Variable-Sensitivity Force Sensor Based on Structural Modification

Force sensors are used in a wide variety of fields. They require different measurement ranges and sensitivities depending on the operating environment because there is generally a trade-off between measurement range and sensitivity. In this study, we developed a variable-sensitivity, variable-measurement-range force sensor that utilizes structural modification, namely changes in the distance between the force application point and the detection area, and changes in the cross-sectional area. The use of shape-memory materials allows the sensor structure to be easily changed and fixed by controlling the temperature. First, we describe the theory of the proposed sensor. Then, we present prototypes and the experimental methods used to verify the performance of the sensor. We fabricated the prototypes by attaching two strain gauges to two sides of a shape-memory alloy and shape-memory polymer plates. Experiments on the prototypes show that the relationship between the applied force and the detected strain can be changed by bending the plate. This allows the sensitivity and measurement range of the sensor to be changed.

A Comparative evaluation of the shaping ability, canal straightening, and preparation time of five different NiTi rotary files in simulated canals

Aim

The aim is to compare the shaping ability, canal straightening, and the preparation time of five different nickel-titanium rotary files in simulated J-shaped canals.

Materials and Methods

Ninety J-shaped canals in resin blocks were filled with 2% Methylene Blue solution and pre-instrumentation images were taken using a Leica microscope at a ×10. They were prepared until size 25 taper 0.04 using (n = 18 per group): T-Flex, HyFlex CM, Vortex Blue, S5, and iRace. After instrumentation, images were captured again, and composite images were made using Adobe Photoshop imaging software. The differences in canal width and canal curvature at each respective landmark were measured and compared. The preparation time and canal abbreviations were also recorded. Statistical analyses were performed using one-way ANOVA and post hoc Tukey HSD tests. The level of statistical significance was set to P = 0.05.

Results

HyFlex CM demonstrated the least difference in canal width after instrumentation, but no significant difference (P > 0.05) as compared to T-Flex and Vortex Blue. The mean canal straightening ranged between 0.91° and 7.65°. T-Flex created the least canal straightening after instrumentation which was significantly less (P < 0.05) than S5, but there was no significant difference (P > 0.05) when compared to HyFlex CM. Instrumentation with the S5 file was significantly faster (P < 0.05), whereas HyFlex CM was the slowest.

Conclusion

T-Flex, HyFlex CM, and Vortex Blue demonstrated better shaping ability, whilst T-Flex and HyFlex CM maintained the original canal curvatures well. S5 tended to straighten the canals and caused the greatest canal transportation, but it required the least amount of time to shape the canal.

Molecular Dynamics Investigation of the Influence of Voids on the Impact Mechanical Behavior of NiTi Shape-Memory Alloy

To date, research on the physical and mechanical behavior of nickel-titanium shape-memory alloy (NiTi SMA) has focused on the macroscopic physical properties, equation of state, strength constitution, phase transition induced by temperature and stress under static load, etc. The behavior of a NiTi SMA under high-strain-rate impact and the influence of voids have not been reported. In this present work, the behavior evolution of (100) single-crystal NiTi SMA and the influencing characteristics of voids under a shock wave of 1.2 km/s are studied by large-scale molecular dynamics calculation. The results show that only a small amount of B2 austenite is transformed into B19’ martensite when the NiTi sample does not pass through the void during impact compression, whereas when the shock wave passes through the hole, a large amount of martensite phase transformation and plastic deformation is induced around the hole; the existence of phase transformation and phase-transformation-induced plastic deformation greatly consumes the energy of the shock wave, thus making the width of the wave front in the subsequent propagation process wider and the peak of the foremost wave peak reduced. In addition, the existence of holes disrupts the orderly propagation of shock waves, changes the shock wave front from a plane to a concave surface, and reduces the propagation speed of shock waves. The calculation results show that the presence of pores in a porous NiTi SMA leads to significant martensitic phase transformation and plastic deformation induced by phase transformation, which has a significant buffering effect on shock waves. The results of this study provide great guidance for expanding the application of NiTi SMA in the field of shock.

Combination of mini locking plate and nitinol arched shape-memory connector for purely lateral malleolus fractures: technique and clinical results

Background

Lateral malleolus fractures occur frequently. The common techniques for fixing purely lateral malleolus fractures are often challenging, owing to the extent of soft tissue damage and fracture non-union. Herein, we report a new treatment that entails minimally invasive insertion and continuous compression of the broken ends as a novel technique, and evaluate its clinical results.

Methods

This study enrolled 21 patients (13 males and 8 females; mean age 32.06±3.45 years, range 23–69 years) with purely lateral malleolus fractures. Each patient underwent open reduction treatment with a mini locking plate for internal fixation and compression of the fracture end with an Arched Shape-Memory Connector (ASC). The clinical assessments were made using the American Orthopedic Foot and Ankle Society (AOFAS) scores, which were recorded at the final follow-up visit.

Results

The patients were followed for an average of 14.7±1.2 months (range, 12–18 months). None of the patients showed surgical failure, and all of the purely lateral malleolus fractures healed in an average of 12.6±1.5 weeks (range, 10–16 weeks). The mean AOFAS score was 88.94 (range, 83–90).

Conclusions

The new treatment had beneficial outcomes for purely lateral malleolus fractures. Mini locking plates are minimally invasive for surgical intervention, and combined with continuous concentrated compression with an ASC to accelerate osseous healing, they aid in restoration of function and enable early rehabilitation with a low incidence of postoperative complications.

Surface Analysis of Wire-Electrical-Discharge-Machining-Processed Shape-Memory Alloys

Shape-memory alloys such as nitinol are gaining popularity as advanced materials in the aerospace, medical, and automobile sectors. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape-memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. Anunconventional machining process like wire-electrical-discharge-machining (WEDM) can be effectively and efficiently used for the machining of such alloys, although the WEDM-induced surface integrity of nitinol hassignificant impact on material performance. Therefore, this work investigated the surface integrity of WEDM-processed nitinol samples using digital microscopy imaging, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. Three-dimensional analysis of the surfaces was carried out in two different patterns (along the periphery and the vertical plane of the machined surface) andrevealed that surface roughness was maximalat the point where the surface was largely exposed to the WEDM dielectric fluid. To attain the desired surface roughness, appropriate discharge energy is required that, in turn, requires the appropriate parameter settings of the WEDM process. Different SEM image analyses showed a reduction in microcracks and pores, and in globule-density size at optimized parameters. EDX analysis revealed the absence of wire material on the machined surface

Phase Transformation, Twinning, and Detwinning of NiTi Shape-Memory Alloy Subject to a Shock Wave Based on Molecular-Dynamics Simulation

Martensitic transformation, reverse martensitic transformation, twinning, and detwinning of equiatomic nickel–titanium shape-memory alloy (NiTi SMA) under the action of a shock wave are studied using a molecular-dynamics simulation. In the loading process of a shock wave, B2 austenite is transformed into B19′ martensite, whereas in the unloading process of the shock wave, B19′ martensite is transformed into B2 austenite. With repeated loading and unloading of the shock wave, martensitic transformation occurs along with twinning, but reverse martensitic transformation appears along with detwinning. The mechanisms for the twinning and detwinning of NiTi SMA subjected to a shock wave are revealed in order to lay the theoretical foundation to investigate the shape-memory effect and superelasticity.

Fast Torsional Artificial Muscles from NiTi Twisted Yarns

Torsional artificial muscles made of multiwalled carbon nanotube/niobium nanowire yarns have shown remarkable torsional speed and gravimetric torque. The muscle structure consists of a twisted yarn with half of its length infiltrated with a stimuli-responsive guest material such as paraffin wax. The volumetric expansion of the guest material creates the torsional actuation in the yarn. In the present work, we show that this type of actuation is not unique to wax-infiltrated carbon multiwalled nanotube (MWCNT) or niobium nanowire yarns and that twisted yarn of NiTi alloy fibers also produces fast torsional actuation. By gold-plating half the length of a NiTi twisted yarn and Joule heating it, we achieved a fully reversible torsional actuation of up to 16°/mm with peak torsional speed of 10 500 rpm and gravimetric torque of 8 N·m/kg. These results favorably compare to those of MWCNTs and niobium nanowire yarns.

Treatment of ingrown nail with a special device composed of shape-memory alloy

Ingrown nail is a common nail problem resulting in pain and disability in daily life. Recently, a new treatment modality for an ingrown nail was reported that used a device composed of shape-memory alloy, K-D. The aim of the present study was to determine the efficacy, recurrence rate and complications of K-D. Between June 2010 and September 2012, 24 patients (31 nails) underwent treatment of symptomatic incurved nails with a K-D. Patients were evaluated at pretreatment and during every visit. The mean age of the patients involved was 43.4 years. The mean period of follow up was 161 days. The mean maintenance period was 41 days. The right first toenail was the most common site. Almost ingrown nails healed and the nail deformity was corrected after the procedure. Among the 31 nails, seven of the ingrown nails recurred during follow up (22.6% recurrence rate). The recurrence rate of the patients with stage 1, 2 and 3 ingrown nails was 22.2%, 33.3% and 14.2%, respectively. The majority of patients were very satisfied. There were no side-effects in most patients except loss of nail in one patient. K-D has some advantages such as simple application steps, no deformity after the procedure, high patient satisfaction and obvious effect compared to other non-invasive and invasive methods.

X-ray diffraction measurements in high magnetic fields and at high temperatures

A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1 K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research.