Smart polymer implants as an emerging technology for treating airway collapse in obstructive sleep apnea: a pilot (proof of concept) study.

STUDY OBJECTIVES: To assess the use of a novel magnetic polymer implant in reversing airway collapse and identify potential anatomical targets for airway implant surgery in an in vivo porcine model. METHODS: Target sites of airway collapse were genioglossus muscle, hyoid bone, and middle constrictor muscle. Magnetic polymer implants were sutured to these sites, and external magnetic forces, through magnets with pull forces rated at 102 kg and 294 kg, were applied at the skin. The resultant airway movement was assessed via nasendoscopy. Pharyngeal plexus branches to the middle constrictor muscle were stimulated at 0.5 mA, 1.0 mA, and 2.0 mA and airway movement assessed via nasendoscopy. RESULTS: At the genioglossus muscles, large magnetic forces were required to produce airway movement. At the hyoid bone, anterior movement of the airway was noted when using a 294 kg rated magnet. At the middle constrictor muscle, an anterolateral (or rotatory) pattern of airway movement was noted when using the same magnet. Stimulation of pharyngeal plexus branches to the middle constrictor revealed contraction and increasing rigidity of the lateral walls of the airway as stimulation amplitude increased. The resultant effect was prevention of collapse as opposed to typical airway dilation, a previously unidentified pattern of airway movement. CONCLUSIONS: Surgically implanted smart polymers are an emerging technology showing promise in the treatment of airway collapse in obstructive sleep apnea. Future research should investigate their biomechanical role as an adjunct to treatment of airway collapse through nerve stimulation.

Modeling the upper airway: A precursor to personalized surgical interventions for the treatment of sleep apnea.

An accurate benchtop model was developed to mimic the different forms of human upper airway collapse in adult sleep apnea patients. This was done via modeling the airway through digital imaging. Airway representative models were then produced in two steps via a customized pneumatic extrusion 3D printing system. This allowed the pressure of collapse and planes of collapse to be manipulated to accurately represent those seen in sleep apnea patients. The pressure flow relationships of the collapsible airways were then studied by inserting the collapsible airways into a module that allowed the chamber pressure (Pc ) around the airways to be increased in order to cause collapse. Airways collapsed at physiologically relevant pressures (5.32-9.58 cmH2 O). Nickel and iron magnetic polymers were then printed into the airway in order to investigate the altering of the airway collapse. The introduction of the nickel and iron magnetic polymers increased the pressure of collapse substantially (7.38-17.51 cmH2 O). Finally, the force produced by the interaction of the magnetic polymer and the magnetic module was studied by measuring a sample of the magnetic airways. The peak force in (48.59-163.34 cN) and the distance over which the forces initially registered (6.8-9.7 mm) were measured using a force transducer. This data set may be used to inform future treatment of sleep apnea, specifically the production of an implantable polymer for surgical intervention.

3D hybrid printing platform for auricular cartilage reconstruction.

As scaffolds approach dimensions that are of clinical relevance, mechanical integrity and distribution becomes an important factor to the overall success of the implant. Hydrogels often lack the structural integrity and mechanical properties for use in vivo or handling. The inclusion of a structural support during the printing process, referred to as hybrid printing, allows the implant to retain structure and protect cells during maturation without needing to compromise its biological performance. In this study, scaffolds for the purpose of auricular cartilage reconstruction were evaluated via a hybrid printing approach using methacrylated Gelatin (GelMA) and Hyaluronic acid (HAMA) as the cell-laden hydrogel, Polycaprolactone (PCL) as structural support and Lutrol F-127 as sacrificial material. Furthermore, printing parameters such as nozzle diameter, strand spacing and filament orientation scaffolds were investigated. Compression and bending tests showed that increasing nozzle sizes decrease the compressive modulus of printed scaffolds, with up to 82% decrease in modulus when comparing between a 400 µm and 200 µm sized nozzle tip at the same strand spacing. On the contrary, strand spacing and orientation influences mainly the bending modulus due to the greater porosity and changes in pore size area. Using a 400 µm sized nozzle, scaffolds fabricated have a measured compression and bending modulus in the range similar to the native cartilage. The viability and proliferation of human mesenchymal stem cells delivered within the bioink was not affected by the printing process. Using results obtained from mechanical testing, a scaffold with matching mechanical properties across six distinct regions mimicking the human auricular cartilage can be completed in one single print process. The use of PCL and GelMA-HAMA as structural support and cell-laden hydrogel respectively are an excellent combination to provide tailored mechanical integrity, while maintaining porosity and protection to cells during differentiation.

Knitted Carbon-Nanotube-Sheath/Spandex-Core Elastomeric Yarns for Artificial Muscles and Strain Sensing.

Highly stretchable, actuatable, electrically conductive knitted textiles based on Spandex (SPX)/CNT (carbon nanotube) composite yarns were prepared by an integrated knitting procedure. SPX filaments were continuously wrapped with CNT aerogel sheets and supplied directly to an interlocking circular knitting machine to form three-dimensional electrically conductive and stretchable textiles. By adjusting the SPX/CNT feed ratio, the fabric electrical conductivities could be tailored in the range of 870 to 7092 S/m. The electrical conductivity depended on tensile strain, with a linear and largely hysteresis-free resistance change occurring on loading and unloading between 0% and 80% strain. Electrothermal heating of the stretched fabric caused large tensile contractions of up to 33% and generated a gravimetric mechanical work capacity during contraction of up to 0.64 kJ/kg and a maximum specific power output of 1.28 kW/kg, which far exceeds that of mammalian skeletal muscle. The knitted textile provides the combination of strain sensing and the ability to control dimensions required for smart clothing that simultaneously monitors the wearer's movements and adjusts the garment fit or exerts forces or pressures on the wearer, according to needs. The developed processing method is scalable for the fabrication of industrial quantities of strain sensing and actuating smart textiles.

Knitted Strain Sensor Textiles of Highly Conductive All-Polymeric Fibers.

A scaled-up fiber wet-spinning production of electrically conductive and highly stretchable PU/PEDOT:PSS fibers is demonstrated for the first time. The PU/PEDOT:PSS fibers possess the mechanical properties appropriate for knitting various textile structures. The knitted textiles exhibit strain sensing properties that were dependent upon the number of PU/PEDOT:PSS fibers used in knitting. The knitted textiles show sensitivity (as measured by the gauge factor) that increases with the number of PU/PEDOT:PSS fibers deployed. A highly stable sensor response was observed when four PU/PEDOT:PSS fibers were co-knitted with a commercial Spandex yarn. The knitted textile sensor can distinguish different magnitudes of applied strain with cyclically repeatable sensor responses at applied strains of up to 160%. When used in conjunction with a commercial wireless transmitter, the knitted textile responded well to the magnitude of bending deformations, demonstrating potential for remote strain sensing applications. The feasibility of an all-polymeric knitted textile wearable strain sensor was demonstrated in a knee sleeve prototype with application in personal training and rehabilitation following injury.