More Like this

1. Revealing chemistry-structure-function relationships in shark vertebrae across length scales

   https://doi.org/10.1016/j.actbio.2024.09.041  

   Raja_Somu, Dawn; Fuentes, Malena; Lou, Lihua; Agarwal, Arvind; Porter, Marianne; Merk, Vivian (September 2024, Acta Biomaterialia)

   Wagner, R William (Ed.)

   Shark cartilage presents a complex material composed of collagen, proteoglycans, and bioapatite. In the present study, we explored the link between microstructure, chemical composition, and biomechanical function of shark vertebral cartilage using Polarized Light Microscopy (PLM), Atomic Force Microscopy (AFM), Confocal Raman Microspectroscopy, and Nanoindentation. Our investigation focused on vertebrae from Blacktip and Shortfin Mako sharks. As typical representatives of the orders Carcharhiniformes and Lamniformes, these species differ in preferred habitat, ecological role, and swimming style. We observed structural variations in mineral organization and collagen fiber arrangement using PLM and AFM. In both sharks, the highly calcified corpus calcarea shows a ridged morphology, while a chain-like network is present in the less mineralized intermedialia. Raman spectromicroscopy demonstrates a relative increase of glucosaminocycans (GAGs) with respect to collagen and a decrease in mineral-rich zones, underlining the role of GAGs in modulating bioapatite mineralization. Region-specific testing confirmed that intravertebral variations in mineral content and arrangement result in distinct nanomechanical properties. Local Young's moduli from mineralized regions exceeded bulk values by a factor of 10. Overall, this work provides profound insights into a flexible yet strong biocomposite, which is crucial for the extraordinary speed of cartilaginous fish in the worlds’ oceans. 

   more » « less
2. Stretchable Laminates with Tunable Structural Colors from Layered Stacks of Elastomeric, Ionic, and Natural Polymers

   https://doi.org/10.1021/acsami.5c01880  

   Zhang, Yiming; Flouda, Paraskevi; Poliukhova, Valeriia; Stryutsky, Alexandr V; Shevchenko, Valery V; Tsukruk, Vladimir V (April 2025, ACS Applied Materials & Interfaces)

   Natural polymers such as plant-derived cellulose nanocrystals (CNCs) are renowned for color iridescence due to their internal helical organization but show modest stretchability and bending abilities because of the brittle nature of highly crystalline needle-like nanocrystals. Herein, we report the highly stretchable composite materials built from these nanocrystals and hyperbranched ionic polymers (bIPs) with terminal amine-terminated poly(N-isopropylacrylamide) (PNIPAM) stacked between elastomeric layers. These layered elastomeric composites preserve high mechanical stretchability of polyurethane outer layers up to 150%. Furthermore. The toughness increased manifold due to the sequential initiation and arresting of concurrent transversal cracks within the reinforcing central nanocomposite layer. Moreover, vivid structural colors of CNC helical organization preserved within these laminated composites show the ability to response to humidity and temperature. We suggest that these elastomeric composite laminates with preserved structural colors of helical nanocellulose organization can be considered as promising candidates for demanding applications, such as robust wearable sensors, flexible optical labels, and photonic devices. 

   more » « less
3. The load-bearing function of the colorectal submucosa and its relevance to visceral nociception elicited by mechanical stretch

   https://doi.org/10.1152/ajpgi.00127.2019  

   Siri, Saeed; Maier, Franz; Santos, Stephany; Pierce, David M; Feng, Bin (July 2019, American Journal of Physiology-Gastrointestinal and Liver Physiology)

   Mechanical distension beyond a particular threshold evokes visceral pain from distal colon and rectum (colorectum) and thus biomechanics plays a central role in visceral nociception. In this study we focused on the layered structure of the colorectum through the wall thickness and determined the biomechanical properties of layer-separated colorectal tissue. We harvested the distal 30 mm of mouse colorectum and dissected into inner and outer composite layers. The inner composite consists of the mucosa and submucosa while the outer composite includes the muscular layers and serosa. We divided each composite axially into three 10 mm-long segments and conducted biaxial mechanical extension tests and opening-angle measurements for each tissue segment. In addition, we quantified the thickness of the rich collagen network in the submucosa by nonlinear imaging via second harmonic generation (SHG). Our results reveal the inner composite is slightly stiffer in the axial direction while the outer composite is stiffer circumferentially. The stiffness of the inner composite in the axial direction is about twice that in the circumferential direction, consistent with the orientations of collagen fibers in the submucosa approximately ±30 degrees to the axial direction. Submucosal thickness measured by SHG showed no difference from proximal to distal colorectum under load-free condition, which likely contributes to the comparable tension stiffness of the inner composite along the colorectum. This, in turn, strongly indicates the submucosa as the load-bearing structure of the colorectum. This further implies nociceptive roles for the colorectal afferent endings in the submucosa that likely encode tissue-injurious mechanical distension. 

   more » « less
4. Second Harmonic Generation Imaging Reveals Entanglement of Collagen Fibers in the Elephant Trunk Skin Dermis

   https://doi.org/10.1101/2023.08.11.553031  

   Schulz, Andrew K; Plotczyk, Magdalena; Sordilla, Sophia; Boyle, Madeline; Singal, Krishma; Reidenberg, Joy S; Hu, David L; Higgins, Claire A (August 2023, bioRxiv)

   Abstract Form-function relationships often have tradeoffs: if a material is tough, it is often inflexible, and vice versa. This is particularly relevant for the elephant trunk, where the skin should be protective yet elastic. To investigate how this is achieved, we used classical histochemical staining and second harmonic generation microscopy to describe the morphology and composition of elephant trunk skin. We report structure at the macro and micro scales, from the thickness of the dermis to the interaction of 10μm thick collagen fibers. We analyzed several sites along the length of the trunk, to compare and contrast the dorsal-ventral and proximal-distal skin morphologies and compositions. We find the dorsal skin of the elephant trunk can have keratin armor layers over 2mm thick, which is nearly 100 times the thickness of the equivalent layer in human skin. We also found that the structural support layer (the dermis) of elephant trunk contains a distribution of collagen-I (COL1) fibers in both perpendicular and parallel arrangement. The bimodal distribution of collagen is seen across all portions of the trunk, and is dissimilar from that of human skin where one orientation dominates within a body site. We hypothesize that this distribution of COL1 in the elephant trunk allows both flexibility and load-bearing capabilities. Additionally, when viewing individual fiber interaction of 10μm thick collagen, we find the fiber crossings per unit volume are five times more common than in human skin, suggesting that the fibers are entangled. We surmise that these intriguing structures permit both flexibility and strength in the elephant trunk. The complex nature of the elephant skin may inspire the design of materials that can combine strength and flexibility. 

   more » « less
5. Epitaxial twin coupled microstructure in GeSn films prepared by remote plasma enhanced chemical vapor deposition

   https://doi.org/10.1063/5.0189718  

   Jiang, Jiechao; Chetuya, Nonso Martin; Ngai, Joseph H; Grzybowski, Gordon J; Meletis, Efstathios I; Claflin, Bruce (April 2024, Journal of Applied Physics)

   Growth of GeSn films directly on Si substrates is desirable for integrated photonics applications since the absence of an intervening buffer layer simplifies device fabrication. Here, we analyze the microstructure of two GeSn films grown directly on (001) Si by remote plasma-enhanced chemical vapor deposition (RPECVD): a 1000 nm thick film containing 3% Sn and a 600 nm thick, 10% Sn film. Both samples consist of an epitaxial layer with nano twins below a composite layer containing nanocrystalline and amorphous. The epilayer has uniform composition, while the nanocrystalline material has higher levels of Sn than the surrounding amorphous matrix. These two layers are separated by an interface with a distinct, hilly morphology. The transition between the two layers is facilitated by formation of densely populated (111)-coupled nano twins. The 10% Sn sample exhibits a significantly thinner epilayer than the one with 3% Sn. The in-plane lattice mismatch between GeSn and Si induces a quasi-periodic misfit dislocation network along the interface. Film growth initiates at the interface through formation of an atomic-scale interlayer with reduced Sn content, followed by the higher Sn content epitaxial layer. A corrugated surface containing a high density of twins with elevated levels of Sn at the peaks begins forming at a critical thickness. Subsequent epitaxial breakdown at the peaks produces a composite containing high levels of Sn nanocrystalline embedded in lower level of Sn amorphous. The observed microstructure and film evolution provide valuable insight into the growth mechanism that can be used to tune the RPECVD process for improved film quality. 

   more » « less