Screen-printable polymer fabrication with applications to wearable nanocomposite electronics and microfluidic systems

Wearable devices and systems are already important to our lives and have the potential for even greater impact. Many researchers are developing wearable devices and systems, and many different technologies are investigated. However, most of these technologies have limitations in flexibility, long fabrication times, lack of reusability, or complicated attachment mechanisms. Furthermore, many systems are limited in the functions that they can perform. Most systems are also confined to electronic functionality; there is not a fully successful wearable microfluidic technology developed with wearable fluidic channels for microfluidic devices, e.g., foldable microfluidic mixers or flexible bio-fluid sensors for wearable analysis systems. As an alternative approach, we develop new methods to screen-print electronic and fluidic devices on clothing that employ materials designed specifically for printing on textile. We present a new screen-printable silver conductive nanoparticle composite polymer (C-NCP) that can be applied to wearable systems for electronic functionality. We also develop a new technique to realize fully wearable microfluidic devices. Screen printable C-NCPs benefit the development of wearable devices due to their high degree of flexibility, good conductivity, and ability to be easily patterned into electrical and microfluidic devices. The new microfluidic device fabrication method enables easy, simple, and fast development of wearable microfluidic devices using inexpensive materials and equipment. In this thesis, a screen-printable C-NCP is developed and characterized, and its potential for wearable devices and systems is explored through a variety of demonstrator systems. The new microfluidic device fabrication method is explained in detail with optimization and characterization. Passive wearable microfluidic devices are fabricated on fabric, and active wearable microfluidic devices with electrical structures are also fabricated by combining wearable microfluidic structures with silver C-NCP as electronic routing and electrodes. The following demonstration devices and systems are developed to showcase different aspects of the new materials and fabrication techniques: 1) flexible dry electrocardiogram (ECG) electrodes screen printed on textile to measure heart bioelectrical signals; 2) flexible electrical routing printed on a safety vests for LED attachment and lighting system demonstration; 3) wearable microfluidic mixer fabricated on textiles; 4) and a wearable fluid conductivity sensor that combines C-NCP with flexible microfluidics.