A facile one-step fabrication of large-area multicolored emissive photopatterns in mixed quantum dot-polymer films is demonstrated. This is in sharp contrast to the current photopatterning approaches that utilize only a single quantum dot (QD) component for single-color patterns. Strategies are presented that allow for either selective or collective modification of specific predetermined photoluminescent peaks of green and red QDs during photopattern development. These strategies yield novel patterns and allow for unprecedented control over how the color contrast of the photopattern evolves with continuous light illumination. These results clearly show that the evolution of the emission spectra of a multicolor mixed QD-polymer film can be readily tailored during pattern development, either by careful selection of the excitation wavelength or through combinations of controllably unstable and stable QDs with different recovery rates. Notably, these strategies are simple, fast, and robust, yielding high-resolution microscopic patterns over large areas (up to fractions of a cm²). Furthermore, the flexibility and capabilities of these strategies greatly expand the potential applications of multicolor emissive photopatterns, particularly in the areas of sensing, imaging, and lasing systems where it is important to exert delicate control over the intensity of selected colors within specific spatial regions.

Multicompartmental responsive microstructures with the capability for the pre-programmed sequential release of multiple target molecules of opposite solubility (hydrophobic and hydrophilic) in a controlled manner have been fabricated. Star block copolymers with dual-responsive blocks (temperature for poly(N-isopropylacrylamide) chains and pH for poly(acrylic acid) and poly(2-vinylpyridine) arms) and unimolecular micellar structures serve as nanocarriers for hydrophobic molecules in the microcapsule shell. The interior of the microcapsule can be loaded with water-soluble hydrophilic macromolecules. For these dual-loaded microcapsules, a programmable and sequential release of hydrophobic and hydrophilic molecules from the shell and core, respectively, can be triggered independently by temperature and pH variations. These stimuli affect the hydrophobicity and chain conformation of the star block copolymers to initiate out-of-shell release (elevated temperature), or change the overall star conformation and interlayer interactions to trigger increased permeability of the shell and out-of-core release (pH). Reversing stimulus order completely alters the release process.

Multicompartmental responsive microstructures with the capability for the pre-programmed sequential release of multiple target molecules of opposite solubility (hydrophobic and hydrophilic) in a controlled manner have been fabricated. Star block copolymers with dual-responsive blocks (temperature for poly(N-isopropylacrylamide) chains and pH for poly(acrylic acid) and poly(2-vinylpyridine) arms) and unimolecular micellar structures serve as nanocarriers for hydrophobic molecules in the microcapsule shell. The interior of the microcapsule can be loaded with water-soluble hydrophilic macromolecules. For these dual-loaded microcapsules, a programmable and sequential release of hydrophobic and hydrophilic molecules from the shell and core, respectively, can be triggered independently by temperature and pH variations. These stimuli affect the hydrophobicity and chain conformation of the star block copolymers to initiate out-of-shell release (elevated temperature), or change the overall star conformation and interlayer interactions to trigger increased permeability of the shell and out-of-core release (pH). Reversing stimulus order completely alters the release process.

We have demonstrated the facile formation of reversible and fast self-rolling biopolymer microstructures from sandwiched active–passive, silk-on-silk materials. Both experimental and modeling results confirmed that the shape of individual sheets effectively controls biaxial stresses within these sheets, which can self-roll into distinct 3D structures including microscopic rings, tubules, and helical tubules. This is a unique example of tailoring self-rolled 3D geometries through shape design without changing the inner morphology of active bimorph biomaterials. In contrast to traditional organic-soluble synthetic materials, we utilized a biocompatible and biodegradable biopolymer that underwent a facile aqueous layer-by-layer (LbL) assembly process for the fabrication of 2D films. The resulting films can undergo reversible pH-triggered rolling/unrolling, with a variety of 3D structures forming from biopolymer structures that have identical morphology and composition.

We have demonstrated the facile formation of reversible and fast self-rolling biopolymer microstructures from sandwiched active–passive, silk-on-silk materials. Both experimental and modeling results confirmed that the shape of individual sheets effectively controls biaxial stresses within these sheets, which can self-roll into distinct 3D structures including microscopic rings, tubules, and helical tubules. This is a unique example of tailoring self-rolled 3D geometries through shape design without changing the inner morphology of active bimorph biomaterials. In contrast to traditional organic-soluble synthetic materials, we utilized a biocompatible and biodegradable biopolymer that underwent a facile aqueous layer-by-layer (LbL) assembly process for the fabrication of 2D films. The resulting films can undergo reversible pH-triggered rolling/unrolling, with a variety of 3D structures forming from biopolymer structures that have identical morphology and composition.

Engineered metal-dielectric-metal nanostructures with broadband absorbing properties in the visible spectral range are fabricated by combining the plasmonic resonances of different noble metal nanostructures. Silver nanocubes and gold nanogratings couple to each other using a dielectric polymer spacer with controllable thickness, resulting in a large multiplicative enhancement of absorption properties across a broad spectral range. Narrow, long nanogrooves in a gold film are first fabricated using electron beam lithography, after which a polymer spacer layer with a controllable thickness ranging from 4 to 12 nm is assembled by spin-assisted layer-by-layer assembly. Finally, silver nanocubes with different surface coverages ranging from 12% to 22% are deposited using the Langmuir–Blodgett technique. The individual plasmon resonances of these different nanostructures are located at significantly different optical frequencies and are tuned in this study to allow a significant increase of light absorbance of the original gratings to an average value of 84% across the broad wavelength range of 450–850 nm.

The fabrication of ordered arrays of self-encapsulated “micro-bubble” material constructs based on the capillary-driven collapse of flexible silk fibroin sheets during propagation of the diffusion front of the encapsulated material is demonstrated. The individual micro-bubbles of different shapes are composed of a sacrificial material encapsulated within the ultrathin silk coating, which covers and seals the inner material during dissolution of supporting layer. The array of microscopic rectangular multi-layer silk sheets on supporting polymer layers can be selectively dissolved along the edges to initiate their self-encapsulation. The resulting micro-bubble morphology, shape, and arrangements can be readily pre-programmed by controlling the geometry of the silk sheets, such as thickness, dimension, and aspect ratio. These micro-bubble constructs can be utilized for encapsulation of various materials as well as nanoparticles in a single or multi compartmental manner. These biocompatible and biodegradable micro-bubble constructs present a promising platform for one-shot spatial and controllable loading and locking material arrays with addressable abilities.

Biologically inspired materials and structures with tailored biological, physical, and chemical properties provide an indispensable platform to actively modulate and protect cell function in hostile and synthetic environments (e.g., devices or matrices). Herein, recent innovations are discussed in cell surface engineering methods based on bulk hydrogels, microgels, and ultrathin capsules derived from inorganic, polymeric, biomolecular, or nanoparticle materials applicable to various protective and interaction mediating applications. These biomimetic cell coatings can dramatically increase cell viability and stability in a hostile environment and expand their applicability for demanding biomedical, biotechnology, and bioelectronics applications. Some of the most recent studies of traditional inorganic and organic gels, polymeric and biomolecular microgels, and ultrathin conformal soft shells from polymers and proteins are also discussed. Proper selection of chemical composition and assembly conditions has potential to dramatically enhance viability of encapsulated cells by increasing their mechanical stability, masking the cell surface from immunological agents, increasing mechanical stability, and providing chemical resistance to aggressive environments. Some recent examples of such robust and viable protected cells for biotechnology and bioelectronics are presented.

Highly localized light-induced phase transformation of electron beam induced deposited carbon nanostructures (dots and squares) on noble metal surfaces is reported. The phase transformation from the amorphous phase to the disordered graphitic phase is analyzed using the characteristic Raman signatures for amorphous and graphitized carbon and conductive force microscopy. The extent of the transformation is found to be largely dependent on the plasmon absorption properties of the underlying metal film. It is observed that the amorphous carbon deposits on the silver films consisting of 12 nm particles with the plasmon absorption near the laser excitation wavelength (514 nm), undergo fast graphitization to a nanocrystalline or a disordered graphitic phase. This transformation results in the formation of a highly conductive carbon/metal interface with at least seven orders of magnitude lower electrical resistivity than the initial insulating interface. It is suggested that the fast graphitization of nanoscale carbon deposits might serve as an efficient path for the formation of complex patterned nanoscale metal-carbon interconnects with high electrical conductivity.

A condensed overview discusses the existing grafting approaches and the surface behavior of various hyperbranched polymers. We focus on the recent strategies and corresponding characterization of the resulting surface morphologies and structures with a number of relevant recent results from the authors' own research and existing literature. Some results discussed here are important for prospective applications of hyperbranched polymers in biomedical fields, for resistive coatings, tough blends, and reinforced nanocomposites are briefly summarized as well. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 83–100, 2012

A novel type of all-natural, biocompatible, and very robust nanoscale free-standing biohybrids are reported. They are obtained by integrating a silk fibroin matrix with functional inorganic nanoplatelets using a spin-assisted layer-by-layer assembly. The organized assembly of the silk fibroin with clay (montmorillonite) nanosheets results in highly transparent nanoscale films with significantly enhanced mechanical properties, including strength, toughness, and elastic modulus, as compared to those for the pristine silk nanomaterials. Moreover, replacing clay nanoplatelets with a highly reflective Langmuir monolayer of densely packed silver nanoplates causes a similar enhancement of the mechanical properties, but in contrast to the materials above, highly reflective, mirror-like, nanoscale flexible films are created. This strategy offers a new perspective for the fabrication of robust all-natural flexible nanocomposites with exceptional mechanical properties important for biomedical applications, such as reinforced tissue engineering. On the other hand, the ability to convert silk-based nanoscale films into mirror-like biocompatible flexible films can be intriguing for prospective photonics and optical exploitation of these nanobiohybrids.

Here, the results of a study of the mechanism of bio-enabled surface-mediated titania nanoparticle synthesis with assistance of polyelectrolyte surfaces are reported. By applying atomic force microscopy, surface force spectroscopy, circular dichroism, and in situ attenuated total reflection Fourier-transform infrared spectroscopy, structural changes of rSilC-silaffin upon its adsorption to polyelectrolyte surfaces prior to and during titania nanoparticle growth are revealed. It is demonstrated that the adhesion of rSilC-silaffin onto polyelectrolyte surfaces results in its reorganization from a random-coil conformation in solution into a mixed secondary structure with both random coil and β-sheet structures presented. Moreover, the protein forms a continuous molecularly thin layer with well-defined monodisperse nanodomains of lateral dimensions below 20 nm. It is also shown that rSilC embedded inside the polylelectrolyte matrix preserves its titania formation activity. It is suggested that the surface-mediated, bio-enabled synthesis of nanostructured materials might be useful to develop general procedures for controlled growth of inorganic nanomaterials on reactive organic surfaces, which opens new perspectives in the design of tailored, in situ grown, hybrid inorganic–organic nanomaterials.

The transformation of periodic microporous structures fabricated by interference lithography followed by their freezing below glass transition is described. Periodic porous microstructures subjected to internal compressive stresses can undergo sudden structural transformation at a critical strain. The pattern transformation of collapsed pores is caused by the stresses originated during the polymerization of acrylic acid (rubbery component) inside of cylindrical pores and the subsequent solvent evaporation in the organized microporous structure. By confining the polymerization of acrylic acid to localized porous areas complex microscopic periodic structures can be obtained. The control over the mechanical instabilities in periodic porous solids at a sub-micron scale demonstrated here suggests the potential mechanical tunability of photonic, transport, adhesive, and phononic properties of such periodic porous solids.

Bioinspired design is an engineering approach that involves working to understand the design principles and strategies employed by biology in order to benefit the development of engineered systems. From a materials perspective, biology offers an almost limitless source of novel approaches capable of arousing innovation in every aspect of materials, including fabrication, design, and functionality. Here, recent and ongoing work on the study of bioinspired materials for sensing applications is presented. Work presented includes the study of fish flow receptor structures and the subsequent development of similar structures to improve flow sensor performance. The study of spider air-flow receptors and the development of a spider-inspired flexible hair is also discussed. Lastly, the development of flexible membrane based infrared sensors, highly influenced by the fire beetle, is presented, where a pneumatic mechanism and a thermal-expansion stress-mediated buckling-based mechanism are investigated. Other areas that are discussed include novel biological signal filtering mechanisms and reciprocal benefits offered through applying the biology lessons to engineered systems.