Differentially photo-crosslinked polymers enable self-assembling microfluidics

Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Nature Communications (Impact Factor: 11.47). 11/2011; 2(1):527. DOI: 10.1038/ncomms1531
Source: PubMed


An important feature of naturally self-assembled systems such as leaves and tissues is that they are curved and have embedded fluidic channels that enable the transport of nutrients to, or removal of waste from, specific three-dimensional regions. Here we report the self-assembly of photopatterned polymers, and consequently microfluidic devices, into curved geometries. We discover that differentially photo-crosslinked SU-8 films spontaneously and reversibly curve on film de-solvation and re-solvation. Photolithographic patterning of the SU-8 films enables the self-assembly of cylinders, cubes and bidirectionally folded sheets. We integrate polydimethylsiloxane microfluidic channels with these SU-8 films to self-assemble curved microfluidic networks.

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    • "Fabrication of well-ordered soft-matter-based micro and nano structures over large area has drawn great interests in recent years due to their increasing applicability in polymer electronics1, soft machines2, flash memory, chemical and biosensors345, particularly biological applications such as tissue-engineering6, surface modification78 and microfluidics9. Owing to the importance associated with the soft-matter-based micro and nano structures, numerous conventional experimental methods have been developed to date to fabricate the pattern of functional soft-matters, such as photolithography10, inkjet printing11, direct-laser writing12, dip-pen and polymer pen lithography131415. Although these techniques are mature for use in microelectronics and contributed important roles in modern digital life for the high density of integration, less power consumption and good performances, they do have some limitations, such as high operational costs from the high-priced equipment and clean room demanding processes, incompatibility with curved surfaces, poor suitability for three-dimensional (3D) fabrication, little or no control over surface chemistry and exclusive application in the direct patterning of a limited set of functional materials16. "
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    ABSTRACT: Patterning of functional soft matters at different length scales is important for diverse research fields including cell biology, tissue engineering and medicinal science and the development of optics and electronics. Here we have further improved a simple but very efficient method, selective contact thermochemical reaction (SCTR), for patterning soft matters over large area with a sub-100 nm resolution. By selecting contact between different precursors through a topographically patterned PDMS stamp and subsequently any heating way for thermalchemical reaction, thermal-related soft matters can be patterned to form controllable micro or nano structures, even three-dimensional structures. The fine tunability and controllability of as-prepared micro and nano structures demonstrate this versatile approach a far wide range of uses than the merely academic.
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    ABSTRACT: Self-folding broadly refers to self-assembly processes wherein thin films or interconnected planar templates curve, roll-up or fold into three dimensional (3D) structures such as cylindrical tubes, spirals, corrugated sheets or polyhedra. The process has been demonstrated with metallic, semiconducting and polymeric films and has been used to curve tubes with diameters as small as 2nm and fold polyhedra as small as 100nm, with a surface patterning resolution of 15nm. Self-folding methods are important for drug delivery applications since they provide a means to realize 3D, biocompatible, all-polymeric containers with well-tailored composition, size, shape, wall thickness, porosity, surface patterns and chemistry. Self-folding is also a highly parallel process, and it is possible to encapsulate or self-load therapeutic cargo during assembly. A variety of therapeutic cargos such as small molecules, peptides, proteins, bacteria, fungi and mammalian cells have been encapsulated in self-folded polymeric containers. In this review, we focus on self-folding of all-polymeric containers. We discuss the mechanistic aspects of self-folding of polymeric containers driven by differential stresses or surface tension forces, the applications of self-folding polymers in drug delivery and we outline future challenges.
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    ABSTRACT: We investigated the folding of rectangular stimuli-responsive hydrogel-based polymer bilayers with different aspect ratios and relative thicknesses placed on a substrate. It was found that long-side rolling dominates at high aspect ratios (ratio of length to width) when the width is comparable to the circumference of the formed tubes, which corresponds to a small actuation strain. Rolling from all sides occurs for higher actuation, namely when the width and length considerably exceed the deformed circumference. In the case of moderate actuation, when both the width and length are comparable to the deformed circumference, diagonal rolling is observed. Short-side rolling was observed very rarely and in combination with diagonal rolling. On the basis of experimental observations, finite-element modeling and energetic considerations, we argued that bilayers placed on a substrate start to roll from corners due to quicker diffusion of water. Rolling from the long-side starts later but dominates at high aspect ratios, in agreement with energetic considerations. We have shown experimentally and by modeling that the main reasons causing a variety of rolling scenarios are (i) non-homogenous swelling due to the presence of the substrate and (ii) adhesion of the polymer to the substrate.
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