DEVELOPMENT OF A VIRTUAL HUMAN HAND MODEL FOR ERGONOMIC PRODUCT DESIGN

Velik del ročnih opravil je še vedno opravljen s pomočjo ročnih orodij. Pravilna zasnova ročaja orodja je tako lahko ključnega pomena za preprečevanje obolenj. Obstoječe metode načrtovanja upoštevajo valjaste ročaje in podajajo smernice za določitev optimalnih premerov za povečanje zmogljivosti in zviševanje udobja ob zmanjševanju možnosti za nastanek akutnih in kumulativnih travmatičnih obolenj. Oblika ročaja in materiali ročaja doslej niso bili podrobneje raziskani, kar bi imelo vpliv na izboljšanje ergonomije izdelka. Za premostitev omejitev glede določitve oblike ročaja, smo razvili anatomsko natančen statični virtualni model človeške roke v optimalnem krepkem oprijemu za neposredno oblikovanje ročaja orodja, ki temelji na interdisciplinarnem pristopu na osnovi medicinskega slikanja. Da bi odpravili omejitve glede pravilne določitve materiala ročaja orodja, smo uporabili metodo končnih elementov za simulacijo človeškega prsta ob oprijemu ročaja iz različnih materialov. Rezultati so pokazali, da ročaj orodja, ki temelji na razvitem virtualnem modelu človeške roke, zagotavlja bistveno večjo kontaktno površino in udobje v primerjavi s cilindričnim ročajem. Z večjo kontaktno površino in anatomsko obliko ročaja je mogoče preprečiti prekomerne deformacije mehkega tkiva in s tem prekomerne obremenitve na roko. Numerični izračuni so pokazali, da običajni materiali ročajev orodij ne zmanjšujejo kontaktnega tlaka ob oprijemu, predlagane hiper-elastične pene, ki upoštevajo nelinearno mehansko obnašanje mehkega tkiva pa lahko znatno zmanjšajo kontaktni tlak in hkrati ohranijo zadostno stopnjo stabilnosti. Rezultati tako potrjujejo domnevo, da lahko pravilna oblika in material ročaja orodja povečata učinkovitost in udobje in s tem zmanjšata tveganje za nastanek akutnih in kumulativnih travmatičnih obolenj.A significant part of manual work is still done using hand-tools. Therefore, an ergonomic design of a tool-handle might be crucial for preventing upper-extremity musculoskeletal disorders. Current design methods consider cylindrical handles and provide guidelines for determining optimal diameters to increase performance, comfort and thus minimizing the risk of acute and cumulative traumatic disorders. However, the shape of the handle and the handle’s materials have not been investigated in detail yet, which could additionally improve the handles’ ergonomics. In order to overcome the limitations of correct shape determination, we have developed an anatomically accurate static virtual human-hand model in its optimal power grasp posture for direct tool-handle modelling based on interdisciplinary methods using medical imaging. To overcome the limitations regarding the correct tool-handle material determination, we have utilized a finite-element method for simulating human fingertip whilst grasping different tool-handle materials. The results have shown that the tool-handle based on the developed virtual human-hand model provides significantly higher contact area and comfort rating compared to the cylindrical handles. With higher contact area and anatomical shape of the handle, extensive deformation of the soft tissue can be avoided, thus preventing excessive load on the hand. Numerical tests have shown that conventional tool-handle materials do not lower the contact pressure. The proposed hyper-elastic foam materials, which take into account the non-linear mechanical behavior of fingertip, can lower the contact pressure significantly whilst maintaining sufficient rate of stability. Results thus support the thesis that correct shape and material determination of a tool-handle can increase the performance and comfort and thus lower the risk of acute and cumulative trauma disorders

DESIGN AND ERGONOMIC ASPECTS OF PHOTOGRAPHIC CAMERA DEVELOPMENT

Fotoaparat je naprava za zajemanje svetlobe. Od njenega izuma, do danes se je na osnovi stalnega razvoja, nove tehnike in tehnologije precej spremenila. Zraven zagotavljanja glavne funkcije je potrebno, da razvojni inženir oblikuje fotoaparat po principih industrijskega oblikovanja in ergonomije. Z upoštevanjem teoretičnih in praktičnih priporočil ter na osnovi antropometričnih tabel je mogoče doseči obliko, ki bo uporabnikom vizualno všeč ter bo omogočala enostavno in preprosto uporabo z malo utrujanja in brez poškodb uporabnika. V kolikor so principi industrijskega oblikovaja in ergonomije ustrezno zajeti v razvojni fazi, se ustvari dodatna vrednost fotoaparata, ki izboljša konkurenčnost izdelka na tržišču.A camera is a device for capturing light. From its invention till today it is under continuous development and new techniques and technologies have changed it considerably. Besides providing the main function, it is necessary to use the principles of industrial design and ergonomics. With theoretical and practical recommendations and anthropometrics a design can be achieved, which will provoke visual likeness and will allow easy use with little fatigue and without injury to the user. If these principles are adequately covered in the development phase, additional value is created, which improves the competitiveness of the camera on the market

Odprtokodna programska oprema za medicinske slike: študija primera na podlagi interdisciplinarne inovativne zasnove izdelka

Namen: V zadnjem času je bilo razvitih precej celovitih rešitev odprtokodne programske opreme za medicinske slike, ki ponujajo zmogljiva orodja za slikovno upravljanje, vizualizacijo, skladiščenje in analizo. Namen članka je predstaviti odprtokodno programsko opremo za delo z medicinskimi slikami in njene značilnosti ter jo primerjati s komercialnimi rešitvami. Metode: Predstavljen je primer razvoja optimalne velikosti in oblike ročaja ročnega orodja s pomočjo brezplačne odprtokodne programske opreme \u273D Slicer\u27. Večina avtorjev priporoča valjasto oblikovanost ročajev, da bi povečali udobje in učinkovitost uporabnika ter preprečili kumulativna travmatična obolenja, vendar optimalna oblika ročaja še ni bila ugotovljena. Namen raziskaveje predstaviti metode, s katerimi je mogoče pridobiti obliko ročaja v optimalni drži roke za krepki oprijem s čim bolj optimalno porazdelitvijo pritiska na mehka tkiva. Uporabili smo magnetno resonančno preiskavo in individualno izdelan kalup, ki je ohranjal optimalno držo roke med preiskavo. Program \u273D Slicer\u27 je bil uporabljen za segmentacijo in 3D rekonstrukcijo na osnovi MR slik. 3D model roke je bil nato \u27izvožen\u27 v komercialni program za računalniško podprto konstruiranje optimalnega ročaja orodja. Rezultati: Meritve premerov na 3D rekonstrukciji so pokazale, da so bili položaji zadržani z le majhnimi odstopanji, kar maksimizira največjo silo kontrakcije prstov. Tako oblikovan optimalni ročaj zagotavlja 25 % večjo kontaktno površino v primerjavi z optimalnim valjastim ročajem in s tem zmanjšuje tudi kontaktne tlake, kar povečuje učinkovitost in udobje ter (zelo verjetno) preprečuje kumulativna travmatična obolenja. Zaključki: Prikazan primer potrjuje ustreznost odprtokodne programske opreme za medicinske slike kot (večinoma) brezplačno in učinkovito orodje, podobno kot (neredko drage) druge komercialne rešitve

Numerical analysis of a transtibial prosthesis socket using 3D-Printed Bio-Based PLA

Lower-limb prosthesis design and manufacturing still rely mostly on the workshop process of trial-and-error using expensive unrecyclable composite materials, resulting in time-consuming, material-wasting, and, ultimately, expensive prostheses. Therefore, we investigated the possibility of utilizing Fused Deposition Modeling 3D-printing technology with inexpensive bio-based and bio-degradable Polylactic Acid (PLA) material for prosthesis socket development and manufacturing. The safety and stability of the proposed 3D-printed PLA socket were analyzed using a recently developed generic transtibial numeric model, with boundary conditions of donning and newly developed realistic gait cycle phases of a heel strike and forefoot loading according to ISO 10328. The material properties of the 3D-printed PLA were determined using uniaxial tensile and compression tests on transverse and longitudinal samples. Numerical simulations with all boundary conditions were performed for the 3D-printed PLA and traditional polystyrene check and definitive composite socket. The results showed that the 3D-printed PLA socket withstands the occurring von-Mises stresses of 5.4 MPa and 10.8 MPa under heel strike and push-off gait conditions, respectively. Furthermore, the maximum deformations observed in the 3D-printed PLA socket of 0.74 mm and 2.66 mm were similar to the check socket deformations of 0.67 mm and 2.52 mm during heel strike and push-off, respectively, hence providing the same stability for the amputees. We have shown that an inexpensive, bio-based, and bio-degradable PLA material can be considered for manufacturing the lower-limb prosthesis, resulting in an environmentally friendly and inexpensive solution

Development of a Generic Numerical Transtibial Model for Limb–Prosthesis System Evaluation

The well-established finite element method (FEM) has been used successfully to evaluate and develop medical devices for lower-limb prosthetics over recent decades. Most numerical models are based on a specific 3D geometry, which, although allowing for an accurate analysis of a specific case, may differ significantly from the target group that is often geometrically closer to the average residual limb. In order to address this issue, a generic numerical transtibial model was developed with the corresponding definitive socket and silicone liner. Three load cases were performed to analyse the applicability of the model: donning, single-leg stance, and the static P5 test according to ISO 10328. While the first two cases were used commonly in previous studies, the ISO test was only used in physical tests and not in a numerical environment. The results of the simulations in terms of contact pressure, as well as the relative deformation of the socket, fit into the range reported in the literature for similar boundary conditions, thus verifying the model in biomechanical terms. The generic transtibial model serves as a numerical tool for the relative comparison of different socket-liner designs prior to the fabrication, providing insights into results that are otherwise difficult to obtain

Influence of Product Interface Material Stiffness on Human Tactile Perception during a Grasping Task

When considering product handle ergonomics, authors have focused on product handle sizes and shapes, while handle materials have been largely ignored. Authors have shown that handles coated with rubber foam were more comfortable than stiff handles. However, they did not provide detailed material properties, nor did they investigate different stiffnesses and their impact on tactile perception during grasping. Therefore, in this article, we investigated the influence of product interface material stiffness using a common wood sawing task with a saw handle made of hard plastic and 3D-printed deformable material with different stiffnesses. The results showed that user tactile perception can be improved significantly where the 3D-printed cellular density, and, hence material stiffness, has a significant influence on the resulting tactile perception. However, results have shown that the material stiffness must be determined appropriately to maintain the stability of the products in hands. The results also suggest that the product interface material had a greater influence on the reported overall comfort rating than the product handle shape in the sawing task

Influence of Product Interface Material Stiffness on Human Tactile Perception during a Grasping Task

When considering product handle ergonomics, authors have focused on product handle sizes and shapes, while handle materials have been largely ignored. Authors have shown that handles coated with rubber foam were more comfortable than stiff handles. However, they did not provide detailed material properties, nor did they investigate different stiffnesses and their impact on tactile perception during grasping. Therefore, in this article, we investigated the influence of product interface material stiffness using a common wood sawing task with a saw handle made of hard plastic and 3D-printed deformable material with different stiffnesses. The results showed that user tactile perception can be improved significantly where the 3D-printed cellular density, and, hence material stiffness, has a significant influence on the resulting tactile perception. However, results have shown that the material stiffness must be determined appropriately to maintain the stability of the products in hands. The results also suggest that the product interface material had a greater influence on the reported overall comfort rating than the product handle shape in the sawing task

Development, fabrication and mechanical characterisation of auxetic bicycle handlebar grip

The auxetic cellular structures are one of the most promising metamaterials for vibration damping and crash absorption applications. Therefore, their use in the bicycle handlebar grip was studied in this work. A preliminary computational design study was performed using various auxetic and non-auxetic geometries under four load cases, which can typically appear. The most representative geometries were then selected and fabricated using additive manufacturing. These geometries were then experimentally tested to validate the discrete and homogenised computational models. The homogenised computational model was then used to analyse the biomechanical behaviour of the handlebar grip. It was observed that handle grip made from auxetic cellular metamaterials reduce the high contact pressures, provide similar stability and hereby improve the handlebar ergonomics

Hybrid 3D Printing of Advanced Hydrogel-Based Wound Dressings with Tailorable Properties

Despite the extensive utilization of polysaccharide hydrogels in regenerative medicine, current fabrication methods fail to produce mechanically stable scaffolds using only hydrogels. The recently developed hybrid extrusion-based bioprinting process promises to resolve these current issues by facilitating the simultaneous printing of stiff thermoplastic polymers and softer hydrogels at different temperatures. Using layer-by-layer deposition, mechanically advantageous scaffolds can be produced by integrating the softer hydrogel matrix into a stiffer synthetic framework. This work demonstrates the fabrication of hybrid hydrogel-thermoplastic polymer scaffolds with tunable structural and chemical properties for applications in tissue engineering and regenerative medicine. Through an alternating deposition of polycaprolactone and alginate/carboxymethylcellulose gel strands, scaffolds with the desired architecture (e.g., filament thickness, pore size, macro-/microporosity), and rheological characteristics (e.g., swelling capacity, degradation rate, and wettability) were prepared. The hybrid fabrication approach allows the fine-tuning of wettability (approx. 50–75°), swelling (approx. 0–20× increased mass), degradability (approx. 2–30+ days), and mechanical strength (approx. 0.2–11 MPa) in the range between pure hydrogels and pure thermoplastic polymers, while providing a gradient of surface properties and good biocompatibility. The controlled degradability and permeability of the hydrogel component may also enable controlled drug delivery. Our work shows that the novel hybrid hydrogel-thermoplastic scaffolds with adjustable characteristics have immense potential for tissue engineering and can serve as templates for developing novel wound dressings