We combined reflection difference microscopy, electron transport measurements, and atomic force microscopy to characterize the mechanical and electrical anisotropy of few-layer black phosphorus. We were able to identify the lattice orientations of the two-dimensional material and construct suspended structures aligned with specific crystal axes. The approach allowed us to probe the anisotropic mechanical and electrical properties along each lattice axis in separate measurements. We measured the Young's modulus of few-layer black phosphorus to be 58.6 ± 11.7 and 27.2 ± 4.1 GPa in zigzag and armchair directions. The breaking stress scaled almost linearly with the Young's modulus and was measured to be 4.79 ± 1.43 and 2.31 ± 0.71 GPa in the two directions. We have also observed highly anisotropic transport behavior in black phosphorus and derived the conductance anisotropy to be 63.7%. The test results agreed well with theoretical predictions. Our work provided very valuable experimental data and suggested an effective characterization means for future studies on black phosphorus and anisotropic two-dimensional nanomaterials in general.

Polarized photodetectors with wide spectral detection and ultra‐fast photoresponses based on anisotropic semiconductors have potential applications in military and civilian fields and have been widely studied in recent years. The dual advantages of low‐symmetry crystal structure and special electronic band‐structure make Sb2S3 the perfect choice for polarized photodetection. In this work, the optical, vibrational, and optoelectronic anisotropy of the high‐quality orthorhombic Sb2S3 nanowires are systematically investigated by experimental and theoretical studies. The metal‐semiconductor‐metal photodetectors based on a single Sb2S3 nanowire exhibit good polarization sensitivity in a broadband range from ultraviolet to near‐infrared (360 to 1550 nm) and the obtained maximum dichroic ratio is 2.54 at 638 nm. The polarization‐sensitive photocurrent mapping results show that the photocurrent is mainly derived from the Schottky junction at the interface between Au and Sb2S3. The effective separation of the photo‐generated carriers near the Schottky junction gives a photodetector response time of 470 µs. The direct polarimetric imaging demonstrates that the gray value of the image obtained by the imaging system is sensitive to the object's polarized direction. This natural sensitivity of the Sb2S3‐based photodetector to polarized objects makes it possible to image polarized objects directly as an image sensor.

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We demonstrate an optical method to realize controllable formation and precise manipulation of microdroplet using optical tweezers (OT). With the irradiation of a highly focused laser into the mixture of inorganic phosphate buffered saline (PBS) and organic solvent isopropanol, a microdroplet was gradually formed at the center of the trap. The size and the growth rate of the microdroplet could be precisely controlled by regulating the laser power and the proportion of two solvents in the mixture. Furthermore, the microdroplet could be manipulated by OT to build microstructures on the slide. We also discuss the possible mechanism behind our observations and the potential usage of such discoveries.

Single-molecule atomic force spectroscopy (AFM) has evolved into a powerful technique toward elucidating conformational changes in proteins when exposed to applied force. AFM technologies that are currently available allow for precise measurements of proteins length changes during conformational transitions. However, because of systematic errors in piezo calibration as well as errors originating from fitting experimental data using a worm-like chain model of polymer elasticity, high-precision measurements of length changes do not necessarily translate into highly accurate measurements of length changes, resulting in uncertainty in obtaining structural information about protein conformational changes. Actually achieving highly precise and accurate force spectroscopy measurements remains a challenge. Here, we report a protein caliper method that eliminates systematic errors that occur during single-protein force spectroscopy measurements, and thus achieves highly precise and accurate length change measurements in protein mechanics studies. To do this, a series of loop elongation variants of the small protein GB1, which differ by 2, 5, 10, 15, and 24 amino acid residues, were engineered. Differential measurements of amino acid residue length obtained from different AFM setups result in a precise measure of the length of a single amino acid residue, which varies within different AFM setups because of systematic error between individual AFM piezoelectric calibrations. The measured length of a single amino acid residue from a given AFM setup is then used as a caliper for the given setup to eliminate systematic error, leading to highly accurate and precise measurements of the number of amino acid residues that are involved in a conformation change of a polypeptide chain. We further developed a more precise, robust, and model-free method to determine the apparent size of single amino acid residues and conformational changes of proteins. This method improves the accuracy of single protein force spectroscopy measurements, providing an accurate means of measuring force-induced protein conformational changes.