Autonomous self-burying seed carriers for aerial seeding.

Aerial seeding can quickly cover large and physically inaccessible areas1 to improve soil quality and scavenge residual nitrogen in agriculture2, and for postfire reforestation3-5 and wildland restoration6,7. However, it suffers from low germination rates, due to the direct exposure of unburied seeds to harsh sunlight, wind and granivorous birds, as well as undesirable air humidity and temperature1,8,9. Here, inspired by Erodium seeds10-14, we design and fabricate self-drilling seed carriers, turning wood veneer into highly stiff (about 4.9 GPa when dry, and about 1.3 GPa when wet) and hygromorphic bending or coiling actuators with an extremely large bending curvature (1,854 m-1), 45 times larger than the values in the literature15-18. Our three-tailed carrier has an 80% drilling success rate on flat land after two triggering cycles, due to the beneficial resting angle (25°-30°) of its tail anchoring, whereas the natural Erodium seed's success rate is 0%. Our carriers can carry payloads of various sizes and contents including biofertilizers and plant seeds as large as those of whitebark pine, which are about 11 mm in length and about 72 mg. We compare data from experiments and numerical simulation to elucidate the curvature transformation and actuation mechanisms to guide the design and optimization of the seed carriers. Our system will improve the effectiveness of aerial seeding to relieve agricultural and environmental stresses, and has potential applications in energy harvesting, soft robotics and sustainable buildings.

Plant-Actuated Micro-Nanorobotics Platforms: Structural Designs, Functional Prospects, and Biomedical Applications.

Plants are anatomically and physiologically different from humans and animals; however, there are several possibilities to utilize the unique structures and physiological systems of plants and adapt them to new emerging technologies through a strategic biomimetic approach. Moreover, plants provide safe and sustainable results that can potentially solve the problem of mass-producing practical materials with hazardous and toxic side effects, particularly in the biomedical field, which requires high biocompatibility. In this review, it is investigated how micro-nanostructures available in plants (e.g., nanoparticles, nanofibers and their composites, nanoporous materials, and natural micromotors) are adapted and utilized in the design of suitable materials for a micro-nanorobot platform. How plants' work on micro- and nanoscale systems (e.g., surface roughness, osmotically induced movements such as nastic and tropic, and energy conversion and harvesting) that are unique to plants, can provide functionality on the platform and become further prospective resources are examined. Furthermore, implementation across organisms and fields, which is promising for future practical applications of the plant-actuated micro-nanorobot platform, especially on biomedical applications, is discussed. Finally, the challenges following its implementation in the micro-nanorobot platform are also presented to provide advanced adaptation in the future.

Magnetotransport in hybrid InSe/monolayer graphene on SiC.

The magnetotransport properties of a hybrid InSe/monolayer graphene in a SiC system are systematically studied. Compared to those of its bare graphene counterpart, in InSe/graphene, we can effectively modify the carrier density, mobility, effective mass, and electron-electron (e-e) interactions enhanced by weak disorder. We show that in bare graphene and hybrid InSe/graphene systems, the logarithmic temperature (lnT) dependence of the Hall slope R H = Î´R xy /δB = Î´ρ xy /δB can be used to probe e-e interaction effects at various temperatures even when the measured resistivity does not show a lnT dependence due to strong electron-phonon scattering. Nevertheless, one needs to be certain that the change of R H is not caused by an increase of the carrier density by checking the magnetic field position of the longitudinal resistivity minimum at different temperatures. Given the current challenges in gating graphene on SiC with a suitable dielectric layer, our results suggest that capping a van der Waals material on graphene is an effective way to modify the electronic properties of monolayer graphene on SiC.

Graphene Quantum Hall Effect Devices for AC and DC Electrical Metrology.

A new type of graphene-based quantum Hall standards is tested for electrical quantum metrology applications at alternating current (ac) and direct current (dc). The devices are functionalized with Cr(CO)3 to control the charge carrier density and have branched Hall contacts based on NbTiN superconducting material. The work is an in-depth study about the characteristic capacitances and related losses in the ac regime of the devices and about their performance during precision resistance measurements at dc and ac.

Mushroom-Derived Bioactive Molecules as Immunotherapeutic Agents: A Review.

Mushrooms with enhanced medicinal properties focus on finding such compounds that could modulate the human body's immune systems. Mushrooms have antimicrobial, antidiabetic, antiviral, hepatoprotective, antitumor, and immunomodulatory properties due to the presence of various bioactive components. ß-glucans are the major constituent of the mushroom cell wall and play a significant role in their biological activity. This review described the techniques used in the extraction of the active ingredients from the mushroom. We highlighted the structure of the bioactive polysaccharides present in the mushrooms. Therapeutic applications of different mushrooms were also described. It is interesting to note that mushrooms have the potential sources of many bioactive products that can regulate immunity. Thus, the development of functional medicinal food based on the mushroom is vital for human welfare.

Graphene Oxide-Based Stimuli-Responsive Platforms for Biomedical Applications.

Graphene is a two-dimensional sp2 hybridized carbon material that has attracted tremendous attention for its stimuli-responsive applications, owing to its high surface area and excellent electrical, optical, thermal, and mechanical properties. The physicochemical properties of graphene can be tuned by surface functionalization. The biomedical field pays special attention to stimuli-responsive materials due to their responsive abilities under different conditions. Stimuli-responsive materials exhibit great potential in changing their behavior upon exposure to external or internal factors, such as pH, light, electric field, magnetic field, and temperature. Graphene-based materials, particularly graphene oxide (GO), have been widely used in stimuli-responsive applications due to their superior biocompatibility compared to other forms of graphene. GO has been commonly utilized in tissue engineering, bioimaging, biosensing, cancer therapy, and drug delivery. GO-based stimuli-responsive platforms for wound healing applications have not yet been fully explored. This review describes the effects of different stimuli-responsive factors, such as pH, light, temperature, and magnetic and electric fields on GO-based materials and their applications. The wound healing applications of GO-based materials is extensively discussed with cancer therapy and drug delivery.

Berezinskii-Kosterlitz-Thouless transition in an Al superconducting nanofilm grown on GaAs by molecular beam epitaxy.

We have performed extensive transport experiments on a 4 nm thick aluminum (Al) superconducting film grown on a GaAs substrate by molecular beam epitaxy (MBE). Nonlinear current-voltage (I-V) measurements on such a MBE-grown superconducting nanofilm show that V âˆ¼ I 3, which is evidence for the Berezinskii-Kosterlitz-Thouless (BKT) transition, both in the low-voltage (T BKT ≈ 1.97 K) and high-voltage regions (T BKT ≈ 2.17 K). In order to further study the two regions where the I-V curves are BKT-like, our experimental data are fitted to the temperature-induced vortices/antivortices unbinding model as well as the dynamical scaling theory. It is found that the transition temperature obtained in the high-voltage region is the correct T BKT as confirmed by fitting the data to the aforementioned models. Our experimental results unequivocally show that I-V measurements alone may not allow one to determine T BKT for superconducting transition. Therefore, one should try to fit one's results to the temperature-induced vortices/antivortices unbinding model and the dynamical scaling theory to accurately determine T BKT in a two-dimensional superconductor.

Analysing quantized resistance behaviour in graphene Corbino p-n junction devices.

Just a few of the promising applications of graphene Corbino pnJ devices include two-dimensional Dirac fermion microscopes, custom programmable quantized resistors, and mesoscopic valley filters. In some cases, device scalability is crucial, as seen in fields like resistance metrology, where graphene devices are required to accommodate currents of the order 100 µA to be compatible with existing infrastructure. However, fabrication of these devices still poses many difficulties. In this work, unusual quantized resistances are observed in epitaxial graphene Corbino p-n junction devices held at the ν = 2 plateau (R H ≈ 12906 Ω) and agree with numerical simulations performed with the LTspice circuit simulator. The formulae describing experimental and simulated data are empirically derived for generalized placement of up to three current terminals and accurately reflects observed partial edge channel cancellation. These results support the use of ultraviolet lithography as a way to scale up graphene-based devices with suitably narrow junctions that could be applied in a variety of subfields.

Development of gateless quantum Hall checkerboard p-n junction devices.

Measurements of fractional multiples of the ν = 2 plateau quantized Hall resistance (R H ≈ 12906 Ω) were enabled by the utilization of multiple current terminals on millimetre-scale graphene p-n junction devices fabricated with interfaces along both lateral directions. These quantum Hall resistance checkerboard devices have been demonstrated to match quantized resistance outputs numerically calculated with the LTspice circuit simulator. From the devices' functionality, more complex embodiments of the quantum Hall resistance checkerboard were simulated to highlight the parameter space within which these devices could operate. Moreover, these measurements suggest that the scalability of p-n junction fabrication on millimetre or centimetre scales is feasible with regards to graphene device manufacturing by using the far more efficient process of standard ultraviolet lithography.

Implementation of a graphene quantum Hall Kelvin bridge-on-a-chip for resistance calibrations.

The unique properties of the quantum Hall effect allow one to revisit traditional measurement circuits with a new flavour. In this paper we present the first realization of a quantum Hall Kelvin bridge for the calibration of standard resistors directly against the quantum Hall resistance. The bridge design is particularly simple and requires a minimal number of instruments. The implementation here proposed is based on the bridge-on-a-chip, an integrated circuit composed of three graphene quantum Hall elements and superconducting wiring. The accuracy achieved in the calibration of a 12 906Ω standard resistor is of a few parts in 108, at present mainly limited by the prototype device and the interferences in the current implementation, with the potential to achieve few parts in 109, which is the level of the systematic uncertainty of the quantum Hall Kelvin bridge itself.

Protaetia brevitarsis seulensis Derived Protein Isolate with Enhanced Osteomodulatory and Antioxidative Property.

The osteogenic differentiation of stem cells is profoundly affected by their microenvironmental conditions. The differentiation behavior of stem cells can be tuned by changing the niche environments. The proteins or peptides that are derived by living organisms facilitate the osteogenic differentiation of stem cells. Here, we have evaluated the osteoinductive and antioxidative potential of the Protaetia brevitarsis seulensis insect-derived protein for human bone marrow-derived mesenchymal stem cells (hBMSCs). The amino acid contents in the isolated protein were determined by an amino acid analyzer. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to analyze the extract's functional groups and surface morphology. The extracted protein exhibited 51.08% ß-sheet conformation. No adverse effects were observed in extract-treated cells, indicating their biocompatibility. The protein isolate showed an excellent antioxidative property. Besides this, an enhancement in the hBMSCs' mineralization has been observed in the presence of treated protein isolates. Notably, osteogenic marker genes and proteins were effectively expressed in the treated cells. These results indicated that the P. brevitarsis-derived protein isolate can be used as a potential antioxidative biomaterial for bone tissue engineering applications.

Analytical determination of atypical quantized resistances in graphene p-n junctions.

A mathematical approach is introduced for predicting quantized resistances in graphene p-n junction devices that utilize more than a single entry and exit point for electron flow. Depending on the configuration of an arbitrary number of terminals, electrical measurements yield nonconventional, fractional multiples of the typical quantized Hall resistance at the v = 2 plateau (R H ≈ 12906 Ω) and take the form: a b R H . This theoretical formulation is independent of material, and applications to other material systems that exhibit quantum Hall behaviors are to be expected. Furthermore, this formulation is supported with experimental data from graphene devices with multiple source and drain terminals.

Superconducting Contact Geometries for Next-Generation Quantized Hall Resistance Standards.

Precision quantum Hall resistance measurements can be greatly improved when implementing new electrical contact geometries made from superconducting NbTiN. The sample designs described here minimize undesired resistances at contacts and interconnections, enabling further enhancement of device size and complexity when pursuing next-generation quantized Hall resistance devices.

Two-Terminal and Multi-Terminal Designs for Next-Generation Quantized Hall Resistance Standards: Contact Material and Geometry.

In this paper, we show that quantum Hall resistance measurements using two terminals may be as precise as four-terminal measurements when applying superconducting split contacts. The described sample designs eliminate resistance contributions of terminals and contacts such that the size and complexity of next-generation quantized Hall resistance devices can be significantly improved.

Intrinsically Multistable Soft Actuator Driven by Mixed-Mode Snap-Through Instabilities.

Actuators utilizing snap-through instabilities are widely investigated for high-performance fast actuators and shape reconfigurable structures owing to their rapid response and limited reliance on continuous energy input. However, prevailing approaches typically involve a combination of multiple bistable actuator units and achieving multistability within a single actuator unit still remains an open challenge. Here, a soft actuator is presented that uses shape memory alloy (SMA) and mixed-mode elastic instabilities to achieve intrinsically multistable shape reconfiguration. The multistable actuator unit consists of six stable states, including two pure bending states and four bend-twist states. The actuator is composed of a pre-stretched elastic membrane placed between two elastomeric frames embedded with SMA coils. By controlling the sequence and duration of SMA activation, the actuator is capable of rapid transition between all six stable states within hundreds of milliseconds. Principles of energy minimization are used to identify actuation sequences for various types of stable state transitions. Bending and twisting angles corresponding to various prestretch ratios are recorded based on parameterizations of the actuator's geometry. To demonstrate its application in practical conditions, the multistable actuator is used to perform visual inspection in a confined space, light source tracking during photovoltaic energy harvesting, and agile crawling.

Nanocellulose-assisted mechanically tough hydrogel platforms for sustained drug delivery.

The controlled delivery of the desired bioactive molecules is required to achieve the maximum therapeutic effects with minimum side effects. Biopolymer-based hydrogels are ideal platforms for delivering the desired molecules owing to their superior biocompatibility, biodegradability, and low-immune response. However, the prolonged delivery of the drugs through biopolymer-based hydrogels is restricted due to their weak mechanical stability. We developed mechanically tough and biocompatible hydrogels to address these limitations using carboxymethyl chitosan, sodium alginate, and nanocellulose for sustained drug delivery. The hydrogels were cross-linked through calcium ions to enhance their mechanical strength. Nanocellulose-added hydrogels exhibited improved mechanical strength (Young's modulus; 23.36 â†’ 30.7 kPa, Toughness; 1.39 â†’ 5.65 MJm-3) than pure hydrogels. The composite hydrogels demonstrated increased recovery potential (66.9 â†’ 84.5 %) due to the rapid reformation of damaged polymeric networks. The hydrogels were stable in an aqueous medium and demonstrated reduced swelling potential. The hydrogels have no adverse effects on embryonic murine fibroblast (3 T3), showing their biocompatibility. No bacterial growth was observed in hydrogels-treated groups, indicating their antibacterial characteristics. The sustained drug released was observed from nanocellulose-assisted hydrogel scaffolds compared to the pure polymer hydrogel scaffold. Thus, hydrogels have potential and could be used as a sustained drug carrier.

Unzipped carbon nanotubes assisted 3D printable functionalized chitosan hydrogels for strain sensing applications.

Developing multifunctional hydrogels for wearable strain sensors has received significant attention due to their diverse applications, including human motion detection, personalized healthcare, soft robotics, and human-machine interfaces. However, integrating the required characteristics into one component remains challenging. To overcome these limitations, we synthesized multifunctional hydrogels using carboxymethyl chitosan (CMCS) and unzipped carbon nanotubes (f-CNTs) as strain sensor via a one-pot strategy. The polar groups in CMCS and f-CNTs enhance the properties of the hydrogels through different interactions. The hydrogels show superior printability with a uniformity factor (U) of 0.996 ± 0.049, close to 1. The f-CNTs-assisted hydrogels showed improved storage modulus (8.8 × 105 Pa) than the pure polymer hydrogel. The hydrogels adequately adhered to different surfaces, including human skin, plastic, plastic/glass interfaces, and printed polymers. The hydrogels demonstrated rapid self-healing and good conductivity. The biocompatibility of the hydrogels was assessed using human fibroblast cells. No adverse effects were observed with hydrogels, showing their biocompatibility. Furthermore, hydrogels exhibited antibacterial potential against Escherichia coli. The developed hydrogel exhibited unidirectional motion and complex letter recognition potential with a strain sensitivity of 2.4 at 210 % strain. The developed hydrogels could explore developing wearable electronic devices for detecting human motion.

A Method for 3D Printing and Rapid Prototyping of Fieldable Untethered Soft Robots.

Because they are made of elastically deformable and compliant materials, soft robots can passively change shape and conform to their environment, providing potential advantages over traditional robotics approaches. However, existing manufacturing workflows are often labor intensive and limited in their ability to create highly integrated three-dimensional (3D) heterogeneous material systems. In this study, we address this with a streamlined workflow to produce field-deployable soft robots based on 3D printing with digital light processing (DLP) of silicone-like soft materials. DLP-based 3D printing is used to create soft actuators (2.2 g) capable of exerting up to 0.5 Newtons of force that are integrated into a bioinspired untethered soft robot. The robot walks underwater at speeds comparable with its biological analog, the brittle star. Using a model-free planning algorithm and feedback, the robot follows remote commands to move to desired positions. Moreover, we show that the robot is able to perform untethered locomotion outside of a laboratory and in a natural aquatic environment. Our results represent progress in soft robot manufacturing autonomy for a 3D printed untethered soft robot.

Soft magnetic thin film deformation with a bistable electropermanent magnet.

Physically soft magnetic materials (PSMMs) represent an emerging class of materials that can change shape or rheology in response to an external magnetic field. However, until now, no studies have investigated using an electropermanent magnet (EPM) and magnetic repulsion to magnetically deform PSMMs. Such capabilities would enable the ability to deform PSMMs without the need for continuous electrical input and produce PSMM film deformation without an air gap, as would be required with magnetic attraction. To address this, we introduce a PSMM-EPM architecture in which the shape of a soft deformable thin film is controlled by switching between bistable on/off states of the EPM circuit. We characterized the deflection of a PSMM thin film when placed at controlled distances normal to the surface of the EPM and compared its response for cases when the EPM is in the 'on' and 'off' states. This work is the first to demonstrate a magnetically repelled soft deformable thin film that achieves two electronically-controlled modes of deformation through the on and off states of an EPM. This work has the potential to advance the development of new magneto-responsive soft materials and systems.

Electrically stimulated 3D bioprinting of gelatin-polypyrrole hydrogel with dynamic semi-IPN network induces osteogenesis via collective signaling and immunopolarization.

In recent years, three-dimensional (3D) bioprinting of conductive hydrogels has made significant progress in the fabrication of high-resolution biomimetic structures with gradual complexity. However, the lack of an effective cross-linking strategy, ideal shear-thinning, appropriate yield strength, and higher print fidelity with excellent biofunctionality remains a challenge for developing cell-laden constructs, hindering the progress of extrusion-based 3D printing of conductive polymers. In this study, a highly stable and conductive bioink was developed based on polypyrrole-grafted gelatin methacryloyl (GelMA-PPy) with a triple cross-linking (thermo-photo-ionically) strategy for direct ink writing-based 3D printing applications. The triple-cross-linked hydrogel with dynamic semi-inner penetrating polymer network (semi-IPN) displayed excellent shear-thinning properties, with improved shape fidelity and structural stability during 3D printing. The as-fabricated hydrogel ink also exhibited "plug-like non-Newtonian" flow behavior with minimal disturbance. The bioprinted GelMA-PPy-Fe hydrogel showed higher cytocompatibility (93%) of human bone mesenchymal stem cells (hBMSCs) under microcurrent stimulation (250 mV/20 min/day). Moreover, the self-supporting and tunable mechanical properties of the GelMA-PPy bioink allowed 3D printing of high-resolution biological architectures. As a proof of concept, we printed a full-thickness rat bone model to demonstrate the structural stability. Transcriptomic analysis revealed that the 3D bioprinted hBMSCs highly expressed gene hallmarks for NOTCH/mitogen-activated protein kinase (MAPK)/SMAD signaling while down-regulating the Wnt/ß-Catenin and epigenetic signaling pathways during osteogenic differentiation for up to 7 days. These results suggest that the developed GelMA-PPy bioink is highly stable and non-toxic to hBMSCs and can serve as a promising platform for bone tissue engineering applications.