Use of Digital Image Correlation Method to Measure Bio-Tissue Deformation

An Acoustic Device for Ultra High-Speed Quantification of Cell Strain During Cell-Microbubble Interaction

Microbubbles utilize high-frequency oscillations under ultrasound stimulation to induce a range of therapeutic effects in cells, often through mechanical stimulation and permeabilization of cells. One of the largest challenges remaining in the field is the characterization of interactions between cells and microbubbles at therapeutically relevant frequencies. Technical limitations, such as employing sufficient frame rates and obtaining sufficient image resolution, restrict the quantification of the cell's mechanical response to oscillating microbubbles. Here, a novel methodology was developed to address many of these limitations and improve the image resolution of cell-microbubble interactions at high frame rates. A compact acoustic device was designed to house cells and microbubbles as well as a therapeutically relevant acoustic field while being compatible with a Shimadzu HPV-X camera. Cell viability tests confirmed the successful culture and proliferation of cells, and the attachment of DSPC- and cationic DSEPC-microbubbles to osteosarcoma cells was quantified. Microbubble oscillation was observed within the device at a frame rate of 5 million FPS, confirming suitable acoustic field generation and ultra high-speed image capture. High spatial resolution in these images revealed observable deformation in cells following microbubble oscillation and supported the first use of digital image correlation for strain quantification in a single cell. The novel acoustic device provided a simple, effective method for improving the spatial resolution of cell-microbubble interaction images, presenting the opportunity to develop an understanding of the mechanisms driving the therapeutic effects of oscillating microbubbles upon ultrasound exposure.

Mechanical Property Test of Grass Carp Skin Material Based on the Digital Image Correlation Method

Fish is a common and widely distributed creature. Its skin has a unique physiological structure and plays an important role in many fields. Fish skin also has important potential value for bionics research. This study aims to provide a method and a reliable data for the study of bionics. A method of measuring the mechanical properties of fish skin samples using a binocular stereo digital image correlation (DIC) system combined with a synchronous tensile testing machine was proposed. The mechanical properties (e.g., elastic modulus E and strain) of grass fish skin samples (GFSA) were tested in hydrophilic and dry states. A dual-frequency laser interferometer was used to calibrate the tensile testing machine synchronously, and the feasibility and strain accuracy of DIC in GFSA measurement were verified by finite element method (FEM). The results show differences in the mechanical properties of GFSA between different individuals, different parts, and different states. Under the same stress, the head was easy to deform, and the strain was the largest, and E was the smallest. The tail result was the opposite of the head result.

Mechanical Properties and Residual Stress Measurement of TiN/Ti Duplex Coating Using HiPIMS TiN on Cold Spray Ti

This study investigated the mechanical properties and the residual stress of high-power impulse magnetron sputtering (HiPIMS) titanium nitride (TiN) thin film capping on cold spray titanium (Ti) coating. This TiN/Ti duplex coating was deposited on the Ti substrate, and the cold spray titanium (Ti) coating was prepared in three cases with different numbers of layers. The study determined Young’s modulus, hardness, and roughness of TiN thin film and cold spray Ti coatings by nano-indentation and AFM. The residual stress measurement of TiN/Ti duplex coating was conducted using the ring-core drilling method. A focused ion beam (FIB) drilled the TiN/Ti duplex coating with various milling depth steps. The corresponding images were obtained with a scanning electron microscope (SEM). The relationship between surface deformations and relaxation stress after each milling depth step was obtained using the digital image correlation (DIC) method. The results showed TiN/Ti duplex coating exhibited excellent mechanical properties, and the residual stresses were not significantly changing with different Ti cold spray substrates, showing the feasibility of coating technology for the future applications in the aerospace industry.