Piezoelectrically actuated four-bar mechanism with two flexible links for micromechanical flying insect thorax

In this paper, a piezoelectrically actuated four-bar mechanism with two flexible links is proposed to be used in a micromechanical flying insect robot wing thorax for stroke amplification. PZT-5H- and PZN-PT-based unimorph actuators are utilized at the input link of the four-bar for a compact and lightweight thorax transmission mechanism. The kinematics and dynamics of the proposed wing structure with two parallel four-bar mechanisms are analyzed, optimal four-bar link size selection method is introduced, and quasistatic forces generated at the wing are computed for evaluating the feasibility of the design. Using laser micromachining and folding techniques, prototype four-bar structures are constructed. In the experiments, for a 10/spl times/1/spl times/0.12 mm/sup 3/ PZT-5H actuator-based four-bar mechanism, the stroke amplification of around 20 - 25 is held, and an attached polyester wing is resonated at 29 Hz with around 90/spl deg/ flapping motion. These results match closely with the predicted theoretical values.     

Bio‐Hybrid Cell‐Based Actuators for Microsystems

As we move towards the miniaturization of devices to perform tasks at the nano and microscale, it has become increasingly important to develop new methods for actuation, sensing, and control. Over the past decade, bio‐hybrid methods have been investigated as a promising new approach to overcome the challenges of scaling down robotic and other functional devices. These methods integrate biological cells with artificial components and therefore, can take advantage of the intrinsic actuation and sensing functionalities of biological cells. Here, the recent advancements in bio‐hybrid actuation are reviewed, and the challenges associated with the design, fabrication, and control of bio‐hybrid microsystems are discussed. As a case study, focus is put on the development of bacteria‐driven microswimmers, which has been investigated as a targeted drug delivery carrier. Finally, a future outlook for the development of these systems is provided. The continued integration of biological and artificial components is envisioned to enable the performance of tasks at a smaller and smaller scale in the future, leading to the parallel and distributed operation of functional systems at the microscale.     

3D Microstructures of Liquid Crystal Networks with Programmed Voxelated Director Fields

The shape-shifting behavior of liquid crystal networks (LCNs) and elastomers (LCEs) is a result of an interplay between their initial geometrical shape and their molecular alignment. For years, reliance on either one-step in situ or two-step film processing techniques has limited the shape-change transformations from 2D to 3D geometries. The combination of various fabrication techniques, alignment methods, and chemical formulations developed in recent years has introduced new opportunities to achieve 3D-to-3D shape-transformations in large scales, albeit the precise control of local molecular alignment in microscale 3D constructs remains a challenge. Here, the voxel-by-voxel encoding of nematic alignment in 3D microstructures of LCNs produced by two-photon polymerization using high-resolution topographical features is demonstrated. 3D LCN microstructures (suspended films, coils, and rings) with designable 2D and 3D director fields with a resolution of 5 µm are achieved. Different shape transformations of LCN microstructures with the same geometry but dissimilar molecular alignments upon actuation are elicited. This strategy offers higher freedom in the shape-change programming of 3D LCN microstructures and expands their applicability in emerging technologies, such as small-scale soft robots and devices and responsive surfaces.     

Influence of leather meal fertilizer on soil organic matter: A laboratory study

Leather meal fertilizer was mixed with a soil (Typic Xerorthent) and incubated in the laboratory for one year at room temperature. Soil samples were collected periodically and analyzed in order to follow the transformation of the organic matter as well as the availability of Cr and certain plant nutrients.The results obtained showed intense mineralization during the first 60–120 days of the incubation period. The amount of humic acids (HAs) separated from the alkaline extracts showed that the humification level increased markedly after the first 60 days of incubation and, as shown by IEF analysis, organic compounds similar to the soil humic substances were formed.Variations in the amount of available nutrients were observed; only the extractable Cr increased during the first period of mineralization.     

Identification of blood meal in fertilizers

A simple and useful analytical method is proposed for the characterization of blood meal fertilizer, a quality organic fertilizer commonly used in agriculture. Despite the agronomical and commercial importance of this organic fertilizer, Italian law does not indicate an analytical method for its identification in organic matrices. This situation is very unsatisfactory because unscrupulous producers could declare the presence of a quality organic fertilizer, such as blood meal, instead of a poorer fertilizer. In this work the heme group of the hemoglobin contained in blood meal was characterized spectrophotometrically and a calibration curve prepared using different concentrations of hemoglobin was used to determine the hemoglobin content in six blood meal samples. The method was successfully applied for the qualitative identification of hemoglobin in mixtures of organic and/or organic fertilizers with small amounts (3–10%) of blood meal.     

Biohybrid Microtube Swimmers Driven by Single Captured Bacteria

Bacteria biohybrids employ the motility and power of swimming bacteria to carry and maneuver microscale particles. They have the potential to perform microdrug and cargo delivery in vivo, but have been limited by poor design, reduced swimming capabilities, and impeded functionality. To address these challenge, motile Escherichia coli are captured inside electropolymerized microtubes, exhibiting the first report of a bacteria microswimmer that does not utilize a spherical particle chassis. Single bacterium becomes partially trapped within the tube and becomes a bioengine to push the microtube though biological media. Microtubes are modified with “smart” material properties for motion control, including a bacteria‐attractant polydopamine inner layer, addition of magnetic components for external guidance, and a biochemical kill trigger to cease bacterium swimming on demand. Swimming dynamics of the bacteria biohybrid are quantified by comparing “length of protrusion” of bacteria from the microtubes with respect to changes in angular autocorrelation and swimmer mean squared displacement. The multifunctional microtubular swimmers present a new generation of biocompatible micromotors toward future microbiorobots and minimally invasive medical applications.