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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session A

Poster I16 - An Upper Body Physical Model for Bench Testing of Assistive Devices for Infants

Thursday, October 24, 2024

10:00 AM - 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Emily Kuo (she/her/hers)

Bioengineering Undergraduate Student
University of California, Riverside
Riverside, California, United States
Christian Macaluso (he/him/his)

Undergraduate Bioengineering Student
University of California, Riverside
Elk Grove, California, United States

Co-Author(s)

AG

Aryan Gowda

Bioengineering Undergraduate Student
University of California, Riverside
Riverside, California, United States
CR

Chris Rauch, n/a

Bioengineering Undergraduate Student
University of California, Riverside
Riverside, California, United States
IS

Ipsita Sahin, MS (she/her/hers)

PhD Student in Bioengineering
University of California, Riverside
Riverside, California, United States

Primary Investigator(s)

EK

Elena Kokkoni, PhD

Assistant Professor of Bioengineering
University of California, Riverside
Riverside, California, United States

Introduction: Infants with or at risk for motor impairments face difficulty initiating or controlling their movements. Assistive devices can be used to address this challenge. However, these devices must undergo rigorous bench-testing to ensure their safety and efficacy before being tested with infants. Conducting these tests requires the use of physical models that accurately represent the size, proportions, and other critical characteristics of an infant's body. Currently, available physical models are costly and/or may not fully represent all anatomical features of an infant's body, such as articulated joints with the proper range of motion. To address this gap, we aimed to design and build an infant physical model with these features in mind. Our model matches the 50th percentile of a 6-month old infant. Separate body segments were designed with the proper anthropometric characteristics using computer-aided design software. These parts were designed to be hollow so as to add stainless steel powder and adjust the weight of the body segments. Adjustments to the model were made as needed. A preliminary analysis of the range of motion of the model’s joints and other parameters were conducted to determine how closely our model matches the infant’s body. In the future, this physical model will be used for bench-testing of upper extremity wearable assistive technology developed in our lab.

Materials and

Methods: The initial phase of pediatric physical model development involved gathering precise, anthropometric measurements of an average six-month-old infant from osteology textbooks, medical journals, and CDC resources. We obtained information on the size and weight of the torso, upper arm, forearm, and hand segments, as well as the shoulder and wrist joints. These measurements informed the 3D modeling process using Solidworks computer-aided design software, ensuring accurate representation of infant body anatomy and mechanics, including the design of the shoulder (ball-and-socket) and elbow (hinge) joints that would allow full range of motion. The model components were subsequently 3D-printed using polylactic acid (PLA) filament on an Ender 3 series pro printer. The settings used for each printed part were layer quality set to a height of 0.2 millimeters and width of 0.4 millimeters, wall thickness set at 0.8 millimeters and number of walls set to 3. Printer temperature remained at 200 degrees Celsius and the build temperature was at 40 degrees Celsius. Printing speed was maintained at 80 mm per second. Each part took from half an hour to 42 hours to complete depending on the size of the part being printed. The next step involved the assembly of the 3D-printed parts. To achieve the desired weight of each body segment, stainless steel powder was poured into the hollow crevices. Each joint (shoulder, elbow, and wrist) was independently assessed for its range of motion prior to model assembly.

Results, Conclusions, and Discussions: All segments and joints were successfully printed and assembled. The dimensions of each segment of the arm are as follows. The upper arm length is 13.4 centimeters and diameter is 4.6 centimeters. The forearm length is 8.68 centimeters and diameter is 4.1 centimeters. The shoulder joint is 6.27 centimeters in length which accounts for the extending piece used for mounting the arm to the torso. The wrist is 3.88 centimeters in length going from the forearm to the hand segment and the socket portion of the joint is 3 centimeters wide. The fingers vary in total length from 1.73 to 2.14 centimeters and segment diameter from 0.53 to 0.74 centimeters. The torso is 15.76 to 17.4 centimeters in width, 20 centimeters in length, and 12.9 centimeters in thickness. The weight of each arm came out to be approximately 580 grams and the torso to be about 2 kilograms. On the preliminary evaluation of the maximum passive range of motion; shoulder abduction/adduction angle came to be 140 degrees, elbow flexion/extension angle was 140 degrees, and wrist range of motion was 140 degrees (with greater palmar flexion at 90 degrees than extension at 50 degrees). Preliminary results indicate that the model accurately estimates the anatomy and biological motion of an infant of this age. However, several challenges were encountered during the design and fabrication of the model. For instance, the hand segment proved difficult due to the absence of standardized measurements for certain finger segments and palm curvature. The dimensions for these segments were approximated based on proportional growth coming from other data on one-year-old and six-month old infants. Furthermore, the 3D printing process caused deformations in the connective rings due to the heat from the nozzle melting small components. Assembling the finger segments was also problematic as the smaller parts were fragile and prone to breakage under pressure. The next phase of our project will focus on determining the center of mass for each body segment. Ultimately, we aim to develop a series of prototypes representing the infant body at different developmental stages, including models for 9- and 12-month-old infants.

Acknowledgements (Optional):