, and applying a further step to solidify it (fre ezin g or desolvation), if necessar y . In gene ral, a high degree of care put into the liquid fragmentation step demands a careful subsequent solidifying step as well, to prevent undesired coalescence . Interestingly, some researchers have successfully proposed the use of electric charges to prevent such coale scence [38]. How ev er, fragmen tation inv olv es manip ulati on tools adapted to the inherent nature of this process: first, it always stores energy in the form of surface tension, and second, this storage should be as ordered as compatible with the functionality and control sought for, thus minimiz- ing entrop y . These dema nds go against Thermodynamics in many aspect s. Therefore, the inventive steps involved in the design of liquid fragmentation tools are much taller than those demanded in subsequent solidifying steps. 9

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7/27/2019 Ganan-V1,3 9

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fashion? Following the findings of nature itself, for which the liquid phase hasbeen the essential ground for the emergence of chemical complexity and life,we focus on those processes involving manipulation of liquid phase on themicroscale and, in particular, those offering homogeneous and reproducible

yield .

The last two decades have witnessed an explosive expansion in the under-standing of capillary processes; this knowledge has served human creativityand the development of a number of technologies now considered forming aparticular field of fluid mechanics: microfluidics. In this field, the intelligentcombination of imposed geometries (devices) on small scales, surface tensionand bulk forces tuned at precise intensities provides the tools to manipu-late matter in an unprecedent way. Here, droplets, bubbles, microcapsules,microfibers, etc. become basic building blocks of new functional materials,intelligent ingredients and APIs. While mass productivity pertains func-tional product manufacturing enough for current human demands, control

of the microscopic scale directly influences product delivery to an individualorganism. This review aims to provide a gross mapping of current scientificand technological knowledge in the field, in the quest for those current toolscombining highest productivity with maximal control on the microscale andreproducibility.

APIs can be present in many forms: solid dispersions (powders made upof solid particles), suspensions (powders in liquids) of any kind, emulsions(droplets of any size in immiscible liquids), solutions (API’s molecules dis-persed in a solvent), etc. Nearly always, a fragmentation process is involved inthese forms. The most controllable way to fragment a bulk material involvesits reduction to liquid phase (melting or dissolution), fragmenting the liquid

phase into droplets by the use of specific tools, and applying a further stepto solidify it (freezing or desolvation), if necessary. In general, a high degreeof care put into the liquid fragmentation step demands a careful subsequentsolidifying step as well, to prevent undesired coalescence . Interestingly, someresearchers have successfully proposed the use of electric charges to preventsuch coalescence [38]. However, fragmentation involves manipulation toolsadapted to the inherent nature of this process: first, it always stores energy

in the form of surface tension, and second, this storage should be as ordered

as compatible with the functionality and control sought for, thus minimiz-ing entropy. These demands go against Thermodynamics in many aspects.Therefore, the inventive steps involved in the design of liquid fragmentationtools are much taller than those demanded in subsequent solidifying steps.