Non-contact Mode Research Articles

Anterior cruciate ligament tear due to non-contact mode of injury associated with higher incidence of meniscal and chondral damage

BackgroundForces acting on the knee are different in contact and non-contact mode of injuries causing anterior cruciate ligament (ACL) tear. Purpose of this study was to determine the effect of mode of injury on the occurrence of meniscal tear and chondral damage in ACL tear. Method72 athletes with acute ACL injury (<3 months) were enrolled in the study. Depending on the mode of injury, athletes were divided into two groups - group A (non-contact mode of injury) and group B (contact mode of injury). 49/72 athletes had the non-contact mode of injury (group A), and 23/72 athletes had contact mode of injury (group B). Meniscal tear and chondral damage seen at the time of ACL reconstruction surgery was noted. All athletes were assessed at 12 months follow-up for return to sports, Lysholm score, and WOMAC score. ResultsIn group A, 35/49 (71%) athletes and in group B, 9/23(39%) athletes had meniscal tear (p = 0.009). Medial meniscus was more commonly injured in group A [24/49] as compared to group B (5/23; p = 0.03). Chondral damage was also more commonly seen in group A [26/49] as compared to group B (5/23; p = 0.01). At one-year follow-up, 65% of the athletes from group B returned to sports as compared to 57% of the athletes from group A (p-value = 0.6). WOMAC score in group A and B was 95.5 ± 4.88 and 96 ± 4.39 respectively (p = 0.67). Lysholm score in group A and B was 1.02 ± 1.7 and 0.96 ± 1.2 respectively (p = 0.88). ConclusionNon-contact mode of injury was associated with a higher incidence of meniscal tear and chondral damage. However, the mode of injury does not affect the functional outcome of ACL reconstruction surgery.

Analysis of the atomic force microscopy vibration behavior using the Timoshenko theory by multi-scale method in the air environment.

This article deals with the modeling and simulation of the vibration behavior of piezoelectric micro-cantilever (MC) based on the Timoshenko theory and using multi-scale (MTS) method in the air environment. In this regard, the results are compared with the previous literature, such as the finite element method and the MTS method. The analysis of the piezoelectric MC vibrating behavior is investigated in a dynamical mode including non-contact and tapping modes. The dynamics of this system is affected by interferential forces between probe tip and sample surface, such as van der Waals, capillary, and contact forces. According to the results, the forces applied to the probe tip reduce the amplitude and the resonance frequency. The simulation of surface topography in non-contact mode and tapping for rectangular and wedge-shaped roughness in the air environment are presented. Various experiments have been conducted in Ara research Company using the atomic force microscopy device in the amplitude mode. In the NSC15 Cantilever, the first natural frequency is derived from the results of the MC simulation based on Timoshenko beam theory, the practical results are 295.85 and 296.12 kHz, and the error rate is 0.09; at higher natural frequencies, the error rate has been increased. The γ f coefficient is a measure of the nonlinear effects on the system; the effect of the piezoelectric length and width on γ f coefficient is also investigated.

A double‐mode cell to measure pitting and crevice corrosion

AbstractPitting corrosion and crevice corrosion of passivated steels were measured by using a double‐mode syringe electrolyte cell built on an environment chamber. The setup, when set in noncontact mode, could measure pitting potentials and critical temperatures, and crevice corrosion potentials if in contact mode. It could be employed to distinguish the pitting and crevice corrosion damage of reinforcing steel in concrete.

Sliding non-contact inductive nanogenerator

Nanogenerators generate power by inducing charge moving between the electrodes after charge generation. Using this principle, all the generated charges have the potential to design nanogenerators. In this work, we designed a new configuration that can generate power by electrostatic induction in a universally applicable way. The conversion efficiency of the contact and non-contact configuration was compared and it was found that the output capability of the non-contact inductive nanogenerator (NCING) did not decrease significantly. In addition to the traditional triboelectric non-contact mode and electret induced power generation, it was found that this configuration is applicable to more charge-induced power generation, so we directly used a charged capacitor to complete the induction power generation, which has not been reported yet. Through these experiments, we have proven the powerful ability of the free sliding non-contact configuration. In future research, the charge source can be replaced with other ones. By controlling the fixed charge to generate a higher potential, the output can be improved. Therefore, this wide-applicable generation mechanism has a huge impetus to the design of new nanogenerators.

The surgical ablation on soft tissues using Ho:YAG laser with deviated beam fiber

Abstract In this work, we demonstrate the use of 2.12-μm Ho:YAG laser with a deviated-firing fiber for laser ablation on chicken tissues. The tissue ablation tests were conducted under non-contact and contact conditions. The thermal damage and ablation efficiency made by the fiber on the tissue were quantitatively analyzed and compared. It is found that, the ablation threshold is lower and ablation is more efficient under the non-contact mode, in which the fiber device is kept at a small distance of 0.5–1.0 mm from the target tissue. This can be attributed to amber space between the fiber and the tissue that allows the ejection of ablation debris and vapor from the ablation zone. This ensures better transmission of laser energy from the fiber device to the target tissue. Such design offers better ablation efficient and enhances the service life of the medical fiber device.

A simple method for characterizing mechanical property of nanowire arrays in atmospheric environment

An unique method based on atomic force microscopy (AFM) and resonance for accurately characterizing elastic modulus of nanowire (NW) arrays in atmospheric environment is demonstrated without destructing or manipulating the sample. By acquiring the topography images of the NW arrays under frequency tunable AC electric field through AFM noncontact scanning mode, the resonance frequency of NWs can be easily identified and elastic modulus of the NW arrays is further derived. The measurement mechanism is based on quantifying the AFM tip scanning depth in the spaces of NWs to achieve the information of vibration. For the first time, the elastic modulus of ZnO NWs synthesized by of hydrothermal method is measured to be 55.7 ± 8.3 GPa.

A tip-based metrology framework for real-time process feedback of roll-to-roll fabricated nanopatterned structures

This paper presents the development of a metrology framework and proof-of-concept tool to perform direct, nanometer-scale topography measurements for real-time process control in the roll-to-roll manufacturing of nanopatterened materials, films, and flexible electronic devices. The system leverages a uniquely compact single chip atomic force microscope (sc-AFM) based on a micro-electromechanical system (MEMS) architecture with custom approach mechanism positioned on a gantry which is actuated by two vertical, double parallelogram flexure mechanism guided two-axis nanopositioners. This probe is situated over a stainless-steel, air bearing supported idler roller and its position dynamically compensated for curvature, eccentricity and surface topography of the roller during web movement through the system from an offline map. The proof-of-concept tool performs a single, 400 μm2, non-contact tapping mode scan with nm height resolution on a flexible, 150 μm × 350 mm polycarbonate substrate every 60 s in a step-and-scan fashion where web movement occurs during each step. The performance of the sc-AFM gantry nanopositioning system is evaluated and a representative nanofeatured flexible material, the wing of a Queen Butterfly, is used as a test artifact to demonstrate the efficacy of the nanometrology data acquired. This capability represents a wholly new method for in-line metrology in roll-to-roll nanomanufacturing.

Vibration Analysis and Control of AFM Microcantilever Based on the MCS Theory Using the FSMC Control in the Air

This study is aimed to find out the relation between the vibration motion and control of an atomic force microscope (AFM) piezoelectric microcantilever for free and forced vibrations in the air environment. In fact, the MC is the most important part of AFM, performing the most vital operations. Hence, the dynamic analysis and control of the MC are mandatory to obtain optimal performance. Enhancing the optimization of this system increases the sampling rate as well as the accuracy and resolution of the obtained images. MCs with a piezoelectric layer possess a higher speed and accuracy compared to conventional MCs which are simpler and less expensive. Also, in the MC vibration modeling, the Timoshenko beam model based on the modified couple stress theory is used. Next, using the Hamilton’s principle, the MC motion equations are derived by considering the geometric discontinuities as a result of the piezoelectric layer and two electrode layers. These equations are solved by using the finite element method. The MC frequency and time responses at different distances from the sample surface are obtained and compared with experimental results. In addition, the sample surface topography in the non-contact mode when the MC passes through different roughnesses in the first and second vibration modes has been investigated. Moreover, the fuzzy-sliding mode control (FSMC), which is a robust control method, is employed due to uncertainties when modeling the system. The results are compared with those of the sliding mode control (SMC) and PID control methods. For the cases of far from the surface and close to it, the MC is actuated by the piezoelectric layer and piezo-stack base, respectively. The proposed FSMC control can properly reduce chattering in the SMC to improve the results.

Probing electromechanical behaviors by datacube piezoresponse force microscopy in ambient and aqueous environments

For assisting the in-depth investigations of widespread electromechanical phenomena in functional materials, piezoresponse force microscopy (PFM) has gradually evolved to realize full information-flow acquisition and fit the conductive liquid working environments. Here, we designed data cube (DCUBE) based PFM to collect the electromechanical effect into a high-dimensional array of piezoresponse by adding ac bias with a wide range of frequencies to the probe. The electromechanical and mechanical spectra can be consecutively extracted at each pixel in the intermittent-contact mode. High-resolution ferroelectric domains of the poled LiNbO3 were mapped, corresponding to the ideal phase contrasts of about 180° in air, decane, and deionized water. Rich information detection and non-contact mode in DCUBE-PFM bring many merits on the electromechanical characterizations, especially for elastic-inhomogeneous surfaces and soft materials. Moreover, we systematically reveal the Debye screening effect and time-resolved field-oriented ion dynamics, which play crucial roles in the reduction of PFM spatial resolution in electrolytes. These physical discussions provide strategies to further realize high-resolution electromechanical imaging in highly conductive liquid environments.

Modeling of triboelectric charge accumulation dynamics at the metal–insulator interface for variable capacitive structures: application to triboelectric nanogenerators

This paper presents a dynamic model to study triboelectric charge accumulation in a variable capacitive structure with metal–dielectric interface. The presented model addresses a serious flaw of current published theoretical works related to modeling of triboelectric energy harvesters. Electrostatic analysis of the device in the contact and non-contact modes is performed. Based on the analysis of the non-contact mode, a novel technique is introduced to measure stable parasitic triboelectric charge density on the surface of the dielectric layer. Theoretical analysis for positive and negative charge accumulation is performed separately and key characteristic equations of both cases are extracted. A new measurement technique is developed to assess triboelectric charge build-up on the surface of the dielectric layer by employing a simple bridge rectifier as a test circuit. Based on the measured data, a time-dependent exponential model is suggested for triboelectric charge accumulation on the surface of the dielectric layer. The presented dynamic model is a vital asset in modeling dynamic output of triboelectric nanogenerators (TENG’s). The results show that failure to consider triboelectric charge dynamics in modeling of TENG’s would result in more than 50% error in the simulated output characteristics. Charge accumulation A new surface charge evaluation technique is introduced. Triboelectric charge accumulation on the surface of dielectrics is calculated and modeled using a simple half-wave rectifier. To get to the model, discrete charge-time points are measured. The dynamic charge model presents an essential asset in simulation of the output performance of TENG’s. positive and negative charge build up is measured.

Application of scanning ion conductance microscope in cell characterizations

Cell morphology, electrical and mechanical functions are of great significance in cell biology. However, traditional cell characterization methods are not suitable for study of living cells in a non-invasive, in situ and micro/nano-scaled way. As a new type of scanning probe microscopy, scanning ion conductance microscopy (SICM) enables non-invasive, high-resolution and real-time imaging of living cells based on its non-contact scanning mode and usage of nanopipette as its probe. In recent years, SICM has been widely applied in cell biology and cell characterizations. This review mainly introduces the SICM applications in cell characterizations. First, we introduce the instrumental composition, working principle and three work modes of SICM, and compare the strengths and weakness of the three working modes. Then the applications of SICM in cell morphology, cellular electrical and mechanical properties are described in detail. In addition, in contrast to the traditional cell characterization methods, SICM has the distinct advantages in in situ characterization of cells. Finally, the challenges of SICM in cell characterizations are discussed and its future development is proposed.

Local permittivity measurement of dielectric materials based on the non-contact force curve of microwave atomic force microscopy

We report a non-contact and quantitative method to measure the local permittivity of dielectric materials with a nanometer-scale spatial resolution. A theoretical model based on near-field approximation was developed to describe the effect of a microwave on the interaction between a probe and a sample. Under the non-contact mode, we successfully measured the force curves of Si, Al2O3, Ge, and ZrO2 using microwave atomic force microscopy and observed the variation in the force caused by the microwave. According to the established theoretical model, a quantitative non-contact evaluation of the local permittivity of dielectric materials was performed.

378 - Ho:YAG laser lithotripsy in non-contact mode: Optimization of fiber to stone working distance to improve ablation efficiency

378 - Ho:YAG laser lithotripsy in non-contact mode: Optimization of fiber to stone working distance to improve ablation efficiency

A Plane Projection Based Method for Base Frame Calibration of Cooperative Manipulators

Base frame calibration is the foundation for the cooperative work of manipulators. The commonly applied method usually constructed a matrix equation. The contact-mode approach is limited by the insufficient accuracy and efficiency while the high cost impedes the application of methods with the noncontact mode. In this paper, a projection-based method is proposed. All the transformation parameters can be solved based on the geometric constraints. When cooperative manipulators form the closed-chain asynchronously, the topological structure is projected into a particular plane. The rotation angle and translation parameters can be determined with utilization of trigonometric functions and a simple calculation process. The greatest novel feature of this analysis is that only two calibration points are required. The experiment result shows that both the accuracy and efficiency can be much better in the asynchronous calibration.

Highly sensitive, reliable and flexible piezoresistive pressure sensors featuring polyurethane sponge coated with MXene sheets

Flexible pressure sensors still face a great challenge to combine fast frequency response, wide pressure range, multiple detection modes, satisfactory mechanical and environmental stability, and simple fabrication process into a sensor. Herein, flexible piezoresistive pressure sensors are fabricated by treating the backbone of polyurethane (PU) sponge with chitosan (CS) to obtain positively charged CS@PU sponge, followed by dip-coating of negatively charged Ti3C2Tx MXene sheets. The resulting MXene@CS@PU sponge-based sensor provides a versatile sensing platform with potentials for detecting both small and large pressure signals. Due to the highly compressive resilience of the PU sponge and its polar interaction with the MXene sheets, the MXene@CS@PU sensor has high compressibility and stable piezoresistive response for compressive strains of up to 85% with a stress of 245.7 kPa, and it also exhibits a satisfactory reproducibility for 5000 compression-release cycles. Even after washing in water for 1 h, the sensor still shows good performances. With a rapid response time of only 19 ms and a low detection limit of 30 μN corresponding to a pressure of 9 Pa, the MXene sponge sensor is promising for detecting human physiological signals and insect movements. In addition to the contact mode detection, the sponge sensor could detect voices and human breaths by a non-contact detection mode.

Utilisation of antimicrobial photodynamic therapy as an adjunctive tool for open flap debridement in the management of chronic periodontitis: A randomized controlled clinical trial

Antimicrobial photodynamic therapy (aPDT) has proved to be an effective adjunctive modality with potential benefits in the management of chronic periodontitis. The combination of photothermal and photodynamic effects of Indocyanine green (ICG) dye, when it is photoactivated with a diode laser of 810 nm wavelength, has been well documented in literature. This study was conducted to evaluate whether a single session of antimicrobial photodynamic therapy using ICG dye-810 nm diode laser combination can provide a substantial benefit when it is utilised as an adjunct to open flap debridement (OFD) in the management of chronic periodontitis. Following thorough scaling and root planing, a comparative split mouth randomized controlled clinical trial was carried out on 20 recruited subjects who provided one test (OFD + aPDT) and one control site (OFD alone) each (total 40 treatment sites). The test group was subjected to a single episode of aPDT using ICG photosensitiser dye (1 mg/ml) activated with 810 nm diode laser. The laser was used in a continuous wave, non-contact mode at a power output of 100 mW applied for 30 s/spot (the total of 4 spots per tooth) and delivered by 400 μm fibre, to provide a fluence (energy density) value of 0.0125 J/cm² per spot and generate a total energy of 3 J. The following clinical parameters were assessed at baseline and 3 months: probing pocket depth (PPD), relative attachment level (RAL), relative gingival margin level (RGML), plaque index (PI), gingival index (GI), and gingival bleeding index (GBI). Intragroup and intergroup comparison was performed using paired t-test and independent samples t-test respectively. Intragroup comparison revealed a statistically significant improvement from baseline visit (p < 0.05). Intergroup comparison showed a statistically significant improvement in RAL, RGML and GI in the test group (p < 0.05). Utilisation of ICG dye activated with 810 nm diode laser, which mediated aPDT, has demonstrated surplus clinical improvement following OFD in the management of chronic periodontitis.

Higher modes and higher harmonics in the non-contact atomic force microscopy

The present paper proposes a new mathematical approach to study the role of higher harmonics and higher mode shapes in the dynamics of an atomic force microscope microcantilever. The basic principle of the present method, called the direct harmonic balance, is similar to the well-known method of harmonic balance, but the key difference is that this method does not require discretizing the partial differential equation, governing the probe dynamics. In contrast to the traditional harmonic balance, the direct harmonic balance method, introduced here, attacks the partial differential equation directly, leading to a more efficient solution procedure. The accuracy of this method is demonstrated using a perturbation method. The direct harmonic balance method is then employed to investigate the nonlinear oscillations of the atomic force microscope probe in the non-contact mode. The significance of higher mode shapes and higher harmonics is illustrated through several frequency-response curves, presented for various cases. It is found out that while higher modes are more sensitive to the amplitude of excitation, they have a smaller frequency shift. It is also found out that the second harmonic exhibits high sensitivity to the initial tip/sample separation distance. In addition, it is shown that reducing the tip/sample initial distance results in a considerable growth in the magnitude of the second harmonic, which can be used as a reliable signal to explore topography of the sample.

Dentinal Hypersensitivity Treatment Using Diode Laser 980 nm: In Vivo Study.

The discomfort of patients due to dentinal hypersensitivity (DH) is one of the main challenges that dentists face in daily practice. Difficulties in DH treatment gave rise to many protocols which are currently used. The aim of this clinical study is to evaluate the effectiveness of a new protocol on the reduction of dentinal hypersensitivity with diode laser 980 nm and the application of a graphite paste. 184 patients enrolled in the study, the degree of pain was evaluated by visual analog scale (VAS), graphite paste was applied on the exposed dentine before irradiation, the application of diode laser 980 nm with continuous mode, backward motion, tangential incidence of the beam in non-contact mode and a delivery output of 1 W. Fiber’s diameter was 320 μm and total exposure time depended on the time necessary to remove the graphite paste from the teeth. Statistical analyses were performed with Prism 5® software. Pain in post-operative significantly decreased immediately after the treatment. Mean values stayed stable until a 6-month follow-up. The application is considered to be safe with long-term effectiveness.

The effects of deposition time on the nanoscale patterns of Ag/DLC nanocomposite synthesized by RF-PECVD.

In this study, a stereometric analysis of the three dimensional (3-D) surfaces of the Ag/DLC nanocomposite synthesized by RF-PECVD was performed. Atomic force microscopy in noncontact mode was used to study surface morphology in correlation with multi-parametric statistical analysis. The associated parameters of segmented motifs in conformity with ISO 25178-2:, 2012 have been extracted using MountainsMap® Premium software. The mathematical algorithm computes detached watersheds of hill or dale motifs and determines the maximum and minimum points of motifs. The stereometric analyses with MountainsMap® Premium software provided detailed information on the 3-D surface topography of samples. Fractal analyses revealed the fractal nature of the performed samples is in correlation with the deposition time of samples. Detailed information of manufactured Ag/diamond-like carbon (DLC) nanocomposite is given based on the information about the surface structure, properties, and performance characteristics. The performed analysis allows the high-resolution modeling of Ag/DLC nanocomposite surface microtexture with motif analysis (intrinsic characteristics disclosure and characterization of surfaces fractal), in order to be included in computer interactive simulation algorithms. It was found the fractal dimension decreases with the increase of the deposition times on samples.

A multiscale flexible pressure sensor based on nanovesicle-like hollow microspheres for micro-vibration detection in non-contact mode.

To detect micro-vibration, flexible pressure sensors require that the sensing materials possess superior sensitivity in non-contact sensing mode. One type of matter, nanovesicles, has the characteristics of hollow spheres and crack junctions in a single body, and provides an exciting bionic idea to explore high-sensitivity sensing materials. Hence, in this study, novel hollow microspheres with a hierarchical nanovesicle-like architecture are designed, prepared via a controlled strategy of adjusting the surface energy, and employed to fabricate multiscale flexible pressure sensors that display a high response sensitivity of 11.3 kPa-1 and a low detection limit of 5.5 Pa with good stability for 2500 cycles. The working mechanism can be deduced as the synergistic effects from the stress concentration of microstructural patterns and the successive deformation of the nanovesicle-like structure, which is revealed by controlled experiments and finite element method simulations. The as-assembled flexible pressure sensor is used to detect the dynamic micro-vibration signals caused by fluid motion (water flow and airflow) and inelastic/elastic collision in non-contact mode, revealing good sensitivity, repeatability and stability. This work provides theoretical and experimental evidence for the development of hierarchical structure-based highly sensitive flexible sensors in the future.