P1045 Breast skin strain sensor array configurations
Dr. Michelle Norris, Dr. Amy Sanchez, Dr. Chris Mills, Professor Joanna Wakefield-Scurr
University of Portsmouth, Portsmouth, United Kingdom

Abstract

Introduction
    Silver et al. [1] reported that at 30% skin strain the skin enters a resistance zone, whilst at 60% skin strain the skin enters a failure zone. However, the ability to apply these thresholds is reliant on accurate breast skin strain measurements. Therefore, the purpose of this study was to compare four sensor array configurations, when calculating breast skin strain.

Methods
    Ten females gave written informed consent (breast sizes 32-34, D-G). Breast and torso motion data were recorded via an electromagnetic, 14-sensor array. Strain lines were defined within four configurations (Figure 1). Participants were then required to perform a range of everyday activities; standing, lifting, sweeping and walking on a treadmill.


Figure 1. Sensor array configurations.

Participants performed all activities in an unsupported condition, and then also in an everyday bra. Following this participants neutral breast position was recorded in a hot tub spa (37°C), for 6 seconds [4]. Breast skin strains were then calculated using,

Equation 1: Strain =

               

where L was defined as the average inter-sensor separation during any given activity and L0 was defined as the neutral (unloaded) inter-sensor separation during water submersion.

Results 
    In an unsupported condition peak breast skin strain ranged between 18 and 49 %, whilst in the supported condition peak breast skin strain ranged between -1 and 26 %. In both conditions sensor configurations displayed an increase in breast skin strain sensitivity as the number of sensors within the configuration increased (the 14-sensor array identified the largest peak breast skin strain and the 2-sensor array identified the smallest peak skin strain).  

Discussion
    When investigating the region and direction of breast skin strains in the unsupported condition, the 5-, 7- and 14-sensor arrays identified peak breast skin strains occurring in the upper region of the breast vertically. However, within the supported condition, the 5-, 7- and 14-sensor array configurations identified peak breast skin strains occurring in the lower region of the breast vertically.

Conclusions
    In an unsupported condition utilising a 5-, 7- or 14-sensor configuration will provide appropriate results regarding the region and direction of breast skin strain. Within a supported condition whilst a 7- or 14-sensor configuration produces similar peak breast skin strains, the medial-lateral region in which peak breast skin strain is located varies. 

Acknowledgements
M. Norris and A. Sanchez received funding for the current study from Hanes Brands Inc.

References
1. Silver F., et al. (2001). Skin Res Tech, 7(1) p18-23
2. Rajagopal, V., et al. (2008). Academ Radio, 15(11) p1425–1436
3. Haake S. and Scurr J. (2011). Sports Eng, 14(49) p49-56
4. Mills C., et al.(2016). J Biomech, 49(16) p4134-4137