Highly Sensitive Flexible Modulus Sensor for Softness Perception and Clinical Application

The wearable sensors for softness measuring are emerging as a solution of softness perception, which is an intrinsic function of human skin, for electronic skin and human-machine interaction. However, these wearable sensors suffer from a key challenge: the modulus of an object can not be characterized directly, which originates from the complicated transduction mechanism. To address this key challenge, we developed a flexible and wearable modulus sensor that can simultaneously measure the pressure and modulus without mutual interference. The modulus sensing was realized by merging the electrostatic capacitance response from the pressure sensor and the ionic capacitance response from the indentation sensor. Via the optimized structure, our sensor exhibits high modulus sensitivity of 1.9 × 102 in 0.06 MPa, a fast dynamic response time of 100 ms, and high mechanical robustness for over 2500 cycles. We also integrated the sensor onto a prosthetic hand and surgical probe to demonstrate its capability for pressure and modulus sensing. This work provides a new strategy for modulus measurement, which has great potential in softness sensing and medical application.

The E-modulus of the oocyte is a non-destructive measure of zona pellucida hardening

After fertilization, the oocyte-specific metalloproteinase ovastacin is released and cleaves the zona pellucida protein 2 (ZP2), making the zona pellucida impermeable to sperm. Before fertilization, the zona remains permeable because previously released ovastacin is inhibited by fetuin-B. Consequently, in the absence of fetuin-B, ZP2 cleavage occurs prematurely and leads to infertility of female fetuin-B deficient mice. In contrast, fetuin-B/ovastacin double-deficient oocytes show a permanently permeable zona with intact ZP2. In this study, we asked if the elastic modulus of the zona pellucida informs about ZP2 cleavage and thus could serve as a new reference of oocyte fertility. Therefore, we determined the elastic modulus of mouse oocytes by nanoindentation as a direct measure of mechanical zona hardening. The elastic modulus reflects ZP2 cleavage, but with more than double sensitivity compared to immunoblot analysis. The elastic modulus measurement allowed to define the range of zona hardening, confined by the extreme states of the zona pellucida in fetuin-B and ovastacin-deficient oocytes with cleaved and uncleaved ZP2, respectively. We present here nanoindentation as a method to quantify the effect of potential contributing factors on the zona hardening of individual oocytes. To demonstrate this, we showed that mechanical hardening of the zona pellucida is forced by recombinant ovastacin, inhibited by additional administration of fetuin-B, and unaffected by zinc. Since the change in elastic modulus is induced by ZP2 cleavage, an automated elastic modulus measurement of oocytes may serve as a novel sensitive, non-destructive, marker-free, and observer-unbiased method for assessing individual oocyte quality.

In Situ Measurement of Elastic and Frictional Properties Using Atomic Force Microscopy

Atomic force microscopy (AFM) can determine mechanical properties, associated with surface topography and structure, of a material at the nanoscale. Force–indentation curves that depict the deformation of a target specimen as a function of an applied force are widely used to determine the elastic modulus of a material based on a contact model. However, a hysteresis may arise due to friction between the AFM tip and a specimen. Consequently, the normal force detected using a photodetector during extension and retraction could be underestimated and overestimated, respectively, and the extension/retraction data could result in a significant difference in the elastic modulus measurement result. In this study, elastic modulus and friction coefficient values were determined based on an in situ theoretical model that compensated for the effect of friction on force–indentation data. It validated the proposed model using three different polymer specimens and colloidal-tipped probes for the force–indentation curve and friction loop measurements. This research could contribute to the accurate measurement of mechanical properties using AFM by enhancing the interpretation of force–indentation curves with friction-induced hysteresis. Furthermore, the proposed approach may be useful for analyzing in situ relationships between mechanical and frictional properties from a fundamental tribological perspective.

Pengukuran Modulus Geser Baja Menggunakan Analisis Osilasi Pegas-Massa

A steel shear modulus measurement has been conducted using spring-mass oscillation analysis. The purpose of this study is to determine whether the spring-mass oscillation analysis method can measure the shear modulus of the steel. In this study, springs that are used are made of steel with a spring radius of 7.86 mm, a spring wire diameter of 0.817 mm and there is no distance between the coil springs. The length of the spring is varied 7 times, i.e., 4.75 cm, 5.36 cm, 5.89 cm, 6.81 cm, 8.53 cm, 9.44 cm, and 10.87 cm. The spring radius and the diameter of the spring wire are measured using a micrometer screw, while the spring length is determined using image analysis using the Logger Pro program. The spring constant is determined from the equation of the results of the position graph fitting (x) with respect to time (t) load on the oscillating spring-mass system. The value of the shear modulus can be determined from the constants on the graph of the relationship of the spring constant to the spring length following the equation from Sommerfeld. The research measures the shear modulus is 1.24 GPa