multi-purpose ergonomic backpack for high school students

background; musculoskeletal disorders (msds) are among the most prevalent pains which could be ignited via material handling. backpack wearers are among those who may carry heavy loads. since msds mainly originate in school-aged children, students (as the largest group of backpack wearers) are considered more important. the purpose of this study is to design a backpack based on minimization of shearing force. methods; at first the relevant patents were investigated at national and international levels. then the appropriate ones selected for optimizing. the main selection criterion was based on reduction of pressure on body. as an extra function we used a generator to produce electricity. the criterion for electricity generator selection was: 1) small dimension, 2) low weight, and 3) safe voltage. results; a suspending system used to eliminate shearing forces. since a wearing backpack student is under the shearing force caused by walking, a spring system was used as a reducing device for shearing force. physical spring calculation revealed that springs with stiffness coefficient equal to 588 was appropriate. conclusion; in comparison with existing designs, suggested backpack design can reduce forces on upper limb during handling the backpack.