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Flat metasurfaces with subwavelength meta-atoms can be designed to manipulate the electromagnetic parameters of incident light and enable unusual light-matter interactions. Although hydrogel-based metasurfaces have the potential to control optical properties dynamically in response to environmental conditions, the pattern resolution of these surfaces has been limited to microscale features or larger, limiting capabilities at the nanoscale, and precluding effective use in metamaterials. This paper reports a general approach to developing tunable plasmonic metasurfaces with hydrogel meta-atoms at the subwavelength scale. Periodic arrays of hydrogel nanodots with continuously tunable diameters are fabricated on silver substrates, resulting in humidity-responsive surface plasmon polaritons (SPPs) at the nanostructure-metal interfaces. The peaks of the SPPs are controlled reversibly by absorbing or releasing water within the hydrogel matrix, the matrix-generated plasmonic color rendering in the visible spectrum. This work demonstrates that metasurfaces designed with these spatially patterned nanodots of varying sizes benefit applications in anti-counterfeiting and generate multicolored displays with single-nanodot resolution. Furthermore, this work shows system versatility exhibited by broadband beam-steering on a phase modulator consisting of hydrogel supercell units in which the size variations of constituent hydrogel nanostructures engineer the wavefront of reflected light from the metasurface.

Human lysophosphatidic acid receptor 1 (LPA1 ) is a G-protein coupled receptor that mediates various biological functions such as proliferation, platelet aggregation, smooth muscle contraction, and tumor cell invasion. For dissection of the molecular function of LPA1 , a recombinant LPA1 was overexpressed in Escherichia coli membrane fractions and purified to homogeneity by single affinity chromatography. The purified LPA1 was stabilized with an amphiphilic polymer that was synthesized by the coupling of octylamine, glucosamine, and diethylaminoproylamine at the carboxylic groups of poly-γ-glutamic acid. The complex of purified LPA1 and amphiphilic polymer showed a monodisperse oligomer and specific binding to LPA with apparent Ki values of 30 μM. Compared with the Gs protein, it also showed selective binding to the alpha subunit of the Gi protein. These results indicate that recombinant LPA1 in an amphiphilic polymer complex has an active conformation for interaction with ligands and G-proteins.

Difficulties in the extraction of membrane proteins from cell membrane and their solubilization in native conformations have hindered their structural and biochemical analysis. To overcome these difficulties, an amphipathic polypeptide was synthesized by the conjugation of octyl and glucosyl groups to the carboxyl groups of poly-γ-glutamic acid (PGA). This polymer, called amphipathic PGA (APG), self-assembles as mono-disperse oligomers consisted of 4–5 monomers. APG shows significantly low value of critical micelle concentration and stabilization activity toward membrane proteins. Most of the sodium dodecyl sulfate (SDS)-solubilized membrane proteins from Escherichia coli remain soluble state in the presence of APG even after the removal of SDS. In addition, APG stabilizes purified 7 transmembrane proteins such as bacteriorhodopsin and human endothelin receptor Type A (ETA) in their active conformations. Furthermore, ETA in complex with APG is readily inserted into liposomes without disrupting the integrity of liposomes. These properties of APG can be applied to overcome the difficulties in the stabilization and reconstitution of membrane proteins.

We have developed a high performance liquid crystal (LC) alignment layer of ultra-thin single wall carbon nanotubes (SWNTs) and a conjugated block copolymer nanocomposite that is solution-processible for conventional twisted nematic (TN) LC cells. The alignment layer is based on the non-destructive solution dispersion of nanotubes with a poly(styrene-b- paraphenylene) (PS-b-PPP) copolymer and subsequent spin coating, followed by conventional rubbing without a post-annealing process. Topographically grooved nanocomposite films with two dimensionally (2D) networked SWNTs embedded in a block copolymer matrix were created using a rubbing process in which bundles of SWNTs on the composite surface were effectively removed. The LCs were well aligned with a stable pre-tilt angle of approximately 2° on our extremely transparent nanocomposite, which gave rise to superfast switching of the TN LC molecules that was approximately 3.8 ms, or four times faster than that on a commercial polyimide layer. Furthermore, the TN LCD cells containing our SWNT nanocomposite alignment layers exhibited low power operation at an effective switching voltage amplitude of approximately 1.3 V without capacitance hysteresis.

This paper presents a novel green laser sequential lateral solidification G-SLS process for AMOLED applications. G-SLS utilizes a high frequency pulsed green laser and 2D mask patterns to manipulate the microstructure of crystallize Si films. Mask patterns have been optimized to obtain uniform microstructure of the crystallized Si films at the overlap region. Thin film transistors based on G-SLS processed Si films have mobility of 150.72 cm2/V-sec and a sub-threshold swing of 0.20V/dec. 14″ qFHD AMOLEDs have been fabricated using the G-SLS process. The advantages and issues of G-SLS technology will be further discussed.

For the first time, photo sensors employing p-type Si and IGZO semiconductor (P-I-OS) have been fabricated with a sensor dimension of W/L = 1600/5. The IGZO layer was deposited using DC sputtering and replaces the conventional n+-doped cathode electrode. The P-I-OS photo sensor is more sensitive to light with shorter wavelengths, and high to low photo-current dynamic range is almost constant from −15V to −2.5V of anode bias. The P-I-OS photo sensor exhibits dynamic range of 53.3 dB under −5V of anode bias and 10,000 lx of illuminated light intensity

This paper describes polymeric nanostructures with dynamically tunable wetting properties. Centimeter-scale areas of monolithic nanoridges can be generated by strain relief of thermoplastic polyolefin films with fluoropolymer skin layers. Changing the amount of strain results in polyolefin ridges with aspect ratios greater than four with controlled feature densities. Surface chemistry and topography are demonstrated to be able to be tailored by SF6 -plasma etching to access multiple wetting states: Wenzel, Cassie-Baxter, and Cassie-impregnating states. Reversible transitions among the wetting states can be realized in a programmable manner by cyclic stretching and reshrinking the patterned substrates without delamination and cracking.

Camptothecin (CPT) is a naturally occurring alkaloid that shows promise in antitumor activity in vitro against various tumor cell lines. Its potential clinical uses, however, are hindered by a lack of reaction selectivity and poor water solubility. Presented herein is a novel polyrotaxane (PR)-based delivery system that could potentially lead to a highly effective yet less toxic CPT therapy. The approach involves the synthesis of the PR-CPT conjugates via hydrolyzable linkages. To enhance the therapeutic efficacy of CPT, a cell-penetrating peptide, LMWP, is linked to the conjugate to allow specific, intratumoral delivery of CPT. To avoid nonselective uptake of the conjugates by normal tissues following administration, the cell-penetrating function of LMWP on the conjugates is masked by heparin binding. This system was designed such that after accumulation at the tumor via the enhanced permeability and retention (EPR) effect, protamine can be subsequently administered to unmask heparin inhibition on LMWP, permitting intracellular uptake of the LMWP-PR-CPT conjugates. Once inside the tumor, CPT molecules are detached from the PR chain by hydrolysis, yielding a sustained concentration of CPT within tumor cells. In this paper, we demonstrated the in vitro feasibility of this delivery system. The LMWP-PR-CPT conjugates yielded a sevenfold increase in the overall CPT solubility, as well as a sustained release of CPT over a period of more than 7 days. Intracellular uptake of these conjugates by A2780 human ovarian cancer cells and regulation of such uptake by heparin and protamine were tested by MTT assay and confocal/flow cytometric methods, respectively.

A new low power consumption amorphous silicon (a-Si:H) TFT level shifter is designed and verified by SPICE simulation. The a-Si:H TFT level shifter employing cascade inverters successfully shifts low voltage (5 V) to high voltage (23 V) by employing a bootstrapping method. Proposed a-Si:H TFT level shifter has considerably reduced the power consumption by 50% compared with the conventional one (8.03 mW) due to connection of clock pulse on the diode connected node and bootstrapping method. The proposed level shifter may be suitable for mobile display applications.

Highly stable voltage programmed a-Si:H TFT pixel circuit for AMOLED, which employs both Vth-compensation and negative bias annealing, is proposed and fabricated. Experimental results, after 60 hours electrical stress at elevated temperature (60°C) show that the OLED current stability in the proposed pixel is considerably improved compared with a conventional 2-TFT pixel, Vth-compensated pixel, and negative bias annealed pixel, respectively. The proposed pixel can reduce the degradation of a-Si:H TFT by employing negative bias annealing store Vth of a-Si:H TFT so that highly stable and uniform a-Si:H TFT backplane for AMOLED. Our proposed pixel may be suitable for highly stable AMOLED employing the a-Si:H TFT.

Highly porous poly(ethylene glycol) (PEG) hydrogel scaffolds crosslinked with hydrolyzable polyrotaxane for cartilage tissue engineering were prepared by a solvent casting/salt leaching technique. The resultant scaffolds have well interconnected microporous structures ranging from 87 to 90%. Pore sizes ranging from 115.5–220.9 μm appeared to be dependent on the size of the sieved sodium chloride particulates. Moreover, a dense surface skin layer was not found on either side of the scaffold surfaces. Using microscopic Alcian blue staining of the chondrocyte-seeded scaffolds, well adhered cells and newly produced glycosaminoglycans (GAG) were confirmed. Following the initial chondrocyte seeding onto the hydrogel scaffolds, the cell number was significantly increased, reaching 149, 877, and 1228 cells/mg of tissue at 8, 15, and 21 days in culture, respectively. The micrograph shows well adhered and spread chondrocytes in the interior pores and a cartilaginous extracellular matrix with a GAG fraction produced from the chondrocytes. Results suggest that the PEG hydrogel scaffolds crosslinked with the hydrolyzable polyrotaxane are a promising candidate for chondrocyte culture. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1087–1092, 2003

Poly(propylene glycol) (PPG)-grafted dextran was synthesized by conjugating amino-terminated PPG with hydroxyl groups of dextran, and its inclusion complexation property was investigated. The average number of grafted PPG per dextran was changeable in the range of 1.1 to 38.5. The formation of inclusion complexes between the PPG grafts and β-cyclodextrins (β-CDs) and their crystalline structures were characterized by 13 C CP/MAS NMR and X-ray spectroscopies. These hydrogel systems showed a thermall reversible sol-gel transition based on supramolecular assembly and dissociation between host and guest moieties. The results of theological measurements and solgel transition temperature of the hydrogels suggested that the aggregate channel-type crystalline domain was critical to control the transition temperature in terms of initial feed molar ratio of PPG and β-CD and the graft number of PPG constituents. These thermoreversible hydrogel systems showed rapid gelation properties, which may be useful for biomedical application, especially injectable drug deliver systems.

Novel functional polymers utilizing specific host/guest interactions were designed by introducing α-CD host molecules into poly(e-lysine) chains as side groups. An interesting phase separation was observed as a result of the inclusion complexation between the polymeric host and 3-(trimethylsilyl)propionic acid as a model guest in aqueous media. This water-soluble polymeric host would be useful for various applications, particularly drug delivery, due to its biodegradability, low toxicity, and unique functionality represented as a complexation-induced phase separation.

A novel chemical modification of biological tissues was developed aimed at improving biocompatibility and calcification resistance. This method involved the additional grafting of sulfonated PEO (PEO-SO(3)) or heparin after conventional glutaraldehyde (GA) fixation of bovine pericardium (BP). The amino groups of PEO-SO(3) or heparin were utilized to react to the GA residues to block them. The PEO-SO(3) or heparin grafted tissues demonstrated a slightly higher shrinkage temperature and tensile strength, but greater resistance to collagenase digestion, than GA treated ones. These results suggest that modified tissues have improved durability due to the grafting and filling effect of PEO-SO(3) or heparin in addition to the GA cross-linking. At the direct contact cytotoxicity test in vitro, PEO-SO(3) or heparin grafted tissue was shown to be nontoxic, while relatively significant cytotoxicity was observed for the GA treated tissues, possibly due to the release of GA. From the in vivo calcification study, calcium contents deposited on the modified tissues were much less than those on GA treated tissues. Such a decreased calcification might be explained by the decrease of residual GA groups during the additional treatment, and the space-filling effect and the nonadhesive property and/or the blood compatibility of PEO-SO(3) or heparin grafted covalently. The newly modified tissue patch was observed to show improved pathological assessibility including less inflammation and tissue reactions. This simple modification method may be useful for calcification-resistant and blood-compatible tissue patches for cardiovascular implants.

Polyethylene oxide (PEO) surfaces were prepared by the addition of PEO- and sulfonated PEO-containing amphiphilic block copolymers as surface-modifying additives in a segmented polyurethane (PU). PEO-PPO-PEO triblock copolymers (Pluronics) with different PEO chain lengths (from 2 to 80) were used as additives. The prepared film surfaces were characterized by the measurement of dynamic water contact angles and electron spectroscopy for chemical analysis. It was observed that the PU films containing 10 wt % of PEO additives were surface-saturated with the additives regardless of their PEO chain length, but the PEO chains were more projected from the film surfaces containing the additives with longer PEO chains. The water absorption of the films increased largely with the increasing PEO chain length of the additives. The addition of PEO additives produced film surfaces that were in a gel-like state. The films demonstrated some extraction of the PEO additives. However, the additives with higher molecular weights were entrapped more stably into the PU matrix. The mechanical properties (tensile strength and elongation) of the films were changed by the addition of PEO additives, but the differences were not significant compared to the control PU. The platelet adhesion on the film surfaces decreased with increasing PEO chain length of the additives. The film surface containing additives with long PEO chains (chain length of 80) was particularly effective in preventing platelet adhesion. The effect of negatively charged sulfonate groups on the prevention of platelet adhesion appeared only on the film surfaces containing additives with short PEO chains. For longer PEO chains, the chain mobility effect was more dominant than the negative charge effect on the prevention of platelet adhesion. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 314–323, 1998.

An excimer-laser-based two-shot sequential lateral solidification (TS-SLS) process has been developed to fabricate 30” FHD (1920×RGB×1080) AMOLED TVs using both 2D projection and line-scan SLS systems. We have optimized (1) the microstructure of TS-SLS processed polycrystalline materials, (2) the geometry of driving TFTs to minimize non-uniformity of the pixel brightness and (3) the off-bias TFT aging process to reduce the leakage current. This result verifies that the TS-SLS process can be utilized to make large area AMOLED TVs without any laser related mura.

— An asymmetric source/drain offset structured (AOS) polycrystalline-silicon (poly-Si) thin-film transistor (TFT) has ben developed by employing alternating magnetic-field-enhanced rapid thermal annealing (AMFERTA). The realized AOS poly-Si TFT, with long drain-side offset length LOff1 and short source-side offset length LOff2, considerably suppresses leakage current without sacrificing ON-current. The offset regions of the AOS TFT are naturally lightly doped due to the diffusion of n+ ions by AMFERTA crystallization. The fabrication process of the AOS TFT does not require any additional offset mask step or doping process. Experimental results show that the leakage current is considerably suppressed when the drain-side offset length LOff1 is larger than 1.25 μm.

We have designed and fabricated a new top gate asymmetric offset structured n-type depletion mode poly-Si TFT of which the leakage current was considerably reduced due to successful suppression of electric field near the drain region caused by the asymmetric offset structure. The TFT was fabricated on the glass substrate by employing alternating magnetic field enhanced rapid thermal annealing (AMFERTA). The a-Si and n+ a-Si layers were deposited successively, and did not use any other ion doping methods. The asymmetric offset structure could be made without additional processes or masks. This new structure suppressed the leakage current to about 86% of non-offset structured AMFERTA poly-Si TFT without considerable sacrifice of on current. This suppression method of leakage current can be helpful to remain the good image quality and save the power consumption of AMOLED panels.

— The temperature dependence of the hysteresis of an a-Si:H TFT has been investigated. An a-Si:H TFT pixel driving scheme has been proposed and investigated. This scheme can eliminate changes in the organic light-emitting diode (OLED) current caused by hysteresis of an a-Si:H TFT. The VTH of the a-Si:H TFT was changed according to the gate-voltage sweep direction because of the hysteresis of the a-Si:H TFT. The variation of VTH for a a-Si:H TFT decreased from 0.41 to 0.17 V at an elevated temperature of 60°C because the sub-threshold slope (s-slope) of the a-Si:H TFT, in the reverse voltage sweep direction, increased more than in the forward voltage sweep direction due to a greater increase in the initial electron trapped charges than the hole charges. Although the OLED current variation caused by hysteresis decreased (∼14%) as the temperature increased, the error in the OLED current needed to be improved in order to drive the pixel circuit of AMOLED displays. The proposed pixel circuit can apply the reset voltage (−10 V) before the data voltage for the present frame that was written to fix the sweep direction of the data voltage. The variation in the OLED current caused by hysteresis of the a-Si:H TFT was eliminated by the fixed voltage sweep direction in the proposed pixel circuit regardless of operating temperature.

We developed an a-Si TFT-LCD panel with integrated gate driver circuit using a standard 5-MASK process. To minimize the effect of the a-Si TFT current and LC's capacitance variation with temperature, we developed a new a-Si TFT circuit structure and minimized coupling capacitance by changing vertical architecture above gate driver circuit. Integration of gate driver circuit on glass substrate enables single chip and 3-side free panel structure in a-Si TFT-LCD of QVGA(240*320) resolution.

The temperature-dependent enzymatic degradation of semi-IPN hydrogels consisting of dextran grafted with thermo-responsive chains (lower cloud point) and a thermo-responsive crosslinked matrix (higher cloud point) was examined. Enzymatic degradation of the semi-IPN hydrogel was significantly inhibited below the lower and above the higher cloud point. Only between both cloud points, enzymatic degradation proceeded. The designed semi-IPN hydrogel is therefore advantageous to achieve enzymatic degradation at a specific temperature range.