CAREER: Human motion driven capillaric circuits for skin-mountable biosensors

Musculoskeletal disorders, the leading cause of disability in the world, have been on the rise due to the aging human population and the main course of action in response to these conditions is improving the availability and efficacy of physical rehabilitation. Continuous monitoring of specific human movements using wearable devices would enable tracking of therapy progress, thus increase patient compliance and education in addition to enabling clinical studies investigating the relationship between rehabilitation exercises and health outcomes.

The goal of this CAREER project is to develop a skin patch incorporated with a capillaric circuit that functions as a micropump driven by human movement, which is an attractive approach for this purpose as it allows unique functionalities by combining fluid physics with wearables and human biomechanics. To inspire a broad range of students to study in STEM fields, the bioinspired device design and simple fabrication methods available in the PI’s lab will be used to produce educational kits for teaching human physiology and device physics to high school and college students, and teachers will be trained through a collaboration with the Santa Clara County Biotechnology Education Partnership program.

The investigator’s primary research goals are directed toward the development and application of implantable and miniaturized micro/optorfluidic technologies for biology and medicine. Toward this goal, this CAREER project aims to develop a bioinspired capillaric sensor patch for detecting skin strain-field (SSF) configurations correlated with a specific motion (e.g., facial or shoulder rehabilitation exercises etc.) Though skin-mounted microfluidic wearable devices for sweat and strain sensing have attracted significant attention, human movement has not been considered as the source of functionality in a microfluidic wearable device.

In this project, human skin biomechanics as a driving force for microfluidics will be investigated using digital image correlation (DIC) and the skin strain field (SSF) to measure a large range of movements. Capillaric sensor networks with electrical and image-based readouts will be designed for real-time wireless data transfer and fluidic data storage, respectively.

Ultimately, the interaction of the complex mechanical stimuli and the capillaric network components will be represented as a signal with elastomeric and dilatometric modes, which will significantly reduce the energy consumption and computational power required for complex movement analysis. For the time-dependent and multiplexed nature of the SSF, a computational method is needed for designing capillaric circuits for performing the desired analog and digital signal processing operations in the fluidic domain.

A microfluidic computer-aided design tool that models the capillaric circuit as an electrical circuit will be developed to find the device parameters. In addition to the device physics, this project will investigate the development of new manufacturing techniques for large-area skin-conformal microfluidic devices and stable electrode-ionic liquid interfaces.

These will serve towards the advancement of capillaric sensors for wearable technologies. An imperceptible skin-mountable patch that wirelessly transmits the number of repetitions of the physical rehabilitation exercises with the correct form and intensity to a master node (e.g., smart-watch or -phone) will be developed and these devices will be validated on volunteers in consultation with the Stanford Rehabilitation Center.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.