Modeling the high-frequency complex modulus of silicone rubber using standing lamb waves and an inverse finite element method

Jonsson, Ulf G; Lindahl, Olof; Andersson, Britt M.

doi:10.1109/tuffc.2014.006471

Cited by 4 publications

(12 citation statements)

References 28 publications

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“…The configuration used to develop the look-up table procedure, comprising a piezoelectric sensor and a SRD, was identical to the systems described in Jonsson et al (2014). The reader is referred to said article for a detailed presentation of each step leading to the final expressions used with the FE solver.…”

Section: Methodsmentioning

confidence: 99%

“…As seen in equation ( 7), letting tend to 0.5 makes elements of T ij grow to infinity. A method for the PDE to handle this situation in a 2D cylindrical geometry is presented in Jonsson et al(2014).…”

Section: Boundary Value Conditions Of the Piezoelectric Sensor And Srd With Inclusionmentioning

confidence: 99%

“…As the vibrational frequency of the piezoelectric sensor approaches the first radial mode frequency, the electro-mechanical conversion between the radial displacements and the charge production of the piezoelectric sensor becomes more efficient, resulting in an increase in displacement amplitudes. To approximate this non-linear behavior in the model, a Boltzmann function (sigmoidal) was introduced as a compensating function (Jonsson et al, 2014):…”

Section: Hyper-elastic Compensating Function U(v )mentioning

confidence: 99%

“…We have shown earlier that a cylindrical FE model of a vibrating piezoelectric element in contact with a silicone rubber disk (SRD) can reproduce the electric impedance frequency response of a corresponding physical system (Jonsson et al, 2013;Jonsson et al, 2014). The FE model has the ability to, in detail, map all variations of the elastic properties of the SRD; hence, the elastic effects of an inclusion with deviating elastic properties embedded in the SRD.…”

Section: Introductionmentioning

confidence: 99%

“…The transmission behavior of Lamb waves in plates has been studied experimentally (Mori and Biwa, 2016). In the configuration used here, the piezoelectric sensor and the SRD, vibrating at frequencies near the first radial Stiff inclusions in silicone rubber resonance mode, enables symmetric Lamb waves to be established in the SRD (Jonsson et al, 2014). The silicone rubber in the SRD has previously been used to model tissue when evaluating the performance of tactile piezoelectric sensors (Eklund et al, 1999;Jalkanen et al, 2006;Astrand et al, 2013), as well as to model the elastic properties of human skin (Passot and Cabodevila, 2011;Kauer et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber

Jonsson

Lindahl

Andersson

2020

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Purpose The aim of the study was to show that a new method, using a look-up table technique, can be used to detect the presence and position of an inclusion embedded in a tissue-like material. Due to the time-consuming nature of the finite element (FE) method or FEM, real-time applications involving FEM as part of a control loop, are traditionally limited to slowly varying systems. By using a simplified two-dimensional FE model and a look-up table, we show by simulations and experiments that it is possible to achieve reasonable computational times in a tactile resonance sensor application. Design/methodology/approach A piezoelectric disk was placed in the center of a silicone rubber disk (SRD) with viscoelastic properties, where it acted as both sensor and actuator and dissipated radial acoustic waves into the silicone. The look-up table was constructed by calculating the radial Lamb wave transition frequencies in the impedance frequency response of the sensor while varying the position of an inclusion. A position-matching algorithm was developed that matched measured and calculated Lamb wave transitions and thereby identified the presence and position of an inclusion. Findings In an experiment, the position of a hard inclusion was determined by measuring the Lamb transition frequencies of the first radial resonance in two SRDs. The result of the matching algorithm for Disk 1 was that the matched position was less than 3% from the expected value. For Disk 2, the matching algorithm erroneously reported two false positions before reporting a position that was less than 5% from the expected value. An explanation for this discrepancy is presented. In a verifying experiment, the algorithm identified the condition with no inclusion present. Originality/value The approach outlined in this work, adds to the prospect of developing time-sensitive diagnostic instruments. This approach has the potential to provide a powerful technique to quickly present spatial information on detected tumors.

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Section: Methodsmentioning

confidence: 99%

Section: Boundary Value Conditions Of the Piezoelectric Sensor And Srd With Inclusionmentioning

confidence: 99%

Section: Hyper-elastic Compensating Function U(v )mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber

Jonsson

Lindahl

Andersson

2020

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Soft hybrid intrinsically motile robot for wireless small bowel enteroscopy

et al. 2022

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Background Difficulties in establishing diagnosis of small bowel (SB) disorders, prevented their effective treatment. This problem was largely resolved by wireless capsule endoscopy (WCE), which has since become the first line investigation for suspected SB disorders. Several types of WCE pills are now used in clinical practice, despite their limitations and complications. WCE pills are large, rigid and immotile capsules. When swallowed, they provide SB enteroscopy downloaded to a data logger carried by the patient. Most of the complications of WCEs result from lack of intrinsic locomotion: incomplete examination, capsule retention and impaction within strictures. In addition, the rigid nature and size of current generation of WCE pills is accompanied by 0.1% inability to swallow the pill by patients with normal esophageal motility. Methods The aim of this communication is to describe the initial prototype, P1, which is thinner and slightly longer than the current generation of WCEs. In addition, it exhibits intrinsic active locomotion, produced by vibrating silicon legs. These generate a controlled-skid locomotion on the small bowel mucosal surface, rendered slippery by surface mucus and intraluminal surfactant bile salts. We demonstrate the mechanism responsible for the active locomotion of P1, which we consider translatable into a working prototype, suitable for further R&D for eventual clinical translation. Results The shape and attachment of the rubber vibrating legs to vibrating actuators, have been designed specifically to produce a tight clockwise circular motion. When inserted inside a circular tube in vitro of equivalent diameter to human small intestine, the intrinsic circular clockwise motion of P1 translates into a linear locomotion by the constraints imposed by the surrounding circular walls of SB and rest of the gastrointestinal tract. This design ensures device stability during transit, essential for imaging and targeting lesions encountered during the enteroscopy. We preformed two experiments: (i) transit of P1 through a phantom consisting of a segment of PVC tube placed on a horizontal surface and (ii) transit through a transparent slippery nylon sleeve insufflated with air. In the PVC tube, its transit rate averages 15.6 mm/s, which is too fast for endoscopy: whereas inside the very slippery nylon sleeve insufflated with air, the average transit rate of P1 is reduced to 5.9 mm/s, i.e., ideal for inspection endoscopy. Conclusions These in-vitro experiments indicate that the P1 hybrid soft robot prototype has the potential specifically for clinical translation for SB enteroscopy.

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A simulation study on expansion of a small intestine model reactor

Zhang

Xiao

et al. 2022

Chemical Engineering Research and Design

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Modeling the high-frequency complex modulus of silicone rubber using standing lamb waves and an inverse finite element method

Cited by 4 publications

References 28 publications

Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber

Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber

Soft hybrid intrinsically motile robot for wireless small bowel enteroscopy

A simulation study on expansion of a small intestine model reactor

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