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Quadcopters can play an important role in precision agriculture; mostly having been researched and commercialized for the open field conditions. While greenhouse applications have been limited by the positioning system. Conventional GPS positioning systems are difficult to use in greenhouses. Spread Spectrum Sound-based Positioning System (SSSPS) on the other hand, has the potential to be used on a quadcopter in a greenhouse. In this research, we evaluated whether acoustic noise from a quadcopter over wide frequency range would interfere with the SSSPS operation. We set a microphone on the quadcopter, and evaluated the SSSPS system for quadcopter noise tolerance with several signals. The results demonstrate the navigation system can tolerate quadcopter noise over distances up to 15 m between the tweeter and the microphone on the quadcopter with the RMSE of 5.9 mm.

Traditional greenhouse robots are heavy and expensive, so a small size with low cost platform is needed. When operating small distributed robots in a greenhouse, a positioning and orientation system will be needed for the accurate control. While the traditional methods of determining orientation have limited application in greenhouses due to the errors associated with indoor GPS compasses or the sensitivity of magnetic direction sensors to magnetic materials in the greenhouse. In this research, we develop methods for determining orientation using a sound signal and two receivers. These methods were then experimentally evaluated in a greenhouse with and without manually removing distance reflection data. After deleting these signal reflection errors, the average accuracy of the two methods was determined to be 3.1° and 2.8°, respectively.

Circulating extracellular vesicles (EVs) are considered as potential biomarkers for treatment and diagnosis of many diseases. Most of the existing methods for the EV analysis only have a single function and thus reveal limited information carried by EVs. Herein, a phosphatidylserine‐targeting peptide‐facilitated design that enables the versatile analysis of circulating EVs for varying requirement is proposed. In the design, DNA probes are inserted into the EV membrane through hydrophobic interactions, and accelerate the removal of protective shielding from DNA‐gated metal–organic framework, thereby releasing a large number of methylene blue molecules to amplify the electrochemical signal. Electrochemical results demonstrate equally high sensitivities toward the quantification of EVs derived from different cell sources using an indiscriminative DNA probe. More importantly, the probe can be endowed with extended function for more accurate classification of cell‐specific features through the identification of specific EV biomarkers, and demonstrates the potential use in the diagnosis of cardiovascular in a principle‐of‐proof study for clinical application. Therefore, the method provides a versatile design for the identification of EV features, and may address the needs of clinical diagnosis in the future. A flexible and versatile design is developed for electrochemical analysis of circulating extracellular vesicles (EVs) to meet different requirements in disease diagnosis. The design not only allows to reflect the total EV level and distinguish cell‐specific EV subpopulation but also demonstrates the potential use in diagnosing acute myocardial infarction and breast cancer patients.

Multilayer van der Waals (vdW) materials exhibit nontrivial out-of-plane responses and deformability due to their inherent atomic scale thickness coupled with weak interlayer vdW interactions, which call for a general mechanical framework to quantify such extraordinary characteristics given the structure and material properties. Here, we demonstrate that by considering the competing mechanisms between intralayer stretching, interlayer shearing, and monolayer bending, a general centerline-based theory for multilayered structures is developed to portray the bending landscape of multilayer vdW materials. Combined with large-scale molecular dynamics simulations of three-point bending, we find that when the slenderness ratio or the interlayer shear rigidity is smaller or the intralayer elasticity is higher, the multilayered structures exhibit pronounced nonplanar section deformation due to the interlayer shear capacity. To elucidate quantitative correlations between deformation distribution and structural dimensions and material properties, a critical criterion is proposed to depict the transformation from planar to nonplanar section deformation through a dimensionless characteristic parameter. The effective bending stiffness is then systematically explored in the space of characteristic geometries and material properties to reveal the underlying mechanism of the anomalous size effect. We identify that the effective bending stiffness follows a unified scaling law regarding the dimensionless characteristic parameter. More importantly, a series of deformation-mode phase diagrams are constructed using two universal characteristic lengths, intuitively illustrating the transition of dominated deformation modes and the synergism of geometries and inherent material properties on the bending responses. Validated by several typical vdW materials and novel semiconducting two-dimensional materials, the proposed diagrams not only deepen the understanding of bending in multilayer vdW materials but also provide guidelines for the design and optimization of vdW material-based devices. [ABSTRACT FROM AUTHOR]