Monika Kwacz

Static friction and adhesion in polymer-polymer microbearings

Abstract The starting process, i.e., transition from static to kinetic friction in polymer–polymer microbearings, was studied. Load, sliding speed and time of contact before starting were varied during the experiments. AFM studies of rubbing surfaces were performed and the real surfaces were brought into contact in computer simulations to evaluate the adhesive and frictional interactions. Correlation between observed static friction force, adhesive force and calculated friction force characteristics vs. time was found.

Reconstruction of the 3D Geometry of the Ossicular Chain Based on Micro-CT Imaging

Modelling of the sound transmission process from the externai ear canal through the middle ear structures to the cochlea is often performed using the finite element method. This requires knowledge of the geometry of the object being modelled. The paper shows the results of reconstruction of the 3D geometry of the ossicular chain. The micro-CT images of a cadaver’s temporal bone were used to carry out the reconstruction process. The obtained geometry may be used not only for modelling of the middle ear mechanics before and after ossicular replacement but also for production of anatomical middle ear prostheses, calculation of inertial properties of the ossicular bones or educating radiologist and otolaryngologist.

Comparison of round‐window membrane mechanics before and after experimental stapedotomy

Surgical intervention within the area of the middle ear always leads to alteration of conditions in its biomechanical system. This fact may provide an explanation for the lack of expected auditory outcome, although an apparently good anatomic outcome was obtained. In the case of stapedotomy, the majority of patients report lack of satisfactory results for frequencies above 2,000 Hz. The effect has not been experimentally investigated yet.

New chamber stapes prosthesis – A preliminary assessment of the functioning of the prototype

Piston-stapedotomy is the most common method for hearing restoration in patients with otosclerosis. In this study, we have experimentally examined a prototype of a new chamber stapes prosthesis. The prototype was implanted in a human cadaver temporal bone. The round window vibrations before and after implantation were measured for the acoustic signal (90 dB SPL, 0.8–8 kHz) in the external auditory canal. In comparison with a 0.4-mm piston prosthesis, the chamber prosthesis induced significantly higher vibration of the round window, especially for frequencies above 1.5 kHz. Based on the results, it can be surmised that stapedotomy with a chamber stapes prosthesis could provide better hearing results in comparison with the piston-stapedotomy.

Numerical Study of the PDMS Membrane Designed for New Chamber Stapes Prosthesis

New chamber stapes prosthesis (ChSP) is intended to restore hearing in patients with conductive hearing loss caused by otosclerosis. The proper selection of the membrane stiffness determines the effective prosthesis functioning. In this study, finite element (FE) model and simulation results of the poli-dy-methylo-siloxane (PDMS) membrane thickness are presented. The FE model was created using Abaqus 6.13 software. During simulations, the membrane thickness was adjusted so that its stiffness was similar to the stiffness of the normal stapes annular ligament. The simulation results allow to build a series of ChSP prototypes for preclinical experiments.

Biocompatible membrane of PDMS for the new chamber prosthesis stapes.

Stapes protheses are designed for patients with otosclerosis resulting immobilization or significant reduction of the stapes mobility. All currently used prostheses are called - piston prosthesis. However, its use to stimulate the cochlea is still imperfect. New chamber stapes prosthesis allows the perilymph excitation more effective than the piston prothesis. Moreover, the chamber prosthesis eliminates the common causes of piston-stapedotomy failures. The most important element of the new prosthesis is a flexible membrane. The membrane stiffness should be close to the stiffness of normal annular ligament. This work presents the process of selection of the membranes thickness and its manufacturing technology. Method A 3D model of the chamber stapes prosthesis was build using Autodesk Inventor 2015. The model was imported to Abacus 6.13 computing environment. During numerical simulations, displacements corresponding to applied loads were calculated and the membrane thickness was adjusted so that its stiffness was the same as the ligament stiffness (~ 120 N/m). The compliance ratios calculated from the load-displacement curves for the membrane and the annular ligament were verified using linear regression analysis. After determining the thickness, the manufacturing technology of the membrane was developed. Results The best similarity between the membranes and annular ligaments stiffness was achieved for PDMS membrane with the 0,15- mm thickness (similarity ratio R2=0,997752). In this work, the technological parameters of spin-coating process for membrane manufacture are also presented. Summary The proper functioning of the chamber stapes prosthesis requires the PDMS membrane with a thickness of 0,15 mm. The 0,15-mm membrane has the tiffness close to the stiffness of the normal annular ligament. Therefore, the chamber stapes prosthesis provides the perilymph stimulation at the level comparable to the healthy ear. New prosthesis is currently under pre-clinical investigation to optimize the shape of the inner chambers surface.

New mechatronic stabilographic device – design and software

This work presents design of a new stabilographic force platform and software dedicated to this device written in Java. The software provides a graphical user interface and easy analysis of the posturograph. The algorithm calculates the following parameters: total length of stabilogram, total and average distance from main position, average speed of center of pressure, percentage of measurements beyond the scope of stable sways, maximum sway in antero-posterior and medio-lateral surface, and total length of stabilogram in both planes.

The Effect of Stapedotomy on Round Window Membrane Motion – An Experimental Study

This paper presents the results of non-contact measurements of the human ear round window (RW) membrane motion in freshly harvested human cadaver temporal bone specimens. A PSV 400 Scanning Laser Vibrometer system (Polytec, Waldbronn, Germany) was used to determine the effect of stapedotomy on the sound-induced displacement amplitude of the RW membrane. The vibration patterns was measured in the frequency range 0.4-10 kHz in four specimens with air conduction stimulation at 90 dB SPL applied to the external auditory canal. It was shown that the vibration amplitude of the RW membrane after stapes piston prosthesis implantation, in comparison with a physiological specimen was reduced several times. The motion of the RW membrane can be used to determine the cochlear stimulation for evaluation middle ear ossicle reconstruction, especially in the case of otosclerosis surgery.

Transmission of the Acoustic Signal through the Middle Ear – An Experimental Study

The transmission of the acoustic signal through the middle ear structures was determined on the basis broad-band measurements (400 Hz to 10 kHz) of the stapes, the round window and the Teflon piston stapes prosthesis displacements. The measurements were made in 4 fresh cadaver temporal bones with AC stimulation at 90 dB SPL applied to the external auditory canal. Two conditions in the same specimen were measured: the physiologial and the implanted state. A PSV 400 Scanning Laser Doppler Vibrometer system (Polytec GmbH, Waldbronn, Germany) was used to determine the effect of the Teflon piston stapes prosthesis implantation on transmission of the acoustic signal through the middle ear. It was shown that the cochlear stimulation after stapes piston prosthesis implantation, in comparison with a physiological specimen was reduced several times.