# Mechanical and Thermo-Regulative Investigations on Additively Manufactured Backpack Pads

## TL;DR

This study compares different additively manufactured backpack pad designs to improve thermoregulation and comfort during physical activities.

## Contribution

The study introduces a sensor system and evaluates additively manufactured lattice structures for backpack pads.

## Key findings

- Additively manufactured pads showed significant advantages in temperature and humidity management.
- The customized sensor system revealed that damping-improved back plate design had no significant effect.
- Five lattice structures were tested alongside a commercial pad using biomechanical and standardized tests.

## Abstract

Backpacks play a pivotal role in facilitating the transportation of essential items, particularly within the realm of physical activities. In demanding physical environments such as mountain sports, effective thermoregulation, pressure absorption, and distribution become paramount due to the repetitive interaction between the athlete’s back and the corresponding area of the backpack. Given that the backpack pads serve as a crucial component of this system, acting as the intermediary layer between the human body and the backpack itself, this study delves into the mechanical and thermoregulatory properties of these components. Specifically, it compares a commercially available pad configuration with five lattice structures manufactured using additive manufacturing techniques. These methods include Large-Volume Filament printing, Multi-Jet Fusion, High-Speed Laser Sintering, and Laser Sintering, with an additional post-processing step—smoothening—for the Multi-Jet Fusion pads. All pads are evaluated on both standardized test protocols regarding mechanics, surface roughness, and humidity as well as a biomechanical setup. For continuous measurement during biomechanical testing, a sensor system including pressure, humidity, and temperature sensors is developed. In addition, a thermal camera was used to measure surface temperature at the back. Throughout the biomechanical testing, 20 male athletes performed a 15 min treadmill walk at 5 km/h and an incline of 6° with all pad configurations, wearing a commercially available backpack with an additional 8 kg of mass. The results revealed significant preferences regarding temperature and humidity uptake, backed up by the standardized test procedures. Furthermore, investigations with the customized sensor system show the irrelevance of the damping-improved back plate design. Overall, additively manufactured backpack pads can play a pivotal role in the thermoregulation and personalized design of backpack configurations.