Soft Pad Research Articles

Mechanics of wet adhesion in soft interaction with patterned morphology

Locking surfaces with a wet interface can enhance interactions between a grasped object and a soft pad. This paper presents a mechanical approach to understanding the role of morphological design in achieving wet adhesion for secure grasping by a soft pad. Two conditions were compared in modeling wet interfaces between an object and a soft pad: a pad with a flat surface, and a pad with a micropatterned surface. The latter was designed and analyzed based on the wet attachment between the surface of a tree-frog’s toes and its substrate. In this model, we proposed a method to estimate the contact force in both normal and tangential directions between a soft pad with a micropattern surface and a rigid flat surface substrate. A square mold containing 3600 85 μm × 85 μm cells interspaced by grooves 15 μm wide and 15 μm deep was fabricated, using e-beam technology, as the micropattern pad. The generated normal and tangential contact forces of the pad with a micropattern surface, and a pad with a flat surface were measured in both normal and tangential directions under wet conditions. Experimental results showed good agreement with theoretical results, indicating that the micropattern significantly enhanced the contact force of the pad by approximately two-fold for the normal and 1.2- to 1.4-fold for the tangential force. This theoretical approach can be potentially utilized to investigate the association of soft pad morphology with wet adhesion, and enhance efficient grasping by soft robotic hands in wet and high-moisture environments.

Stretchable Suction Cup with Electroadhesion

AbstractSuction cups are commonly used as adhering and grasping devices. This study proposes a methodology to expand the applicability of suction cups. A suction cup is developed with a soft pad which consists of stretchable electrodes and insulating layers that bond to the bottom of the main body of the suction cup. When the stretchable electrodes generate an electrostatic attraction between the electrodes and the object, the pad deforms, filling the gaps between the pad and the object. Due to the soft pad, the amount of incoming air is significantly reduced compared to a normal suction cup. Experiments reveal the effect of these features. Applying a high voltage to the stretchable electrodes increases the holding success ratio of the suction cup in the normal direction for smooth and rough surfaces due to the stretchable electrodes. Measuring the negative pressure inside the suction cup confirms that the electrostatic force maintains the adhesion force on both smooth and rough surfaces. Thus, the electrostatic force and stretchability of the soft pad greatly increase the adhesion force of the suction cup. Furthermore, the electrostatic force prevents a slip of the suction cup, which improves the performance of the suction cup.

A model of a discretely supported railway track based on a 2.5D finite element approach

The dynamic properties of a railway track are important for both the generation of rolling noise and the development of rail corrugation. A conventional track consists of long rails mounted periodically on transverse sleepers and supported in ballast. In order to improve the predictions of the noise and vibration of the track, a model of a discretely supported track is proposed based on the so-called 2.5 dimensional (2.5D) finite element approach, which is used to model an infinite free rail. This is coupled to a finite number of sleepers, by means of an array of springs representing each rail pad, using a receptance coupling method. The sleepers are represented by flexible beams, supported on an elastic foundation. Results are presented in terms of the point mobility and track decay rate and these are compared with the corresponding field measurements for two tracks, one with soft rail pads and one with stiff rail pads. Very good agreement is found between the predictions and the measurement results, especially for the track with soft rail pads. The flexible sleeper model is shown to give improved results compared with a rigid mass model, especially for the track with stiff rail pads.

A Variable Stiffness Robotic Gripper Based on Structure-Controlled Principle

This paper presents a novel structure-controlled variable stiffness robotic gripper that enables adaptive gripping of soft and rigid objects with a wide range of compliance. With the structure-controllable principle, the stiffness is controlled by the mechanical structure configurations rather than by material properties or electronic means. The principle is realized by changing the effective second moment of area of the gripper finger through rotating a built-in flexure hinge shaft. Based on this principle, the states of the stiffness can be continuously, instead of discretely, studied and assessed over the intermediate states from compliant to almost completely rigid. A variable stiffness mechanism has been developed to demonstrate the validity of the proposed principle. It enables that the finger stiffness and gripping position are independently controlled. With the introduction of flexure hinges, the undesired lateral buckling resulted from the rotation of a normal leaf spring is eliminated. In addition, a two-finger parallel gripper with this variable stiffness mechanism is developed which can provide the grasping stiffness according to the grasping task requirements. The effectiveness of the gripper has been demonstrated to handle the objects range from light, fragile to heavy, rigid without using any feedback loop or soft pads. Note to Practitioners —This work was inspired by the fact that the capability of variable stiffness in the robot actuator can reduce the undesired impacts to the robot arms. It can also allow a safer interaction between robot and human. Gripping of objects with uncertainties in shapes and position, as well as large variations in fragility and weight can also benefit from the concept of the variable stiffness. However, existing designs of variable stiffness grippers either have limited stiffness range or bulky configurations. They compromised the practical applications. This paper introduces a design in that a rotating flexure hinge shaft is embedded inside the robotic gripper finger. The mechanical stiffness of such fingers can be varied by changing the rotation angle of the flexure hinges. We present the working principle supported by mathematical models in the design and development. We also show an example design of a two-finger parallel gripper equipped with the VSFs. Extensive experiments demonstrated that the gripper is effective in gripping objects with wide range of uncertainties. Such gripper design avoids the use of soft pads as well as closed-loop control and high-precision sensors. In the future work, we shall implement such grippers for actual industrial applications.

Numerical and experimental study on noise reduction of concrete LRT bridges

Rolling noise and structure-borne noise radiating from the bridge are two major sources of noise in light rapid transit (LRT) bridges. To control the noise radiation from LRT bridges, an efficient numerical method for noise prediction is needed. In this study, a combined three-dimensional dynamic model and 2.5-dimensional acoustic model were used to investigate noise reduction in a rail and in a U-shaped girder bridge. The effects of three noise mitigation measures on noise control were then compared: installation of a noise barrier, use of a rail pad with a lower stiffness, and use of a floating ladder track. The corresponding noise reduction was investigated using the numerical method. A field test was conducted to validate the noise reduction effects. It was found that the noise barrier was more effective in reducing the rail noise, and the soft rail pad is more effective to control the bridge noise. The floating ladder track can significantly reduce bridge vibration, but the excessive vibration of the ladder track itself became another major noise source. The findings should guide the selection of appropriate mitigation measures for noise reduction in LRT bridges.

Antibiotic ointment versus a silver-based dressing for children with extremity burns: A randomized controlled study

IntroductionAntibiotic or silver-based dressings are widely used in burn wound care. Our standard method of dressing pediatric extremity burn wounds consists of an antibiotic ointment or nystatin ointment-impregnated nonadherent gauze (primary layer), followed by rolled gauze, soft cast pad, plaster and soft casting tape (3M™ Scotchcast™, St. Paul, MN). The aim of this study was to compare our standard ointment-based primary layer versus Mepitel Ag® (Mölnlycke Health Care, Gothenburg, Sweden) in the management of pediatric upper and lower extremity burn wounds. MethodsChildren with a new burn injury to the upper or lower extremities, who presented to the burn clinic were eligible. Eligible children were enrolled and randomized, stratified by burn thickness, to be dressed in an ointment-based dressing or Mepitel Ag®. Study personnel and participants were not blinded to the dressing assignment after randomization. Dressings were changed approximately once or twice per week, until the burn wound was healed or skin-grafted. The primary outcome was time to wound healing and p-value < 0.05 was considered significant. ResultsNinety-six children with 113 upper or lower extremity burns were included in the analysis. Mepitel Ag® (hazard ratio [HR] 0.57 (95% Confidence Interval (CI) 0.40–0.82); p = 0.002) significantly reduced the rate of wound healing, adjusting for burn thickness and fungal wound infection. The incidence of fungal wound infections and skin grafting was similar between the two groups. Children randomized to standard ointment dressings were significantly less likely to require four or more burn clinic visits than those in the Mepitel Ag® (4% versus 27%; p = 0.004). ConclusionOur study shows that our standard ointment-based dressing significantly increases the rate of wound healing compared to Mepitel Ag® for pediatric extremity burn injuries. Level of evidenceTreatment study; Level 1.

Injuries and Complications Management with Forsus Appliance

Introduction: Forsus is a useful appliance for non-compliant Class II problems, however various problems can occur when using them.Objective: To demonstrate a comprehensive series of of critical situations that can occur using the Forsus device and to provide the possible solutions of each complication.Materials &amp; Method: The clinical management of the Forsus appliance was analyzed for eighty consecutively treated patients. The Forsus was used five months on average and pictures and clinical record were registered each time a patient had a problem or an injury.Discussion: The most common problem was breakage of the appliance. Breakage could occur as debonding of the lower first premolars or unsoldering of the upper first molar tubes. Lower premolar debonding could be prevented and fixed with an extra layer of flow composite surrounding the bracket base. Lesions of the cheek mucosa were found in several patients. A soft cotton pad used as “wax” was an effective solution to allow soft tissue healing and to prevent spring rubbing against the cheek. Upper molar intrusion occurred mainly when second molars were not included in the upper arch. Some patients experienceddisconnection of the spring and the push rod while opening the mouth wide. They were taught to self-adjust the appliance.Conclusion: The use of the Forsus appliance may lead to relatively frequent problems that the orthodontist can easily preventand manage.

An Air-Filled Pad With Elastomeric Pillar Array Designed for a Force-Sensing Insole

Studies on footwear-based wearable devices for gait and motion monitoring have been conducted by many researchers, and the force measurement of a foot is one of the most important topics among them. In this paper, we present the design of a soft force-sensing pad for in-shoe force measurement. A force-sensing method based on an air pressure sensor is utilized to robustly measure the force caused by compression in a shoe. To withstand the human weight, an air-filled structure with an elastomeric pillar array is designed. The force is measured by the increase in air pressure caused by pillar compression. Due to the simple sensing structure, it has the advantage that it can be made into various forms such as an insole pad. To verify the sensing performance, experiments are performed to compare its accuracy, hysteresis, and repeatability with an off-the-shelf load cell. The measured results show an accuracy error of 0.249 kgf, a hysteresis error of 1.071 kgf, and a repeatability error of 0.202 kgf. To verify the robustness of the proposed sensing pad, accuracy and precision change under nine different compression conditions is calculated, and the results show an accuracy error of 0.672 kgf. Moreover, error variation of the proposed sensing pad is about four times smaller than the widely used force-sensing resistor sensor.

A Soft Casting Technique for Managing Pediatric Hand and Foot Burns.

Hand and foot burns in children are difficult to dress. The authors have developed a soft casting technique to manage burns to these areas. The aim of this study is to report the outcomes using weekly dressing changes with a soft casting technique to manage pediatric hand and foot burns in the outpatient setting. A retrospective chart review was performed on children with burns to the hands or feet, who underwent dressing changes with a soft casting technique at the Children's Hospital Colorado Burn Center. Soft casting was performed by placing antibiotic ointment-impregnated nonadherent gauze over the burn wound(s), wrapping the extremity using rolled gauze, applying soft cast pad, plaster, soft cast tape, and an elastic bandage. This was changed weekly. Two hundred ninety-eight children with hand burns had a mean age of 16.8 ± 2 months. Two hundred forty-eight children had partial thickness burn injuries (83%), 50 had full thickness burn injuries (17%), and the mean total body surface area (TBSA) was 1 ± 2.4%. The mean time to heal was 10.1 ± 1.7 days for all subjects. Sixty-six children with foot burns were identified with a mean age of 24 ± 2.6 months. Forty-six children had partial thickness injuries (70%), 20 had full thickness burn injuries (30%), and the mean TBSA was 2.3 ± 2.9%. The mean time to heal was 14.1 ± 2.2 days for all subjects. Weekly dressing changes using a soft casting technique are effective for the outpatient management of pediatric hand and foot burns. This method avoids costly inpatient hospital care, reduces the number of painful dressing changes, and allows children to heal in their own environment.

Copper Chemical Mechanical Polishing Performances of Polystyrene/Ceria Hybrid Abrasives with a Core/Shell Structure

The core/shell structured hybrid abrasives, featuring polystyrene (PS, 280–300 nm in size) cores and ceria (CeO2, 10–20 nm in thickness) shells, were introduced into copper chemical mechanical polishing (CMP) processes. The slurry chemistry based on the synergy among glycine–hydrogen peroxide-benzotriazole was used in combination with the obtained polystyrene/ceria (PS/CeO2) abrasives. Moreover, the use of a medium/high-hardness pad (IC-1000) was compared to the use of a soft pad (MD-Chem). The copper CMP characteristics were evaluated in terms of material removal rate, surface roughness as well as cross-sectional profile analyses. After CMP with PS/CeO2 hybrids in combination with a soft pad, the average roughness of copper layer decreased from 1.89 to 0.56 nm, and a mean removal rate of 254 nm/min was achieved. With respect to conventional ceria particles, the PS/CeO2 hybrid abrasives contributed to the reduction of the mechanical damage and the number/depth of scratch/pit. The improved copper CMP performances might result from the reduced overall hardness and elastic modulus of PS/CeO2 hybrid particles. These experimental results revealed that the PS/CeO2 composite abrasives further presented potential CMP applications for mechanically challenging materials such as copper and low-k dielectrics.

Electromyographic analysis of balance exercises in single-leg stance using different instability modalities of the forefoot and rearfoot

PurposeTo investigate the activity of lower extremity muscles in response to single-leg stance on a training device, destabilizing the forefoot while the rearfoot stands on a fixed plate and vice versa compared with a balance pad and the floor. DesignCross-sectional study. SettingUniversity's laboratory. ParticipantsTwenty-seven healthy adults. MethodsSurface electromyography and 2D video analysis were used to record the activity of lower extremity muscles and to control sagittal knee joint angle during single-leg stance trials under one stable control condition and five unstable conditions. ResultsThe majority of lower extremity muscles were significantly more active when the forefoot was destabilized while the rearfoot remained stable compared with the stable condition and the conditions where the forefoot was stable and the rearfoot unstable (p <0 .001). Mean change of knee joint angle was significantly increased under the conditions rearfoot stable/forefoot unstable (p = 0.001). The soleus muscle activation was significantly increased when balancing on the balance pad (p < 0.001). ConclusionsIncreased activity in the majority of lower extremity muscles and sagittal knee joint angles indicate that destabilizing the forefoot while the rearfoot remains stable is the most challenging balance task. Soleus muscle activation increased when performing ankle plantarflexion on the soft balance pad.

Prospective evaluation of the safety and feasibility of a pelvic floor dilator during active labor.

The objective was to assess the safety and feasibility of using a pelvic floor dilator during active labor to prevent injuries to the levator ani muscle (LAM) and perineum. In a prospective pilot study, a pelvic floor dilator using soft pads was introduced into the vaginal canal to gradually expand the vagina, in 30 nulliparous women and in 10 controls. The primary outcomes were adverse events related to the device. Secondary outcomes were perineal lacerations after delivery, sonographically defined levator ani injury, hiatal area dimensions, and anal sphincter disruption, all at 12-20weeks postpartum, and maximum pelvic floor dilation, time to achieve maximum dilation, and device retention rate. From October 2014 through November 2016, a total of 494 women were screened, and 61 consented to the study. Thirty women used the device and 27 returned for follow-up. No maternal or neonatal injuries were related to use of the dilator. The average maximum dilation of the vaginal canal was 7.4cm (SD 0.7, range 5.5-8.0). Dilation time averaged 27min (SD 13, range 5-60). Device insertion adjustment was needed in 13 out of 30 cases (43%). Similar rates of 3th-4th degree perineal lacerations were seen in both groups. Levator ani avulsion was diagnosed in 2 out of 27 (7%) in the device group and in 1 out of 9 (11%) in the control group (p = 0.2). The rate of partial injury in the device group was 2 out of 27 (7%) vs 2 out of 9 (22%) in the comparison group (p = 0.2). The use of the pelvic floor dilator during active labor is feasible. No safety issues were identified.

A New Soft Pneumatic Elbow Pad for Joint Assistance With Application to Smart Campus

This paper presents an assistance equipment of human elbow joint, which aims to help patients who have elbow injury issues in smart campus environment. A new type of soft pneumatic elbow pad (SPEP) which adopted soft material manufacturing technology is presented. Compared with the rigid assistant equipment, the SPEP shows more comfort, smaller equipment size, and convenience of wearing. Meanwhile, three different types of sensors (the air pressure sensor, bending sensor, and force sensor) are used in the SPEP to discover the two important characteristics which are applied. In order to verify the effectiveness of the designed SPEP, two analysis methods are presented. The surface electromyogram signal and the root mean square analysis are used in the first method, which prove that the SPEP could reduce the activity of the muscle and assist power during the elbow movement. Compared with the first method, the second method which is the model of calculation after wearing SPEP can obtain specific value of assisting power in the biceps and olecranon. Thus, the aforementioned methods illustrate the feasibility of the SPEP. Finally, in order to make the SPEP used in daily life, a portable backpack with the control system and the energy system is applied to the field of human assistance equipment.

A Review of Bin Filling Technologies for Apple Harvest and Postharvest Handling

Abstract. Bin fillers play a critical role in transporting and distributing fruit evenly and without bruising into individual bins or containers from harvest platforms infield or sorting lines in the packinghouse. Over the years, a large variety of bin fillers have been developed for infield use and postharvest handling. This article reviews different bin filling technologies in terms of major design features, performance, and throughput, as well as automatic control and safety features. For infield use, bin filler designs have evolved from the early use of conveyors and reciprocating plates to recent adoption of soft pads and foam rollers, to reduce bruising and improve fruit distributions. For postharvest use, tilted bins and conveyors commonly used with early bin fillers have been replaced with hinged trays and vacuum suction cups for fruit transport and cylinder brushes and swingable dividers for bruise prevention. While many types of bin fillers have been developed, few are suitable for infield use because it imposes more constraints than postharvest use. Despite the use of automatic sensing and control in most bin fillers, human assistance is still needed during their operation. There are still major issues with the current bin fillers, such as large size, complexity in design, uneven fruit distributions, and low throughput. Further effort should, therefore, be directed towards the development of high throughput, simple yet reliable, compact and fully automated, or even intelligent bin fillers for infield and postharvest use. Keywords: Apple, Automation, Bin filler, Harvest, Infield, Postharvest handling.

A Comprehensive Protocol to Prevent Brachial Plexus Injury During Ankylosing Spondylitis Surgery

This article describes a comprehensive protocol to protect the brachial plexus when performing pedicle subtraction osteotomy for ankylosing spondylitis patients with thoracolumbar kyphosis. A descriptive study was conducted. Records of 101 cases from October 2013 to December 2016 were retrospectively audited. The protocol included five items: (1) preoperative assessment of motion range and nerve function of limbs and trunks; (2) preoperative positioning according to the assessment results; (3) intra-operative somatosensory evoked potential and blood pressure monitoring; (4) intra-operative repositioning according to the monitoring alarm signals; and (5) postoperative neurological function check. Five patients showed impending brachial plexus injury indicators, including two who had a decrease in blood pressure and threewho had a decrease in the amplitude of somatosensory evoked potential. After adjustment of position and soft pads, one patient had brachial plexus injury (0.99%) and the recovery time was 2weeks. With this comprehensive strategy, the brachial plexus could be effectively protected during the surgery.

Force attenuation capacity and thermophysiological wear comfort of vertically lapped nonwoven fabric

Hip-protective pads are designed to prevent hip fracture in elderly women. Two types of vertically lapped nonwoven fabrics were evaluated for suitability as materials for hip-protective pads. The force attenuation capacity of pads made from these fabrics was studied using drop impact tests, and performance relevant to thermophysiological wear comfort measured using a sweating guarded hot plate. The results indicate that vertically lapped nonwoven fabrics are suitable materials for soft hip-protective pads. They provide effective protection for the hip bone, and have similar force attenuation capacity to closed-cell foam. The inter-fibre and voids in nonwoven structures enable moisture to escape to the environment, and the experimental vertically lapped nonwoven fabric pads had significantly higher ability to transfer moisture than closed-cell foam pads.

ANALYSIS OF DYNAMIC EFFECTS ACTING ON RAILWAY CROSSINGS

The paper is focused on measurement and analysis of dynamic effects on railway turnouts. Two same-type turnouts with different fastening elasticity were chosen. Attention was focused mainly on the crossing part of the turnout, where the highest dynamic impacts occur. The point of the paper is the assessment of influence of soft rail pads on spread of dynamic energy through the construction.

Experimental investigation into temperature- and frequency-dependent dynamic properties of high-speed rail pads

In order to investigate the temperature- and frequency-dependent dynamic properties of high-speed rail pads excited by rail vehicle’s large-amplitude quasi-static loads due to bogie interval and wheelset spacing, the soft pads from WJ-7, WJ-8 and Vossloh 300 fasteners frequently used in China’s high-speed railway track systems are taken as test subjects. At first, a series of dynamic tests of the three high-speed rail pads at a specific frequency of 0.3Hz and under various low temperatures ranging from −60 to 20°C are carried out. Then, the Time-Temperature Superposition (TTS) and Williams-Landel-Ferry (WLF) formula are used to predict their dynamic performance at frequencies higher than the test frequency, and the Fractional Derivative Kelvin-Voigt (FDKV) model is proposed to represent their frequency-dependent dynamic properties. Finally, the frequency-dependent dynamic performance of the three high-speed rail pads under rail vehicle’s small-amplitude dynamic loads due to the surface roughness of rail and wheel is discussed. It is found that the storage stiffness of WJ-7, WJ-8 and Vossloh 300 rail pads is sensitive to low temperatures, as well as much larger than their corresponding loss stiffness. The glass transformation temperatures of WJ-7, WJ-8 and Vossloh 300 rail pads are −40, −45 and −45°C, respectively. The FDKV model can basically give a satisfactory fitting with the experimental results within 100Hz, especially at ordinary temperatures. The dynamic properties of rail pads excited by rail vehicle’s small-amplitude dynamic loads are time-variable and related to rail vehicle’s large-amplitude quasi-static load values on rail pads. Thus, it is very important that the temperature- and frequency-dependent dynamic parameters of the polymer materials in vehicle-track systems must be measured according to the specific operation conditions, since otherwise an accurate prediction of the broadband train-induced vibration and noise at different temperatures is difficult to achieve.

The Experimental Study on Mechanical Polishing on Materials with Hydrolysis Reaction

The hydrolytic properties of LiAlO2 (LAO) are important factors for its applications on LED fabrication. During soft pad polishing process, the H2O in the slurry is deleterious for LAO surface polishing results. The current study develops a material removal rate model for materials with hydrolysis reaction to predict the result of polishing process.The current research conducts the experimental studies to investigate the material removal rate and its mechanism during the soft pad polishing process. In the experimental study, the hydrolytic properties of LAO have been tested to understand the hydrolysis speed with different operation parameters to assist the development of the theoretical model. Also the material removal rates of LAO with hydrolytic property have been measured under different soft pad polishing operating conditions. The experimental results provide the hydrolytic properties of LiAlO2 to understanding of the mechanism on polishing process.

Radiofrequency ablation of the lateral palatal space for snoring.

ObjectivePilot study to examine the effect of radiofrequency ablation (RFA) of the lateral palatal fat pad in patients with socially-disruptive snoring.MethodSnoring outcomes and complications were compared between a group of patients with treated with RFA ablation of the lateral soft palate fat pad with or without inferior turbinate reduction (8 patients) and another group undergoing inferior turbinate reduction alone (12 patients).ResultsSnoring loudness and bothersomeness improved in the palate but not inferior turbinate group. Pain was mild and no major complications were observed.ConclusionThe study supports RFA ablation of the lateral palatal space as a potential low morbidity procedure for snoring.