Multimaterial Printing for Cephalopod-Inspired Light-Responsive Artificial Chromatophores.

Cephalopods use chromatophores distributed on their soft skin to change skin color and its pattern. Each chromatophore consists of a central sac containing pigment granules and radial muscles surrounding the sac. The contraction of the radial muscle causes the central sac to expand in area, making the color of the pigment more visible. With the chromatophores actuating individually, cephalopods can create extremely complex skin color patterns, which they utilize for exquisite functions including camouflage and communication. Inspired by this mechanism, we present an artificial chromatophore that can modulate its color pattern in response to light. Multimaterial projection microstereolithography is used to integrate three functional components including a photoactive hydrogel composite with polydopamine nanoparticles (PDA-NPs), acrylic acid hydrogel, and poly(ethylene glycol) diacrylate. In order to generate light-driven actuation of the artificial chromatophore, the photothermal effect of the PDA-NPs, light-responsive deformation of the photoactive hydrogel composite, and the produced mechanical stresses are studied. Mechanical properties and interfacial bonding strengths between different materials are also investigated to ensure structural integrity during actuation. We demonstrate pattern modulation of the light-responsive artificial chromatophores (LACs) with the projection of different light patterns. The LAC may suggest a new concept for various engineering applications such as the camouflage interface, biophotonic device, and flexible display.

Self-Limiting Electrospray Deposition for the Surface Modification of Additively Manufactured Parts.

Electrospray deposition (ESD) is a spray coating process that utilizes a high voltage to atomize a flowing solution into charged microdroplets. These self-repulsive droplets evaporate as they travel to a target substrate, depositing the solution solids. Our previous research investigated the conditions necessary to minimize charge dissipation and deposit a thickness-limited film that grows in area over time through self-limiting electrospray deposition. Such sprays possess the ability to conformally coat complex three-dimensional (3D) objects without changing the location of the spray needle or orientation of the object. This makes them ideally suited for the postprocessing of materials fabricated through additive manufacturing (AM), opening a paradigm of independent bulk and surface functionality. Having demonstrated 3D coating with film thickness in the range of 1-50 µm on a variety of conductive objects, in this study, we employed model substrates to quantitatively study the technique's limits with regard to geometry and scale. Specifically, we examined the effectiveness of thickness-limited ESD for coating recessed features with gaps ranging from 50 µm to 1 cm, as well as the ability to coat surfaces hidden from the line-of-sight of the spray needle. This was then extended to the coating of hydrogel structures printed by AM, demonstrating that coating could be conducted even into the body of the structures as a means to create hydrophobic surfaces without affecting the absorption-driven humidity response. Further, these coatings were robust enough to create superhydrophobicity in the entire structure, causing it to resist immersion in water.

Clinical implication of tumor site in terms of node metastasis for intrahepatic cholangiocarcinoma.

BACKGROUND: The clinical implication of lymph node (LN) dissection of intrahepatic cholangiocarcinoma (ICCA) is still controversial, and LN metastasis (LNM) based on tumor site has not been confirmed yet. METHODS: Patients who underwent curative-intent surgery at 10 tertiary referral centers were identified and divided into peripheral (PP) and near second confluence level tumor (NC) groups on the basis of the distance from the second confluence and oncological outcomes were compared. RESULTS: Of 179 patients, 121 patients with LND were divided into the NC (n = 89) and PP groups (n = 32) on the basis of 4.5 cm from the second confluence. NC group showed higher LNM rate than PP group (46.1 vs 21.9%, p = 0.016) and NC was a risk factor for LNM (odds ratio: 4.367; 95% confidence interval: 1.234-15.453, p = 0.022). The 5-year overall survival (OS) rate (38.0% vs. 27.8%, p = 0.777) and recurrence-free survival (RFS) rates (22.8% vs. 25.8%, p = 0.742) showed no differences between the PP and NC groups. In the NC group, N1 patients showed worse 5-year OS (12.7% vs 39.0%, p = 0.004) and RFS (8.8% vs 28.6%, p = 0.004) than the N0 patients. In the PP group, discordant results in 5-year OS (48.9% vs. 50.0%, p = 0.462) and RFS (41.3% vs. 0%, p = 0.056) were found between the N0 and N1 patients. CONCLUSION: The NC group was an independent risk factor for LNM and LNM worsened prognosis in NC group for ICCA. In the PP group, LND should not be omitted because of high LNM rate and insufficient oncologic evidence.

Discrimination, Mental Disorders, and Suicidal Ideation in Latino Adults: Decomposing the Effects of Discrimination.

Experiences of discrimination and mental disorder have been recognized as risks for suicidality. Yet, few studies have examined the direct and indirect effects of discrimination on suicidal ideation through mental disorder among Latino adults in the U.S. This study aimed to examine whether everyday discrimination and racial/ethnic discrimination is associated with suicidal ideation and if mental disorder (i.e., DSM-IV depressive, anxiety, and substance use) mediates the association. Discrimination was operationalized with self-reported discriminatory experience. This study applied a mediation analysis to the data from National Latino and Asian American Survey, 2002-2003. The key findings are: (a) everyday discrimination had an independent association with suicidal ideation as well as exerted an indirect effect through anxiety disorder. (b) Racial/ethnic discrimination was not directly associated with suicidal ideation, but its adverse effect on suicidal ideation was mediated by the depressive disorder.

Soft Robotic Manipulation and Locomotion with a 3D Printed Electroactive Hydrogel.

Electroactive hydrogels (EAH) that exhibit large deformation in response to an electric field have received great attention as a potential actuating material for soft robots and artificial muscle. However, their application has been limited due to the use of traditional two-dimensional (2D) fabrication methods. Here we present soft robotic manipulation and locomotion with 3D printed EAH microstructures. Through 3D design and precise dimensional control enabled by a digital light processing (DLP) based micro 3D printing technique, complex 3D actuations of EAH are achieved. We demonstrate soft robotic actuations including gripping and transporting an object and a bidirectional locomotion.

Micro 3D Printing of a Temperature-Responsive Hydrogel Using Projection Micro-Stereolithography.

Stimuli-responsive hydrogels exhibiting physical or chemical changes in response to environmental conditions have attracted growing attention for the past few decades. Poly(N-isopropylacrylamide) (PNIPAAm), a temperature responsive hydrogel, has been extensively studied in various fields of science and engineering. However, manufacturing of PNIPAAm has been heavily relying on conventional methods such as molding and lithography techniques that are inherently limited to a two-dimensional (2D) space. Here we report the three-dimensional (3D) printing of PNIPAAm using a high-resolution digital additive manufacturing technique, projection micro-stereolithography (PµSL). Control of the temperature dependent deformation of 3D printed PNIPAAm is achieved by controlling manufacturing process parameters as well as polymer resin composition. Also demonstrated is a sequential deformation of a 3D printed PNIPAAm structure by selective incorporation of ionic monomer that shifts the swelling transition temperature of PNIPAAm. This fast, high resolution, and scalable 3D printing method for stimuli-responsive hydrogels may enable many new applications in diverse areas, including flexible sensors and actuators, bio-medical devices, and tissue engineering.

Terahertz polarization spectroscopy in the near-field zone of a sub-wavelength-scale metal slit.

Time-domain spectroscopy is used to probe the polarization dependence of the terahertz-frequency absorption of α-lactose molecules in the near-field vicinity of a sub-wavelength-scale metal slit. The experimental result finds that the 0.53-THz absorption of this material has an unexpected polarization dependence, strongly coupled to the slit orientation; in particular, the electric wave in parallel polarization exhibits even complete vanishing of the otherwise resonant strong absorption. The physics behind this phenomena may be explained based on the Bethe's sub-wavelength diffraction: the electric field that is measured in the far field, but diffracted from a sub-wavelength-scale metal aperture, originates from solely magnetic dipole radiation and not from the electric dipole radiation, thus showing no electrically-coupled material response.

Enzymatic size control of RNA particles using complementary rolling circle transcription (cRCT) method for efficient siRNA production.

A novel fabrication method for RNA particles (RPs) was developed based on enzymatic polymerization, and the size of the RPs was controlled intentionally by adjusting the RNA polymerase concentration for a variety of potential applications.

Self-assembly of free-standing RNA membranes.

RNA has emerged as a promising material for nanostructure and microstructure engineering. Although rare, some macroscopic RNA structures have also been constructed using lipid or polymer materials. Here, we report the first example of an enzymatically generated RNA membrane. This robust and free-standing RNA membrane has a macroscopic structure and is generated without any polymer support or complexation. Our RNA membrane is fabricated following two sequential processes, complementary rolling circle transcription and evaporation-induced self-assembly, and its structural and functional properties are rationally controlled by adjusting RNA base pairing. In this study, three types of RNA membranes are fabricated and are used to demonstrate potential applications.

Aptamer-based microspheres for highly sensitive protein detection using fluorescently-labeled DNA nanostructures.

Many highly sensitive protein detection techniques have been developed and have played an important role in the analysis of proteins. Herein, we report a novel technique that can detect proteins sensitively and effectively using aptamer-based DNA nanostructures. Thrombin was used as a target protein and aptamer was used to capture fluorescent dye-labeled DNA nanobarcodes or thrombin on a microsphere. The captured DNA nanobarcodes were replaced by a thrombin and aptamer interaction. The detection ability of this approach was confirmed by flow cytometry with different concentrations of thrombin. Our detection method has great potential for rapid and simple protein detection with a variety of aptamers.

Multiplexing enhancement for the detection of multiple pathogen DNA.

Various methods for the detection of pathogens have been researched and developed. However, most of detection methods are cost-ineffective and laborious. To minimize costs and labor, multi-detection of pathogen have been widely used. In this paper, we propose a novel multi-detection method, which can enhance multi-detection capability using fluorescent dye labeled DNA nanostructures that is named DNA nanobarcodes. By using three fluorescence colors, multi-detection capability is significantly increased because of the increased combination of three colors. Moreover, our approach uses a relatively simple DNA nanostructure to precisely control the fluorescence intensity ratio. Therefore, high multi-detection ability is achieved without constructing a complicated DNA nanostructure probe. Our novel detection method can overcome the obstacles of conventional methods and enhance multi-detection capability effectively. By using our new system, we were able to successfully detect nine different DNA pathogens simultaneously. Our system can easily increase the multiplexibility by using more fluosrescent colors on DNA nanobarcode.

Self-assembled DNA-based giant thrombin nanoparticles for controlled release.

Protein-aptamer interactions have been used in a wide range of fields, including medical diagnosis and protein delivery. Herein, we report a method for thrombin delivery with thrombin-binding aptamer (TBA), which is one of the well-known aptamers for thrombin, by generating giant thrombin nanoparticles (GTNPs). GTNPs can be synthesized by crosslinking thrombin with DNA nanostructures that possess several TBA molecules. To generate GTNPs, two different DNA nanostructures were used. Y-shaped DNA with TBA and X-shaped DNA with TBA were used for 250 and 650 nm GTNPs, respectively. Controlled release of thrombin from GTNPs was performed by adding complementary DNA (cDNA) to TBA. To investigate thrombin release from GTNPs, the sizes of the GTNPs were measured using dynamic light scattering, atomic force microscopy (AFM), and scanning electron microscopy (SEM). We confirmed a decrease in the size of GTNPs with various concentrations of cDNA, suggesting the release of thrombin. Based on these results, we expect that our method can be used to control the amount of thrombin released effectively. Our method is also widely applicable for effective protein delivery.

Terahertz lens made out of natural stone.

Terahertz (THz) time-domain spectroscopy probes the optical properties of naturally occurring solid aggregates of minerals, or stones, in the THz frequency range. Refractive index and extinction coefficient measurement reveals that most natural stones, including mudstone, sandstone, granite, tuff, gneiss, diorite, slate, marble, and dolomite, are fairly transparent for THz frequency waves. Dolomite in particular exhibits a nearly uniform refractive index of 2.7 over the broad frequency range from 0.1 to 1 THz. The high index of refraction allows flexibility in lens designing with a shorter accessible focal length or a thinner lens with a given focal length. Good agreement between the experiment and calculation for the THz beam profile confirms that dolomite has high homogeneity as a lens material, suggesting the possibility of using natural stones for THz optical elements.