SweatSkin: Rapidly Prototyping Sweat-Sensing On-Skin Interface Based on Microfluidics
Sweat sensing affords monitoring essential bio-signals tailored for various well-being inspections. We present SweatSkin, the fabrication approach for customizable sweat-sensing on-skin interfaces. SweatSkin is unique in exploiting on-skin microfluidic channels to access bio-fluid secretes within the skin for personalized health monitoring. To lower the barrier to creating skin-conformable microfluidics capable of collecting and analyzing sweat, four fabrication methods utilizing accessible materials are proposed. Technical characterizations of paper- and polymer-based devices indicate that colorimetric analysis can effectively visualize sweat loss, chloride, glucose, and pH values. To support general to extreme sweating scenarios, we consulted five athletic experts on the SweatSkin devices' customization guidelines, application potential, and envisioned usages. The two-session fabrication workshop study with ten participants verified that the four fabrication methods are easy to learn and easy to make. Overall, SweatSkin is an extensible and user-friendly platform for designing and creating customizable on-skin sweat-sensing interfaces for UbiComp and HCI, affording ubiquitous personalized health sensing.
Publication:
SweatSkin: Rapidly Prototyping Sweat-Sensing On-Skin Interface Based on Microfluidics
Chi-Jung Lee, David Yang, Pin-Sung Ku, Hsin-Liu Cindy Kao
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies (IMWUT) 2024
Project Credits:
Hybrid Body Lab at Cornell University, directed by Cindy Hsin-Liu Kao
Research Team:
Chi-Jung Lee (Lead Researcher), David Yang, Pin-Sung Ku, Cindy Hsin-Liu Kao (Lab Director)
This project was supported by the National Science Foundation under Grant IIS-2047249.
The five-dimensional design space of SweatSkin.
We propose two form factors and, in total, four fabrication methods using different easily-accessible materials: (a) a paper-based device with wax (crayon) as a hydrophobic barrier, (b) a paper-based device with cut paper as a hydrophobic barrier, (c) a polymer-based device made with silicone rubber, and (d) a polymer-based device made with UV resin. The weight, thickness, and cost of each proposed device are listed.
SweatSkin device structure: (a) general design, (b) paper-based device, and (c) polymer-based device.
The workflow of SweatSkin: First, (a) the user determines the parameters of the device and the biomarkers they are interested in measuring. Second, (b) with the input from the previous step, the user can generate the basic design of the device and export an SVG file with the support software tool we developed. Third, (c) the SVG file can be imported into a 3D modeling tool to generate the molds for making polymer-based devices or a vector graphic editor to make some further designs. Last, (d) with the molds or the vector designs, polymer- or paper-based devices can be fabricated, respectively.
The workflow of fabricating paper-based devices using (a) wax and (b) cut paper as hydrophobic barriers. Step 1 (a1, b1): Create the channels. Step 2 (a2, b2): Position the test paper and channels. Step 3 (a3, b3): Punch the harvesting area. Step 4 (a4, b4): Seal the device. Step 5 (a5, b5): Apply the device onto the skin using the same method as applying a sticker.
The workflow of fabricating polymer-based devices using (a) silicone rubber and (b) UV resin. Step 1 (a1, b1): Cast the polymer in the mold. Step 2 (a2, b2): Scrap the exceeded polymer. Step 3 (a3, b3): Apply the hydrogel and test paper. Step 4 (a4, b4): Glue and seal the device. Step 5 (a5, b5): Apply the device onto the skin using the same method as applying a sticker.
We propose three applications designed and fabricated with the SweatSkin platform. The first one is a hydration state detection face painting for field day. The balloon will measure the pH value of sweat and change the color from orange (a1) to green (a2) when alkaline sweat is detected and indicates dehydration. The second one is a blood sugar monitor for diabetics. The sugar cubes above the coffee cup will change color from light blue (b1) to brown (b2) when glucose is detected in the sweat. The third one is a sweat loss measuring device for athletes (c1). The channels in the water bottle will gradually change color from blue (c2) to pink (c3). The area with color change indicates the amount of sweat loss.