It is challenging to find a conventional nanofabrication technique that can consistently produce soft polymeric matter of high surface area and nanoscale morphology in a way that is scalable, versatile, and easily tunable. Here, the capabilities of a universal method for fabricating diverse nano‐ and micro‐scale morphologies based on polymer precipitation templated by the fluid streamlines in multiphasic flow are explored. It is shown that while the procedure is operationally simple, various combinations of its intertwined mechanisms can controllably and reproducibly lead to the formation of an extraordinary wide range of colloidal morphologies. By systematically investigating the process conditions, 12 distinct classes of polymer micro‐ and nano‐structures including particles, rods, ribbons, nanosheets, and soft dendritic colloids (dendricolloids) are identified. The outcomes are interpreted by delineating the physical processes into three stages: hydrodynamic shear, capillary and mechanical breakup, and polymer precipitation rate. The insights into the underlying fundamental mechanisms provide guidance toward developing a versatile and scalable nanofabrication platform. It is verified that the liquid shear‐based technique is versatile and works well with many chemically diverse polymers and biopolymers, showing potential as a universal tool for simple and scalable nanofabrication of many morphologically distinct soft matter classes.
Self‐folding broadly refers to the assembly of 3D structures by bending, curving, and folding without the need for manual or mechanized intervention. Self‐folding is scientifically interesting because self‐folded structures, from plant leaves to gut villi to cerebral gyri, abound in nature. From an engineering perspective, self‐folding of sub‐millimeter‐sized structures addresses major hurdles in nano‐ and micro‐manufacturing. This review focuses on self‐folding using surface tension or capillary forces derived from the minimization of liquid interfacial area. Due to favorable downscaling with length, at small scales capillary forces become extremely large relative to forces that scale with volume, such as gravity or inertia, and to forces that scale with area, such as elasticity. The major demonstrated classes of capillary force assisted self‐folding are discussed. These classes include the use of rigid or soft and micro‐ or nano‐patterned precursors that are assembled using a variety of liquids such as water, molten polymers, and liquid metals. The authors outline the underlying physics and highlight important design considerations that maximize rigidity, strength, and yield of the assembled structures. They also discuss applications of capillary self‐folding structures in engineering and medicine. Finally, the authors conclude by summarizing standing challenges and describing future trends.
more » « less- NSF-PAR ID:
- 10457896
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- Volume:
- 7
- Issue:
- 5
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Conventional assembly of biosystems has relied on bottom‐up techniques, such as directed aggregation, or top‐down techniques, such as layer‐by‐layer integration, using advanced lithographic and additive manufacturing processes. However, these methods often fail to mimic the complex three dimensional (3D) microstructure of naturally occurring biomachinery, cells, and organisms regarding assembly throughput, precision, material heterogeneity, and resolution. Pop‐up, buckling, and self‐folding methods, reminiscent of paper origami, allow the high‐throughput assembly of static or reconfigurable biosystems of relevance to biosensors, biomicrofluidics, cell and tissue engineering, drug delivery, and minimally invasive surgery. The universal principle in these assembly methods is the engineering of intrinsic or extrinsic forces to cause local or global shape changes via bending, curving, or folding resulting in the final 3D structure. The forces can result from stresses that are engineered either during or applied externally after synthesis or fabrication. The methods facilitate the high‐throughput assembly of biosystems in simultaneously micro or nanopatterned and layered geometries that can be challenging if not impossible to assemble by alternate methods. The authors classify methods based on length scale and biologically relevant applications; examples of significant advances and future challenges are highlighted.
-
As miniaturization of electrical and mechanical components used in modern technology progresses, there is an increasing need for high-throughput and low-cost micro-scale assembly techniques. Many current micro-assembly methods are serial in nature, resulting in unfeasibly low throughput. Additionally, the need for increasingly smaller tools to pick and place individual microparts makes these methods cost prohibitive. Alternatively, parallel self-assembly or directed-assembly techniques can be employed by utilizing forces dominant at the micro and nano scales such as electro-kinetic, thermal, and capillary forces. However, these forces are governed by complex equations and often act on microparts simultaneously and competitively, making modeling and simulation difficult. The research in this paper presents a novel phenomenological approach to directed micro-assembly through the use of artificial intelligence to correlate micro-particle movement via dielectrophoretic and electro-osmotic forces in response to varying frequency of an applied non-uniform electric field. This research serves as a proof of concept of the application of artificial intelligence to create high yield low-cost micro-assembly techniques, which will prove useful in a variety of fields including micro-electrical-mechanical systems (MEMS), biotechnology, and tissue engineering.more » « less
-
more » « less
Abstract Transfection is an essential step in genetic engineering and cell therapies. While a number of non‐viral micro‐ and nano‐technologies have been developed to deliver DNA plasmids into the cell cytoplasm, one of the most challenging and least efficient steps is DNA transport to and expression in the nucleus. Here, the magnetic nano‐electro‐injection (MagNEI) platform is described which makes use of oscillatory mechanical stimulation after cytoplasmic delivery with high aspect‐ratio nano‐structures to achieve stable (>2 weeks) net transfection efficiency (efficiency × viability) of 50% in primary human T cells. This is, to the best of the authors’ knowledge, the highest net efficiency reported for primary T cells using a centrifuge‐free, non‐viral transfection method, in the absence of cell selection, and with a clinically relevant cargo size (>12 kbp). Wireless mechanical stimulation downregulates the expression of microtubule motor protein gene,
KIF2A , which increases local DNA concentration near the nuclei, resulting in enhanced DNA transfection. Magnetic forces also accelerate membrane repair by promoting actin cytoskeletal remodeling which preserves key biological attributes including cell proliferation and gene expressions. These results demonstrate MagNEI as a powerful non‐viral transfection technique for progress toward fully closed, end‐to‐end T cell manufacturing with less human labor, lower production cost, and shorter delay. -
Objects that deform a liquid interface are subject to capillary forces, which can be harnessed to assemble the objects1–4. Once assembled, such structures are generally static. Here we dynamically modulate these forces to move objects in programmable two-dimensional patterns. We 3D-print devices containing channels that trap floating objects using repulsive capillary forces5,6, then move these devices vertically in a water bath. Because the channel cross-sections vary with height, the trapped objects can be steered in two dimensions. The device and interface therefore constitute a simple machine that converts vertical to lateral motion. We design machines that translate, rotate and separate multiple floating objects and that do work on submerged objects through cyclic vertical motion. We combine these elementary machines to make centimetre-scale compound machines that braid micrometre-scale filaments into prescribed topologies, including non-repeating braids. Capillary machines are distinct from mechanical, optical or fluidic micromanipulators in that a meniscus links the object to the machine. Therefore, the channel shapes need only be controlled on the scale of the capillary length (a few millimetres), even when the objects are microscopic. Consequently, such machines can be built quickly and inexpensively. This approach could be used to manipulate micrometre-scale particles or to braid microwires for high-frequency electronics.more » « less
