The Fluid Joint: The Soft Spot of Micro‐ and Nanosystems

Abstract

Fluid bridges are ubiquitous soft structures of finite size that conform to and link the surfaces of neighboring objects. Fluid joints, the specific type of fluid bridge with at least one extremity constrained laterally, display even more pronounced reactivity and self-restoration, which make them remarkably suited for assembly, actuation, and manipulation purposes. Their peculiar surface and bulk properties place fluid joints at the rich intersection of diverse scientific interests, and foster their widespread use throughout micro- and nanotechnology. A critical survey of the mechanics and of the manifold applications of fluid bridges and joints in micro- and nanosystems is presented here, along with current challenges and multidisciplinary perspectives.

Manipulation of Colloidal Particles in Three Dimensions via Microfluid Engineering

“…[34,35] However, the controllable construction of 3D architectures, which has more complex spatial arrangements of nanoparticles than 2D ones, remains challenging because www.advmat.de www.advancedsciencenews.com sandwich-shaped patterning system, which includes the desired flat substrate, aqueous solution with building blocks, and a template with periodically arranged micropillars, is applied in this study. [53] 3D architectures with controllable cross-sections and shapes are obtained by tuning the template with various pinning point numbers (which control the architecture shape) and physical parameters of the system (which control the architecture cross-section). This new strategy can introduce several advantages for the 3D architecture construction: (i) regulation of nucleation locationthe pinned microfluid has a lower evaporation rate than the unpinned part; therefore, there is a directed flow toward the corner of the microfluid; [52] (ii) steady growth rate, where the assembly velocity of nanoparticles mainly depends on the str ength of the directed flow, which remains constant because of the pinning effect; [47] (iii) controlled growth orientation, where the regulated morphology of the microfluid arranges the growth orientation of the architecture along the arc of microfluid.…”

Self-assembly of micro/nanosystems across scales and interfaces

“…Particularly, liquid-induced stiction, earlier responsible for low yields in the release of surface-machined microelectromechanical systems (MEMS), has more recently been turned into a passive and precise manipulation technique for (sub-)millimetric components [4,12]. The capillary action of confined liquid bridges [15] is here exploited to bring components in accurate registration with binding sites patterned on a target substrate or on another component (Fig. 2).…”

“…Once assembled, the component stands on a fluid joint that reacts elastically to small perturbations along all its six degrees of freedom [15]. Small, uniaxial lateral displacements of components have been mostly characterized and modeled [12], given their relevance for precision microelectronic packaging.…”

“…SA offered massively parallel and scalable assembly methods that could complement, extend and eventually replace pick-and-place approaches [12]; it provided means of self-actuation to deploy three-dimensional micro-electrooptical systems and self-fold polyhedral particles and origami-based structures [5,13]; and it enabled contactless handling [4], predictable crystallization [14] and precise placement [15] of very large quantities of micro-and nanocomponents. Arguably, among the many implementations proposed in the last two decades, and surveyed in recent comprehensive reviews [3-5, 16, 17], the aforementioned stand also as the applications of SA to the fabrication of technological devices that so far have best delivered to their promises, to the point of raising industrial interests.…”

Continuous and discontinuous transitions between two types of capillary bridges on a beaded chain pulled out from a liquid

“…Capillary bridges play important role in many physical phenomena, including agglomeration, 1-3 mechanical strengthening, [4][5][6] surface adhering, 7,8 rheological response, [9][10][11] capillarygripping 12,13 and self-assembly. [14][15][16] They are often utilized in material science, e.g. for fabricating new materials using capillary suspensions, [17][18][19] new structures, [20][21][22] in nanolithography, [23][24][25] microplating, 26 for pattern formation, 27 and in printed electronics technologies.…”