Abstract
Background: This work is part of an ongoing study on the use of natural materials to provide low cost exoskeleton and orthopedic devices in general. An earlier work showed that fir, pine, oak and bamboo satisfied the requirements of the mid-stance of the Gait cycle which is about 10% of a person’s total weight. In reality, there are eight determinants of the gait cycle and they involve pelvic rotation and tilt, in addition to foot mechanics, knee mechanics and lateral displacement of pelvis. Furthermore, during walking, the peak vertical ground reaction force can rise up to 1.2 times the body weight. Therefore, any replacement exoskeleton material is expected to withstand this amount of compressive force and the rotational torques as well as possess excellent fracture toughness. Methods: The eight determinants of the gait cycle of normal walking were analyzed with along their consideration that during walking, the peak vertical ground reaction force can rise up to 1.2 times the body weight. The materials selection process utilized the Ashby’s procedure and consists of four steps, namely: translation, screening, ranking and documentation. Additional assessment of the fracture toughness and formability of the materials were carried out. Results: While all the natural materials satisfied the basic selection, process based on cost and weight, only oak and Moso bamboo fulfilled the additional requirement of strength and formability. Oak was however eliminated due to its characteristic low fracture toughness which means that it is unable to provide the weight bearing support in the stance phase. Conclusion: All the natural materials studied satisfied the cost and weight requirements for low-cost orthopedic devices. However, only Moso bamboo with its characteristic high fracture toughness and formability can comfortably replace duralumin in exoskeleton.
Highlights
Current exoskeletonsThis work presents a more comprehensive assessment of the use of natural materials in orthopedic application and it is a follow up on a previous paper which dealt with the use of low-cost material for exoskeletal application
While all the natural materials satisfied the basic selection, process based on cost and weight, only oak and Moso bamboo fulfilled the additional requirement of strength and formability
The design requirements for an exoskeleton and prosthetic are given in the Function-Constraints-Objectives-Free Variables (FCOFV) chart of Table A-1 [5]
Summary
Current exoskeletonsThis work presents a more comprehensive assessment of the use of natural materials in orthopedic application and it is a follow up on a previous paper which dealt with the use of low-cost material for exoskeletal application. For person’s living with gait and balance disorders, gait abnormality can limit quality of function and create barriers on activity performance and participation [2] This is significant for the lower extremity (LE) amputee, where the major limitation is often the difficulty with walking [2,3]. While prostheses are artificial devices used to replace missing body parts, exoskeletons work in parallel with the body to assist the user in their movements. Both devices are primarily used for rehabilitation purposes, Exoskeletons can be used as safety equipment.
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