Benedito de Moraes Purquerio

A new design for an old concept of wheelchair pushrim

Purpose: Report on the development of an ergonomic manual wheelchair pushrim and evaluate the user’s perception of the quality of the device. Method: Based on anthropometric features and ergonomic concepts, a new wheelchair pushrim was designed, and a prototype was manufactured in polyurethane, using the rapid prototyping technique and serial production of parts by molding. The prototype was tested by a sample of wheelchair users, who rated the perceived quality of the device after testing both the new and conventional pushrims in a wheelchair propulsion experimental protocol. Results: The new ergonomic pushrim was found to be, in general, better than the conventional round tube pushrim. Specifically, experienced wheelchair users found the new wheelchair pushrim better in terms of easy and comfortable propulsion, braking and maneuvering of the wheelchair, and appearance. Conclusions: The new wheelchair pushrim provides a proper fit for the hands due to its ergonomic design and its polyurethane composition, making wheelchair propulsion easier and more comfortable than the conventional wheelchair pushrim. Assistive technology devices should be design based on ergonomic concepts that involve less effort and offer greater comfort for the user. Implications for Rehabilitation Manual wheelchair propulsion has been related with upper limb injuries that may potentially limit functionality. The conventional pushrim does not meet the need for a firm and stable grip, requiring further effort to hold the pushrim during manual propulsion that may cause discomfort, pain and contribute for developing upper limb injuries. In a relatively small sample of wheelchair users, this study shows that an ergonomically designed pushrim makes manual propulsion easier and more comfortable compared to the conventional pushrim.

Ceramic matrices applied to aerostatic porous journal bearings: material characterization and bearing modeling

This paper presents the development of an advanced ceramic material for manufacturing aerostatic porous bearing. The results show that there is homogeneous distribution of the pores in the alumina matrix by using different concentrations of the added component (sucrose). The average pore diameter remained around 0.14 µm and respective porosity around 28%, with small standard deviation. The mathematical model of the aerostatic porous bearing is presented, and numerical results indicate that the parameter related to porous medium (Г) strongly affects the resultant bearing load capacity and stiffness. Considering the experimental and numerical results, the porous matrix obtained with 40% of sucrose concentration is more suitable for the aerostatic porous bearing application in study.

Cartilage reconstruction using self-anchoring implant with functional gradient

This study presents an innovative and original biomaterial designed to substitute for articular cartilage and mimic its mechanical behavior, including elastic cushioning and the characteristics of fiber-reinforced gel. The material was composed of polyurethane and bioglass microfiber 45S5. It was designed to present a tribological surface to the cartilage of the tibial plateau, and to convert over a functional gradient to an osteointegrable region for self-anchorage to the subchondral bone. The biomaterial samples showed no toxicity and promoted cell spreading. Subsequent in vivo studies in rabbits demonstrated the formation of a rigid structure similar to bone trabeculae in the distal region of the tribological surface of the implant. The tribological surface of the proximal region showed a fibrocartilaginous tissue with highly vascularized chondrocytes, thus validating the proposed concept for the design of the implant incorporating a functional gradient and auto-stability.

Modified Reynolds Equation for Aerostatic Porous Radial Bearings With Quadratic Forchheimer Pressure-Flow Assumption

Aerostatic porous bearings are becoming important elements in precision machines due to their inherent characteristics. The mathematical modeling of such bearings depends on the pressure-flow assumptions that are adopted for the flow in the porous medium. In this work, one proposes a nondimensional modified Reynolds equations based on the quadratic Forchheimer assumption. In this quadratic approach, the nondimensional parameter Φ strongly affects the bearing load capacity, by defining the nonlinearity level of the system. For values of Φ>10, the results obtained with the modified Reynolds equation with quadratic Forchheimer assumption tend to those obtained with the linear Darcy model, thus showing that this is a more robust and global approach of the problem, and can be used for both pressure-flow assumptions (linear and quadratic). The threshold between linear and quadratic assumptions is numerically investigated for a bronze sintered porous bearing, and the effects of bearing geometry are discussed. Numerical results show that Φ strongly affects the bearing loading capacity and stiffness coefficients.

Compression tests of castor oil biopolymer

Many methods have been developed to test and evaluate the mechanical properties of the biopolymer from castor oil employed in implants and osteo-repositions, among other things. Most of the methods are performed under quasi-static and cyclic loads (creep and relaxation tests) and under high strain rate, uniaxial compression conditions. This paper presents and discusses the development and applicability of a simple load-application apparatus, devised to reduce shear and barrelling effects on specimens and allow for conventional strain around 45%. Besides contributing valuable information on the mechanical behavior of the castor oil polyurethane, the results of this research point to multiple biomedical applications for this material.

Bone response to porous alumina implants coated with bioactive materials, observed using different characterization techniques

Background Implants or implantable devices should integrate into the host tissue faster than fibrous capsule formation, in which the design of the interface is one of the biggest challenges. Generally, bioactive materials are not viable for load-bearing applications, so inert biomaterials are proposed. However, the surface must be modified through techniques such as coating with bioactive materials, roughness and sized pores. The aim of this research was to validate an approach for the evaluation of the tissue growth on implants of porous alumina coated with bioactive materials. Methods Porous alumina implants were coated with 45S5 Bioglass® (BG) and hydroxyapatite (HA) and implanted in rat tibiae for a period of 28 days. Ex vivo resections were performed to analyze osseointegration, along with histological analysis, Scanning Electron Microscopy with Energy Dispersive X-Ray spectroscopy (SEM-EDX) line scanning, radiography and biomechanical testing. Results Given that the process of implant integration needs with the bone tissue to be accelerated, it was then seen that BG acted to start the rapid integration, and HA acted to sustaining the process. Conclusions Inert materials coated with bioglass and HA present a potential for application as bone substitutes, preferably with pores of diameters between 100 μm and 400 μm and, restrict for smaller than 100 μm, because it prevents pores without organized tissue formation or vacant. Designed as functional gradient material, stand out for applications in bone tissue under load, where, being the porous surface responsible for the osseointegration and the inner material to bear and to transmit the loads.

Direct Manufacture of Hydroxyapatite Scaffolds Using Blue Laser

The study deals with the direct manufacturing of hydroxyapatite scaffolds using selective polymerization of the slurry liquid phase. The bovine hydroxyapatite has great similarity with the human bone structure, making it able for a direct connection with the bone tissues. This study aims to obtain scaffolds using a new technique of rapid prototyping, obtained by polymerization of acrylic resin (liquid phase of slurry) by ultraviolet light present in a range of the band spectrum emitted by the blue laser light. Sub-micrometer hydroxyapatite was obtained by the calcination and grinding of bovine bone in a vibratory mill. Mixtures of hydroxyapatite and resin were prototyped in three-dimensional pieces and sintered afterword and subjected to blue laser emission path directed in a CNC equipment. Grounded particles obtained in the grinding vibratory mill, with equivalent diameter of 0.35 microns, were reactive enough to compensate the low green densification bellow 50 vol%. Polymerization tests realized indicated that the incidence of the laser with fluency of 170 mW.s/mm2 promoted the curing of the 0.5 mm diameter pieces in depth about 0.5 mm, which allowed the prototyping of the scaffolds with sufficient mechanical strength for handling.

Prensa isostática de vasos gêmeos: projeto

Design and manufacturing of an isostatic press wetbag with two vessels of different volumetric capacities are presented. The isostatic press, widely applied in the forming of ceramic techniques since the beginning of the last century, is still an important laboratory equipment which is required when pressures are up to 500 MPa. The greatest difficulties of the researchers related to these equipments are in operation and maintenance. This paper presents the design of an isostatic press with two different vessels in terms of volumetric capacity, thus depending on the size of the samples in the process, making possible the selection of a suitable vessel or two vessels simultaneously. Hydrostatic pressure of 210 MPa was selected and designed two vessels of internal diameters of 95 mm and 55 mm with clover leaf and threaded lid locks, respectively. A compact, safe, economical and optimized maintenance equipment that accelerates the process and production of test specimens was obtained.

Development of gypsum powder and binder for 3D print rapid prototyping)

Formulation of gypsum powder and binder for use in 3D print prototype was developed. The 3D printing technique consists of the three-dimensional deposition of binders on successive layers of powder slices; the binder reacts with the powder and consolidates the two-dimensional format of each printed section, which added to subsequent slices consolidates the three-dimensional model. Although this model of three-dimensional printer is becoming popular mainly for its low cost, powder and binder are the greater obstacles due to their high cost. In this project formulations of powders, obtained by grinding the gypsum in alcoholic medium with binders and additives followed by agglomeration of fine particles of gypsum were developed. Formulations of binders based on the reaction of gypsum, considering the binding affinity and the operation of the print head were proposed and tested. The conditions of the agglomerated powder to the uniformity of the deposition layers and the minimum requirement of the binder for the operation of the print head were evaluated. Bar shaped specimens were produced on commercial 3D printing equipment and analyzed with respect to flexural strength, density and dimensional shape. Specimens from the powder were obtained with addition of 5 vol.% PVB and binder with 90 vol.% of distilled water and resistivity of 290 kΩ that showed an average flexural strength of 0.33 MPa, which was enough for initial handling, with simplified manufacture and a very economical cost.

A new walking aid with axillary support for children with cerebral palsy: electromyographic evaluation

Abstract Purpose: To present a new walking aid with axillary support (WAAS) for children with cerebral palsy (CP) and to investigate its impact on the lower limb muscles activation in the gait of children with CP. Method: Six children with spastic diparesis due to CP performed a straight line walking course in two situations: with and without using the WAAS. Each course was repeated three times for both situations, and electromyography (EMG) activity of quadriceps, hamstrings, tibialis anterior and gastrocnemius were recorded during all trials. Results: The use of WAAS significantly increased the EMG activity of the quadriceps and hamstrings during stance phase and tibialis anterior during swing phase, with no significant increase in gastrocnemius activation. Conclusion: The use of WAAS improved the synergism of lower limbs muscles of children with CP by reducing the coactivation of antagonistic muscles, especially during the swing phase of gait. Providing a walking aid with improved trunk stability may enable children with CP to improve muscular synergism and walking ability, thus favoring independent mobility, with possible gains in social participation and quality of life. Implications for Rehabilitation Children with cerebral palsy have problems with the development of normal gait, as a result of the reduced motor control and the impaired muscle synergism of the lower limbs. Standard walking aids do not provide proper trunk stability for this group of children. In a relatively small sample of children with cerebral palsy, a walking aid with axillary support was shown to be beneficial for the muscular synergism of the lower limbs during gait.