Revolutionizing On-Skin Prototyping with the SkinLink Toolkit

By Dr. Noopur JainReviewed by Susha Cheriyedath, M.Sc.Nov 5 2024

In a recent study, researchers have introduced a toolkit and workflow inspired by special effects (SFX) makeup techniques to create adaptable, reconfigurable on-skin prototypes. This approach supports adaptable, user-centered prototyping directly on the body, enhancing flexibility in wearable sensor design.

Background

Human skin, with its soft, adaptable, and highly textured surface, presents an ideal platform for integrating wearable technologies that enable seamless, touch-based interactions within easy reach. Recent advancements in on-skin technology have spurred the development of ultra-flexible devices through diverse fabrication methods, including inkjet and screen printing, water transfer techniques, lamination, and even free-hand painting.

While these methods allow for customized designs tailored to specific areas of the body, most devices become rigid after fabrication, which limits flexibility during prototyping stages. Additionally, the materials commonly used often lack the stretch and elasticity needed to accommodate the dynamic, uneven nature of the skin.

To address these limitations, the SkinLink toolkit was developed, offering a modular approach to flexible on-skin prototyping. SkinLink includes adaptable printed circuit boards (FPCBs) and stretchable connectors engineered to conform to various body contours and endure movement.

These components support the creation of reconfigurable on-skin interfaces, enabling dynamic adaptability in wearable design. A usability study demonstrates how SkinLink enhances both the flexibility and comfort of on-skin devices, making it a practical toolkit for both seasoned designers and novice creators.

Research Overview

The study was conducted in three main stages: a brief 5-minute introduction, a 60-minute circuit fabrication session, and a 25-minute post-study survey and interview. In the initial phase, participants received an overview of on-skin prototyping principles and an introduction to the specific circuit components they would use.

During the fabrication session, participants created two circuits with identical functionalities, utilizing modules from two different toolkits. Each circuit was applied to the participants' chosen body areas. To reduce bias and gather well-rounded feedback, a within-subject design was used, with the order of toolkit usage counterbalanced among participants.

In the post-study phase, a semi-structured interview gathered insights on the fabrication process, comfort and wearability, aesthetic flexibility, and suggestions for improvement. Two researchers facilitated these sessions, capturing video and audio for subsequent analysis.

Each toolkit contained the essential materials for building functional circuits. For the SkinLink setup, the toolkit included an Inertial Measurement Unit (IMU) sensor, a 4-LED module, microcontroller units, and four types of trace modules in varying lengths, along with prosthetic silicone for secure adhesion to the skin. In comparison, the SkinKit toolkit offered customized PCB modules, flexible trace materials, and double-sided tape for skin application.

Fourteen participants (10 females and 4 males, ages 19-28) were selected based on demographic surveys, with backgrounds in STEM or design fields. Quantitative data included metrics on time spent, the number of modules used, and skin surface area coverage. Ease of fabrication and wearability were assessed using a 7-point Likert scale survey, with results analyzed through the Wilcoxon signed-rank test. Qualitative data from interviews were transcribed and thematically coded to identify key patterns and insights.

Results and Discussion

The study results encompass both quantitative data—such as fabrication time, component usage, and skin coverage—and qualitative feedback from participant interviews.

The findings indicated that SkinLink prototypes required fewer wire modules (2.14 on average) compared to SkinKit (5.21 on average), suggesting a more streamlined design for SkinLink. Although both toolkits allowed rapid fabrication (under 13 minutes), SkinLink’s silicone-based adhesion process necessitated additional solidifying time; however, this did not substantially increase total fabrication time relative to SkinKit.

Participants generally favored SkinLink’s compact form, highlighting its smaller surface area and stretchable, flexible trace modules, which allowed comfortable placement on body areas with dynamic movement, such as wrists and fingers. Conversely, SkinKit’s rigid modules and larger footprint were more suited to broader, flatter body areas, with participants noting limitations in its adaptability to contours and movements.

Feedback on comfort showed that SkinLink’s smaller, flexible traces minimized discomfort, adapting smoothly to the skin and remaining nearly unnoticeable during wear. In contrast, SkinKit’s larger adhesive areas were noted to be less comfortable, particularly during extended wear periods.

Aesthetically, SkinLink was well-received for its metallic, jewelry-like appearance, lending a futuristic style that many participants appreciated. Suggestions for improvement included introducing color-coded or width-varied traces to facilitate easier customization. On the topic of social wearability, several participants expressed willingness to use either toolkit in public if it proved practical.

Overall, the study confirmed SkinLink as a more adaptable on-skin prototyping solution, effectively balancing fabrication ease with comfort, aesthetics, and flexibility for diverse application areas.

Conclusion

In summary, SkinLink brings a fresh, creative approach to building on-skin interfaces, inspired by prosthetic makeup techniques for secure, adaptable wear. With flexible traces and modular circuits that mold comfortably to the body, this toolkit makes prototyping easy and customizable without losing functionality.

SkinLink’s design invites creative exploration, allowing users to personalize their on-skin devices for both comfort and style. Through collaborations with makeup artists and wearable designers, SkinLink shows real promise for sparking interest and involvement from a wider community. By opening up wearable tech to diverse perspectives, it encourages more inclusive and expressive designs in fields like UbiComp and HCI.

Journal Reference

Ku P.S., Huang K., et al. (2023). SkinLink: On-body Construction and Prototyping of Reconfigurable Epidermal Interfaces. Proceedings of the ACM on Interactives, Mobile, Wearable and Ubiquitous Technologies,7, 2. DOI: 10.1145/3596241, https://dl.acm.org/doi/10.1145/3596241