Advanced Materials Technologies最新文献

Nanocomposites made from alginate and nanoclay are extensively applied for diverse biomedical applications. However, the lack of a clear understanding of the interactions between alginate and nanoclay makes it difficult to rationally design the nanocomposites for different material extrusion-based 3D bioprinting strategies. Here, a combined analytical model is proposed to accurately predict the interaction mechanisms between alginate and nanoclay through small-angle neutron scattering. These mechanisms are summarized into a phase diagram that can guide the design of alginate-nanoclay nanocomposites for different bioprinting applications. The rheological properties of various nanocomposites are measured to validate the proposed interaction mechanisms at the macroscale. Accordingly, three representative extrusion-based bioprinting strategies are linked with the nanocomposite design and applied to freeform fabricate complex structures. A roadmap is summarized to bridge the gap between biomaterial design and bioprinting processes, enabling the rapid and rational selection of biomaterial formula based on available 3D printing methods, and vice versa.

This work presents the development of fully printed, large-area, semi-transparent Dye-Sensitized Solar Cells (DSSCs) using TiO₂ nanoparticles treated with TiCl₄, a “D35” push-pull dye sensitizer, and I₃⁻/I⁻ redox mediator. Cells with areas of 4 and 200 cm² were printed using hexagonal, stripe, and standard designs, employing digital materials deposition (DMD) technology. The porous films printed via DMD, confirmed by scanning electron microscopy (SEM), improved solar cells performance by enhancing the Open Circuit Voltage (Voc) and fill factor (FF). The hexagonal design, in particular, facilitated better electrolyte impregnation in the TiO₂ mesoporous structure, boosting current density. This design yielded a power conversion efficiency (PCE) of 7.05% for 4 cm² DSSCs, surpassing the stripe (5.50%) and standard (5.48%) designs. Its higher performance can be attributed to lower interfacial charge recombination rates and improvedcharge transfer and collection efficiency. Photophysical measurements indicated faster charge transfer rates in hexagonal cells (≈ 1.3  ×  10⁹s⁻¹) compared to the stripe (9.8  ×  10⁸ s⁻¹) and standard (9.5  ×  10⁸ s⁻¹) designs. Hence, our work highlights the potential of hexagonal design to improve both efficiency and transparency while reducing material consumption, offering a promising approach for manufacturing semi-transparent solar cells.

Ocean wave energy is one of the most promising green energies in the wild. However, it is still challenging to effectively collect wave energy due to its randomness and irregularity. In this work, a kelp inspired high-power density triboelectric nanogenerator (K-TENG) is presented for harvesting wave energy with characteristics in multiple directions. The proposed K-TENG consists of a series of stacked leaf-like units. The influence of configuration parameters, including pellet diameters, pellet numbers, unit sizes, oscillation frequency, swing amplitude, and wave directions on output performances of leaf-like units, are extensively investigated. Experimental data indicates that a single leaf-like unit can achieve a maximum output voltage of 623.14 V as well as a maximum current of 1.48 µA and realize energy harvesting from different wave directions. A K-TENG composed of 15 leaf-like units demonstrates a high-power density of 18.77 W m⁻³ at a wave frequency of 2.5 Hz, which successfully powers a digital watch and 414 light-emitting diodes (LEDs). This work is hoped to provide a simple and reliable route to effectively harvest ocean wave energy.

Shape memory polymers (SMPs) have been extensively investigated because of their wide range of biomedical and robot applications. In most of SMPs, only one temporary shape can be formed and recovered through the mechanism of melting or glass transition. Herein, a multiple shape memory effect (mSME), i.e., formation of at least two temporary shapes, can be realized in polyvinylidene fluoride (PVDF)-based ferroelectric polymers by exploiting their expanded ferroelectric–paraelectric (F-P) phase transition temperature range. Although P(VDF-TrFE) (TrFE: trifluoroethylene) (55/45) copolymer is thought to be a normal ferroelectric, its ferroelectric phase transforms into a paraelectric phase through an intermediate relaxor ferroelectric-like state and mSME is observed in this extended phase transition temperature range. By incorporating CTFE (chlorotrifluoroethylene) into P(VDF-TrFE), P(VDF-TrFE-CTFE) becomes a relaxor ferroelectric with a further extended phase transition temperature range. The terpolymer exhibits improved mSME and at least three temporary shapes can be formed and recovered. A comparison of SME and structures of several PVDF-based copolymer and terpolymers suggests that the amount of polar phase is a critical factor affecting the SME. This study not only demonstrates mSME in ferroelectric polymers, which expands their application potential, but also provides an in-depth understanding of the shape memory mechanism of the polymers.

Inflatable pouches are attractive as actuators and structural links in soft robots due to their low deflated profile and high deformation ratio. However, current pouch robot fabrication methods have relatively large minimum feature sizes and multi-layer fabrication challenges, limiting the integration of mechanisms with many independent degrees of freedom (DoF). A new monolithic prototype fabrication method utilizes inkjet printing of a masking ink layer, which prevents film bonding and thus defines inflatable regions. Multi-layer inflatable pouches of any planar geometry can be created using thermal fusing, with inter-layer connections and a minimum feature resolution of 0.3 mm. The multi-layer fabrication process enables the integration of pouches for bending actuation and structure, pneumatic channels, and external port connections. This high level of integration enables the fabrication of pouch robots with many independent DoFs. Specific examples using four layers of 38 micrometer thick Low-density polyethylene (LDPE) include 1) a 38 mm-wide 4-fingered robot hand with 8 independent DoFs which rotates a cube within its palm and 2) a 138 mm-long planar continuum manipulator with 10 independent DoFs for pick-and-place of a cylinder. These example designs demonstrate the capability of ink-patterned masking to achieve new levels of functionality for thin-film pouch robots.

Monitoring the cardiovascular health of patients and early diagnosis of heart diseases are highly sought after as they can represent a true cornerstone in tomorrow's healthcare surveillance. Here, an unprecedented non-invasive device prototype is reported for pulse wave velocity (PWV) measurement based on a piezoelectric graphene pressure sensor. PWV is a critical health indicator that estimates arterial stiffness by measuring the velocity of arterial pulse flow through the circulatory system. The sensor incorporates advanced electronic components and data analysis tools, enabling the measurement of pulse transit time (PTT), that is the time required for the pulse wave to travel between carotid and femoral artery sites. Significantly, the outcomes obtained through the novel method, which involved monitoring 10 patients within clinical environment, show statistical similarity to results obtained using established technology for the PWV estimation such as SphygmoCor. In particular, the mean difference between measurements done with the two techniques resulted in 0.1 m s⁻¹, that is <2%, underscoring the reliability of the novel device. The technology holds big promise for enhancing cardiovascular healthcare delivery: it is wearable, potentially exploitable by a non-expert user, and it needs to be powered with just 0.2 V, thus it can become compatible even with applications in point-of-care settings.

The functional principle behind extrusion-based printing is the capability of flowing material through a nozzle on demand, which must solidify upon deposition, a behavior exhibited only by some materials. Embedded printing offers a solution to maintain shape fidelity during the deposition of a wider range of materials. However, the use of a moving nozzle in a support bath can lead to bath disturbance and the spreading of the ink. In this study, a novel embedded printing technique that eliminates the need for a nozzle by employing a magnetic sphere as the plotting moiety is introduced. The externally steered sphere creates a path by locally fluidizing the bath, allowing the simultaneously injected ink to flow into the space behind it. The method is benchmarked using water as an ink, achieving free-form printing without additional stabilization methods. The creation of solid structures is also demonstrated by printing a photocurable ink that is crosslinked and removed from the bath. Moreover, the plotting magnet can be incorporated into the printed part during the crosslinking, thus giving place to a magnetically responsive structure. This advancement paves the way for innovations in fields such as tissue engineering and microrobotics by enabling the fabrication of intricate and functional designs.

Memristors-based neuromorphic devices represent emerging computing architectures to perform complex tasks by outpacing the traditional Von-Neumann architectures in terms of speed, and energy efficiency. In this work, the resistive switching (RS) behavior of sol-gel grown and ion-irradiated BFO films is investigated under electrical stimulus. The Ag/BFO/FTO memristors emulate a combination of digital and analog RS behavior within a single device. The possible mechanism of analog digital hybridity is addressed by considering the formation of the conducting filament by oxygen vacancies, Ag⁺ ions and Schottky barrier height modulation. The ion-irradiated BFO samples are analyzed using the Raman, XRD, and XPS studies. To uphold bioinspired synaptic actions, crucial synaptic functionalities like pair-pulse facilitation and long-term potentiation/depression are effectively achieved. More intricate synaptic behaviors are also demonstrated such as spike-time-dependent plasticity and Pavlovian classical conditioning, which represent the prominent attributes of both learning and forgetting behavior. Additionally, high pattern recognition accuracy (96.1%) is achieved in an artificial neural network simulation by using the synaptic weights of the memristors. This synergistic effect of digital and analog RS in ion-irradiated BFO can be beneficial for the emulation of complex learning behavior as well as its incorporation into low-power neuromorphic computing.

Fused Filament Fabrication is a promising manufacturing technology for the circularity of space missions. Potential scenarios include in-orbit applications to maximize mission life and to support long-term exploration missions with in situ manufacturing and recycling. However, its adoption is restricted by the availability of engineering polymers displaying mechanical performance combined with resistance to space conditions. Here, a thermotropic Liquid Crystal Polymer (LCP) is reported as a candidate material with extrusion 3D printing. To expand its scope of applicability to structural parts for space applications, four different exposure conditions are studied: thermal cycling under vacuum, atomic oxygen, UV, and electron irradiations. While 1 MeV-electron irradiation leads to a green coloration due to annealable color centers, the mechanical performance is only slightly decreased in dynamic mode. It is also found that increased printing temperature improves transverse strength and resistance to thermal cycling with the trade-off of tensile stiffness and strength. Samples exposed to thermal cycling and the highest irradiation dose at lower printing temperatures still display a Young's modulus of 30 GPa and 503 MPa of tensile strength which is exceptionally high for a 3D-printed polymer. For the types of exposure studied, overall, the results indicate that LCP 3D-printed parts are well suited for space applications.

Three billion years of evolution have produced a vast variety of protein molecules, whose functions are directly dependent on their ability to assume and maintain specific shapes. Proteins are defined by the sequence and chemical characteristics of their amino acids, which dictate their 3D shape and function, ranging from enzymatic activity to immune responses. Here, we explore a synthetic form of linear structure that can be bent in a programmable way into various specific 3D shapes inspired by the way functional proteins are defined using genetic codes. This synthetic structure is based on non-circular multistable corrugated tubes, which can be fabricated at various length scales and cross-sectional shapes, thus enabling the modification of their properties. Additionally, the cross-section shape can be rewritten multiple times, allowing for the repair of structural damage and the rewriting of the properties of the structure's multi-stability. A numerical model is used to describe the bending energy landscape of different cross-sections. The proposed reprogrammable 3D shapes of a rewritable 1D metamaterial are promising candidates for futuristic robotic systems, complex deployable structures, catheter devices, and energy absorption and harvesting.