Assembly Of 3D Structures Research Articles

Simplified geometric representations of protein structures identify complementary interaction interfaces.

Protein‐protein interactions are critical to protein function, but three‐dimensional (3D) arrangements of interacting proteins have proven hard to predict, even given the identities and 3D structures of the interacting partners. Specifically, identifying the relevant pairwise interaction surfaces remains difficult, often relying on shape complementarity with molecular docking while accounting for molecular motions to optimize rigid 3D translations and rotations. However, such approaches can be computationally expensive, and faster, less accurate approximations may prove useful for large‐scale prediction and assembly of 3D structures of multi‐protein complexes. We asked if a reduced representation of protein geometry retains enough information about molecular properties to predict pairwise protein interaction interfaces that are tolerant of limited structural rearrangements. Here, we describe a reduced representation of 3D protein accessible surfaces on which molecular properties such as charge, hydrophobicity, and evolutionary rate can be easily mapped, implemented in the MorphProt package. Pairs of surfaces are compared to rapidly assess partner‐specific potential surface complementarity. On two available benchmarks of 185 overall known protein complexes, we observe predictions comparable to other structure‐based tools at correctly identifying protein interaction surfaces. Furthermore, we examined the effect of molecular motion through normal mode simulation on a benchmark receptor‐ligand pair and observed no marked loss of predictive accuracy for distortions of up to 6 Å Cα‐RMSD. Thus, a shape reduction of protein surfaces retains considerable information about surface complementarity, offers enhanced speed of comparison relative to more complex geometric representations, and exhibits tolerance to conformational changes.

Self‐Folding Using Capillary Forces

AbstractSelf‐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.

Pop-up assembly of 3D structures actuated by heat shrinkable polymers

Folding 2D sheets into desired 3D structures is a promising fabrication technique that can find a wide range of applications. Compressive buckling provides an attractive strategy to actuate the folding and can be applied to a broad range of materials. Here a new and simple method is reported to achieve controlled compressive buckling, which is actuated by a heat shrinkable polymer sheet. The buckling deformation is localized at the pre-defined creases in the 2D sheet, resulting in sharp folding. Two approaches are developed to actuate the transformation, which follow similar geometric rules. In the first approach, the 2D precursor is pushed from outside, which leads to a 3D structure surrounded by the shrunk polymer sheet. Assembled 3D structures include prisms/pyramids with different base shapes, house roof, partial soccer ball, Miura-ori structure and insect wing. In the second approach, the 2D precursor is pulled from inside, which leads to a 3D structure enclosing the shrunk polymer sheet. Prisms/pyramids with different base shapes are assembled. The assembled structures are further tessellated to fabricate cellular structures that can be used as thermal insulator and crash energy absorber. They are also stacked vertically to fabricate complex multilayer structures.

Graphene-Based Polymer Bilayers with Superior Light-Driven Properties for Remote Construction of 3D Structures.

3D structure assembly in advanced functional materials is important for many areas of technology. Here, a new strategy exploits IR light‐driven bilayer polymeric composites for autonomic origami assembly of 3D structures. The bilayer sheet comprises a passive layer of poly(dimethylsiloxane) (PDMS) and an active layer comprising reduced graphene oxides (RGOs), thermally expanding microspheres (TEMs), and PDMS. The corresponding fabrication method is versatile and simple. Owing to the large volume expansion of the TEMs, the two layers exhibit large differences in their coefficients of thermal expansion. The RGO‐TEM‐PDMS/PDMS bilayers can deflect toward the PDMS side upon IR irradiation via the cooperative effect of the photothermal effect of the RGOs and the expansion of the TEMs, and exhibit excellent light‐driven, a large bending deformation, and rapid responsive properties. The proposed RGO‐TEM‐PDMS/PDMS composites with excellent light‐driven bending properties are demonstrated as active hinges for building 3D geometries such as bidirectionally folded columns, boxes, pyramids, and cars. The folding angle (ranging from 0° to 180°) is well‐controlled by tuning the active hinge length. Furthermore, the folded 3D architectures can permanently preserve the deformed shape without energy supply. The presented approach has potential in biomedical devices, aerospace applications, microfluidic devices, and 4D printing.

Controlled mechanical buckling for origami-inspired construction of 3D microstructures in advanced materials.

Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches of origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies and/or capability of control over the transformation. Here, we introduce an approach that exploits controlled mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as an effective strategy to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system-level examples of soccer balls, model houses, cars, and multi-floor textured buildings.

3D‐Branched ZnO/CdS Nanowire Arrays for Solar Water Splitting and the Service Safety Research

Modulation of broadband light trapping through assembly of 3D structures and modification with narrow band‐gap semiconductors provide an effective way to improve the photoelectrochemical (PEC) performance. Here, 3D‐branched ZnO nanowire arrays (NWAs) modified with cadmium sulfide (CdS) nanoparticles are designed and synthesized via solution chemical routes. The 3D‐branched ZnO NWA–CdS nanoparticle photoanodes show an excellent PEC performance in UV and visible region and the maximum photo‐to‐hydrogen conversion efficiency reaches to 3.1%. The high performance of 3D‐branched ZnO NWA–CdS composites is mainly attributed to the excellent carrier collection capability and high light‐trapping ability of 3D‐branched ZnO NWAs as well as the excellent photocatalytic activity of CdS nanoparticles in the visible region. In addition, the photocorrosion mechanism of 3D‐branched ZnO NWA–CdS photoanodes is systematically investigated, and a protective TiO2 layer is deposited onto the photoanodes to elevate the PEC stability. The results benefit a deeper understanding of the role of 3D‐branched structures decorated with narrow band‐gap semiconductors in solar water splitting.

Microfluidic direct writer with integrated declogging mechanism for fabricating cell-laden hydrogel constructs

Cell distribution and nutrient supply in 3D cell-laden hydrogel scaffolds are critical and should mimic the in vivo cellular environment, but been difficult to control with conventional fabrication methods. Here, we present a microfluidic direct writer (MFDW) to construct 3D cell-laden hydrogel structures with openings permitting media exchange. The MFDW comprises a monolithic microfluidic head, which delivers coaxial streams of cell-laden sodium alginate and calcium chloride solutions to form hydrogel fibers. Fiber diameter is controlled by adjusting the ratio of the volumetric flow rates. The MFDW head is mounted on a motorized stage, which is automatically controlled and moves at a speed synchronized with the speed of fiber fabrication. Head geometry, flow rates, and viscosity of the writing solutions were optimized to prevent the occurrence of curling and bulging. For continuous use, a highly reliable process is needed, which was accomplished with the integration of a declogging conduit supplying a solvent to dissolve the clogging gel. The MFDW was used for layer-by-layer fabrication of simple 3D structures with encapsulated cells. Assembly of 3D structures with distinct fibers is demonstrated by alternatively delivering two different alginate gel solutions. The MFDW head can be built rapidly and easily, and will allow 3D constructs for tissue engineering to be fabricated with multiple hydrogels and cell types.

Simultaneous microscale optical manipulation, fabrication and immobilisation in aqueous media

Efficient multiphoton radical generation chemistry has been developed for use in aqueous media. Through a combination of multiphoton absorption polymerisation (MAP) and optical tweezers, this chemistry has been applied to the fabrication, manipulation, and assembly of 3D polymeric and biomolecular structures. Combining MAP and optical tweezers allows for the direct assembly of 3D structures from microscale objects as well as for the realisation of structures, such as tape-like and rope-like microthreads, that can be used for unconventional microfabrication techniques including microbraiding and microweaving. These capabilities significantly expand the toolbox of methods available for the creation of functional microstructures in aqueous media.

BioMEMS Technologies for Regenerative Medicine

AbstractThe emergence of BioMEMS fabrication technologies such as soft lithography, micromolding and assembly of 3D structures, and biodegradable microfluidics, are already making significant contributions to the field of regenerative medicine. Over the past decade, BioMEMS have evolved from early silicon laboratory devices to polymer-based structures and even biodegradable constructs suitable for a range ofex vivoandin vivoapplications. These systems are still in the early stages of development, but the long-term potential of the technology promises to enable breakthroughs in health care challenges ranging from the systemic toxicity of drugs to the organ shortage.Ex vivosystems for organ assist applications are emerging for the liver, kidney and lung, and the precision and scalability of BioMEMS fabrication techniques offer the promise of dramatic improvements in device performance and patient outcomes.Ultimately, the greatest benefit from BioMEMS technologies will be realized in applications for implantable devices and systems. Principal advantages include the extreme levels of achievable miniaturization, integration of multiple functions such as delivery, sensing and closed loop control, and the ability of precision microscale and nanoscale features to reproduce the cellular microenvironment to sustain long-term functionality of engineered tissues. Drug delivery systems based on BioMEMS technologies are enabling local, programmable control over drug concentrations and pharmacokinetics for a broad spectrum of conditions and target organs. BioMEMS fabrication methods are also being applied to the development of engineered tissues for applications such as wound healing, microvascular networks and bioartificial organs. Here we review recent progress in BioMEMS-based drug delivery systems, engineered tissue constructs and organ assist devices for a range ofex vivoandin vivoapplications in regenerative medicine.

Synthesis and patterning of nanostructures of (almost) anything on anything

A necessary and very challenging condition for progress in nanoscience is being able to synthesize the requisite material. While there has been substantial success for some materials, one would like to develop protocols to fabricate structures of a wide variety of materials on an equally wide range of supports, preferably with size selection and the ability to pattern on large areas at low cost. The paper by Kerner and Asscher in this issue [1] is significant because it shows how at least some of those conditions can be satisfied in a novel and creative way. Building on the techniques of surface science, many researchers have focused on physical vapor deposition and the subsequent assembly of 1D wires, 2D islands, and 3D clusters. The problem, of course, is that Nature provides rather stringent rules that prevent the spontaneous assembly of 3D structures for all but a few materials. In particular, 3D growth will occur only if the adatoms interact only weakly with the surface but strongly with one another, with details dictated by surface and interface energies. A technique was developed a few years ago that by-passed these rules, termed buffer-layer-assistedgrowth (BLAG) [2–4], and the paper by Kerner and Asscher combines this technique with laser induced thermal desorption to form patterns in a novel and potentially important way. The idea behind buffer layer assisted growth is remarkably simple, as depicted in Fig. 1. The buffer layer replaces adatom–substrate interactions with very weak adatom–buffer interactions so that balling-up occurs out of contact with the substrate. The buffer must subsequently be removed so that the clusters are delivered in the ultimate of soft landings to the substrate where wetting is frustrated by kinetics. While there