Quantitative Phase Imaging Camera With a Weak Diffuser

We introduce the quantitative phase imaging camera with a weak diffuser (QPICWD) as an effective scheme of quantitative phase imaging (QPI) based on normal microscope platforms. The QPICWD is an independent compact camera measuring object induced phase delay under low-coherence quasi-monochromatic illumination by examining the deformation of the speckle intensity pattern. By interpreting the speckle deformation with an ensemble average of the geometric flow, we can obtain the high-resolution distortion field via the transport of intensity equation (TIE). Since the phase measured by TIE is the generalized phase of the partially coherent image, rather than the phase of the measured object, we analyze the effect of illumination coherence and imaging numerical aperture (NA) on the accuracy of phase retrieval, revealing that the sample's phase can be reliably reconstructed under the conditions that the coherence parameter (the ratio of illumination NA to objective NA) of the Köhler illumination is between 0.3 and 0.5. We present some applications for the proposed design involving nondestructive optical testing of microlens array with nanometric thickness and imaging of fixed and live unstained HeLa cells. Since the designed QPI camera does not require any modification of the widely available bright-field microscope or additional accessories for its use, it is expected to be applied by the broader communities of biology and medicine

NanoFe3O4 as Solid Electron Shuttles to Accelerate Acetotrophic Methanogenesis by Methanosarcina barkeri

Magnetite nanoparticles (nanoFe3O4) have been reported to facilitate direct interspecies electron transfer (DIET) between syntrophic bacteria and methanogens thereby improving syntrophic methanogenesis. However, whether or how nanoFe3O4 affects acetotrophic methanogenesis remain unknown. Herein, we demonstrate the unique role of nanoFe3O4 in accelerating methane production from direct acetotrophic methanogenesis in Methanosarcina-enriched cultures, which was further confirmed by pure cultures of Methanosarcina barkeri. Compared with other nanomaterials of higher electrical conductivity such as carbon nanotubes and graphite, nanoFe3O4 with mixed valence Fe(II) and Fe(III) had the most significant stimulatory effect on methane production, suggesting its redox activity rather than electrical conductivity led to enhanced methanogenesis by M. barkeri. Cell morphology and spectroscopy analysis revealed that nanoFe3O4 penetrated into the cell membrane and cytoplasm of M. barkeri. These results provide the unprecedented possibility that nanoFe3O4 in the cell membrane of methanogens serve as electron shuttles to facilitate intracellular electron transfer and thus enhance methane production. This work has important implications not only for understanding the mechanisms of mineral-methanogen interaction but also for optimizing engineered methanogenic processes

Highly stretchable conductor inspired by compliant mechanism

Flexible and stretchable conductors have invaluable applications in multiple domains, such as sensors, displays, and electronic skins. The stable conductance exhibited by conductors when subjected to diverse forms of deformation, such as tensile stress, curvature, or torsion, represents a fundamental characteristic. Attaining high conductivity and stretchability simultaneously in conductive materials is a formidable challenge, owing to inherent constraints in materials found in nature. To overcome this problem, an innovative approach of structurally designing conductors using existing materials to achieve high deformability and stretchability, i.e. stretchable conductors inspired by a compliant mechanism is proposed in this paper. Thus, a novel stretchable conductor inspired by flexible mechanisms is introduced. Unlike stretchable conductors based on Kirigami structures, the stretchable conductor based on flexible mechanisms can achieve large in‐plane deformation within the material's strength limit. The concept and design process of the highly deformable stretchable conductor inspired by flexible mechanisms are presented in this paper. Experimental results show that the resistance change ratio of the conductor remains within 0.05% during the 0–200% strain process. The consistency and durability of the conductor during stretching deformation are also confirmed through 500 repetitions of the test. Additionally, the experiments with the electric motor and light‐emitting diode (LED) light confirm the conductor's ability to maintain a stable current

Autofocusing Algorithm for Pixel-Super-Resolved Lensfree On-Chip Microscopy

In recent years, lensfree on-chip microscopy has developed into a promising and powerful computational optical microscopy technique that allows for wide-field, high-throughput microscopic imaging without using any lenses. However, due to the limited pixel size of the state-of-the-art image sensors, lens-free on-chip microscopy generally suffers from low imaging resolution, which is far from enough to meet the current demand for high-resolution microscopy. Many pixel super-resolution techniques have been developed to solve or at least partially solve this problem by acquiring a series of low-resolution holograms with multiple lateral sub-pixel shifting or axial distances. However, the prerequisite of these pixel super-resolution techniques is that the propagation distance of each low-resolution hologram can be obtained precisely, which faces two major challenges. On the one hand, the captured hologram is inherent pixelated and of low resolution, making it difficult to determine the focal plane by evaluating the image sharpness accurately. On the other hand, the twin-image is superimposed on the backpropagated raw hologram, further exacerbating the difficulties in accurate focal plane determination. In this study, we proposed a high-precision autofocusing algorithm for multi-height pixel-super-resolved lensfree on-chip microscopy. Our approach consists of two major steps: individual preliminary estimation and global precise estimation. First, an improved critical function that combines differential critical function and frequency domain critical function is proposed to obtain the preliminary focus distances of different holograms. Then, the precise focus distances can be determined by further evaluating the global offset of the averaged, low-noise reconstruction from all backpropagated holograms with preliminary focus distances. Simulations and experimental results verified the validity and effectiveness of the proposed algorithm.</jats:p