The biomechanics of blade shaving

Abstract

The shaving challenge represents a technical contradiction, whereby many of the requirements to improve hair removal efficacy can also result in increased damage to the surrounding skin. Poor-quality shaving can cause a significant inflammatory response of the skin, which may consequently lead to skin irritation and soreness. This study aims to explore and quantify the forces that act upon the skin and hair during the shave and suggests that careful management of these forces is essential in optimizing the shaving process. Various razor features are discussed and their impact on the resulting biomechanical forces is considered. Recent data are included comparing a basic low-tier disposable razor with a more technologically advanced premium system razor and show significant differences in both subjective shave attribute scores and resulting blood flux in the skin.

Facial hair shaving behavior and skin problems of shaved areas of males

“…Other investigations found that shaving problems were associated with shaving behaviors, such as rinsing off debris from razors, shaving direction, reshaving of an area, and frequency of changing razor blades. 8,9 Interestingly, none of those behaviors demonstrated a significant correlation with the problems reported in the current study.…”

Piezoresistive 3D graphene–PDMS spongy pressure sensors for IoT enabled wearables and smart products

“…A study conducted by Asakawa et al on 13 indivduals reported average loads of 0.5 N for tapping, 2.05 N for strectch, and 0.79 -1.18 N for sliding gestures (using index and thumb fingers) [36]. Furthermore, applications involving detection of force exerted by shaving blades on the face are typically ~ 2 N [37] and thus underscores the applicability of our sensors for such smart products.…”

“…Cyclic compressive loading tests (up to 70% compressive strain) conducted on the graphene-PDMS sponge revealed an average elastic modulus of ~56.7 kPa. Dynamic compressive uniaxial loading piezoresistive response tests (up to 8.23 N load) conducted on the sensor revealed force sensitivities of 0.3068 N -1 , 0.2389 N -1 and 0.2451 N -1 at 0.1, 0.2, and 0.3 Hz frequencies respectively with a linear behavior in the compressive load range ~ 0.42 -2.18 N. To demonstrate the repeatability of the fabrication process, electromechanical characterization experiments were conducted on four sensor samples and the average force sensitivities of the sensors was determined as 0.3470 ± 0.0794 N -1 at 0.2 Hz cyclic compressive loading with a linear response in the load range ~0.42 -2.18 N. The linear compressive load piezoresistive response characteristics in the aforementioned load range makes the sensors particularly relevant for applications in werable devices for measuring haptic force and consumer products like smart shavers capable of providing active feedback to users for comfortable shaving experience [36,37]. Furthermore, accelerated lifetime tests consisting of 1500 compressive loading cycles (at 3.90 N load) was conducted to demonstrate the long-term reliability and stability of the sensor.…”

Biomimetic Soft Polymer Microstructures and Piezoresistive Graphene MEMS Sensors Using Sacrificial Metal 3D Printing

“…Skin irritation arising from shaving is among the most common cosmetic complaints of males in the USA and Europe . Shaving discomfort correlates directly with forces (usually around 2 N on average) occurring during shaving, making it desirable to measure and quantify these forces. Electric shavers such as the Philips 9000 series used in this study are ideally required to operate with zero skin-cutter distance (SCD) to offer a close shave while minimizing skin irritation; however, direct measurement of the SCD is difficult and expensive, making it desirable to measure shaving forces from which the SCD can be inferred (and controlled, if needed) in real time.…”

“…Graphene was chosen as the piezoresistive sensing element in the PDMS microfluidic channels due to its high gauge factor and reliable piezoresistive behavior . The MEMS dome sensor was further integrated into a consumer product, namely, the Philips 9000 series personal shaver to demonstrate its feasibility in sensing shaving forces, with a view to potentially using the sensor data to take corrective action and reduce skin irritation …”