Mechanics-Driven Nano-Manufacturing Technologies in Liquid Environments

Micro/nanoscale electronic devices and systems have attracted ever-growing attention in healthcare applications over the past decades due to low-cost and high accessibility yet easy-customizable functions with only the demand of a small sample volume in high measurement accuracy. The continuous development, in particular, supported by the emerging of new materials, capable of meeting critical needs in next-generation, sustainable, wearable, and multifunctional biomedical devices for at-home, personalized healthcare monitoring and disease diagnose is challenging the principles and strategies of structural design and manufacturing and their seamless integration toward the realization of precision healthcare. The dissertation outlines three main objectives: (1) designing biomedical devices in response to different stimuli and sensing environments, (2) exploring manufacturing principles with an emphasis on soft materials to match the mechanical properties of human organs, and (3) proposing applications that seamlessly integrate structural design and manufacturing in the biomedical field.

Chapter 1 provides an introduction to the challenges faced by micro/nano-electronic devices in biomedicine and explores the potential of liquid-assisted manufacturing. The chapter presents the research objectives and methods. Chapter 2 introduces a 3D-printed microheater integrated with a drug-encapsulated microneedle patch system for drug delivery. The chapter details the formulation of an ink solution using polydimethylsiloxane (PDMS) and multiwalled carbon nanotubes (MWCNTs) to create crack-free, stretchable microheaters. The integration performance of the microheaters on the microneedle patch is evaluated, and drug release into the skin is confirmed. This technology enables the development of sensor-controlled smart microneedle patch systems integrated with wearable electronics for biomedical research. Chapter 3 presents an electrical sensing-based, reusable, cellular microfluidic device for fast urinalysis. Soft porous scaffolds decorated with conductive multiwalled carbon nanotubes enable physical interaction with biomarkers in urine. The device demonstrates sensing capability, sensitivity, and reusability for monitoring biomarkers by programming mechanical deformation of the porous scaffolds. Ex vivo experiments confirm the device's diagnostic robustness in disease mouse models, offering a low-cost bioelectronic device for rapid disease diagnosis. Chapter 4 introduces a novel liquid-based inkjet printing method that replaces solid substrates with amorphous liquid substrates. The chapter establishes a theoretical model to determine the spreading ratio of ink droplets on a two-layer liquid substrate and validates it through experiments. The printed patterns exhibit superior quality compared to traditional solid-based printing techniques, with selective applications for the developed method. Chapter 5 demonstrates the fabrication of a battery-free chipless RFID tag sensor using the liquid-based inkjet printing method. The sensor features uniform thickness and stretchability. The RFID communication properties are characterized, and successful data readout is achieved under various environmental conditions. The sensor's practical application is validated through real-time monitoring of milk and banana spoilage, showcasing its accurate data recording capabilities and potential widespread implementation. Chapter 6 summarizes the major findings and discusses future research directions. The research contributes to the advancement of mechanics-centered designs and manufacturing strategies for biomedical engineering and healthcare monitoring, enabling the development of portable, accessible, and highly reliable biomedical devices for diverse applications.