fabrication of wearable multifunctional sensors on biodegradable, stretchable, and 3D complicated surfaces
Open Access
- Author:
- Yi, Ning
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 06, 2020
- Committee Members:
- Huanyu Cheng, Dissertation Advisor/Co-Advisor
Huanyu Cheng, Committee Chair/Co-Chair
Jian Yang, Committee Member
James Hansell Adair, Committee Member
Todd Palmer, Outside Member
John C Mauro, Program Head/Chair - Keywords:
- transient electronics
wearable electronics
gas sensor - Abstract:
- Skin-integrated, wearable electronics have attracted significant attention because of their unique role from preventative monitoring and diagnostic confirmation to convenient therapeutic options. The ultimate application of these bio-integrated devices for practical and convenient applications hinges on the seamless integration of on-body sensors. Multifunctional on-body sensors can precisely and continuously monitor the health conditions of the human body, whereas the wireless transmission modules can wirelessly power up the sensors and transmit the data generated from them to the cloud for the healthcare professionals. Conventional electronics are mainly fabricated on rigid and planar substrate, which is incompatible with the soft and complicated topography of human skin. To achieve successful application of electronics on human skins, this thesis demonstrates various strategies that can be used to build wearable multifunctional circuits. Biodegradable substrates from natural sources have gained broad interest due to the advantages of being biodegradable, recyclable, sustainable, and cost-efficient. More importantly, a strong adhesion between the biodegradable substrates and human skin can be achieved through a partial dissolution and softening of the substrates with the presence of water. As an alternative biodegradable material, galactomannan has direct relevance to the emerging biodegradable or transient electronics. Temperature sensor, electromyogram (EMG) sensor, and electrocardiogram (ECG) sensor have been fabricated on a thin biodegradable galactomannan film to fabricate a skin-attachable health monitoring device. Such a biodegradable multifunctional sensor pad is able to monitor body temperature, muscle activity, and heart beat rate in a real time manner. Soft and stretchable silicone elastomers such as polydimethylsiloxane (PDMS), Ecoflex, and Silbione, are also widely used as substrates for wearable electronics. Non-stretchable Electronic components can be integrated onto silicone elastomers substrate with properly designed structure or layout to achieve stretchability. The commonly used stretchable structures in wearable electronics include wrinkled structures from a pre-strain strategy, island-bridge layouts or serpentine interconnects, strain isolation layer, and their combinations. The stretchable multifunctional sensor pad is then able to accommodate the strain of human skin induced by body motions. Two types of stretchable gas sensor based on molybdenum disulfide@reduced graphene oxide (MoS2@rGO) and laser-induced graphene (LIG) are built for on-skin detection of NO2 as a demonstration. The good stretchability of the gas sensors enables accurate reading of the ambient NO2 level, even the sensors are stretched. Finally, the thesis presents a new fabrication method for constructing electronics on a 3D complicated surface. Deployment of functional circuits on a 3D freeform surface is of significant interest to wearable devices on curvilinear skin/tissue surfaces or smart Internet-of-Things with sensors on 3D objects. A new fabrication strategy that can directly print functional circuits either transient or long-lasting onto freeform surfaces by intense pulsed light-induced mass transfer of zinc nanoparticles (Zn NPs) is proposed. The intense pulsed light can locally raise the temperature of Zn NPs to induce evaporation. Laminating a soft semi-transparent polymer film with Zn NPs conforming to a 3D surface and expose the assembly to intense pulsed light can cause the evaporation and condensation of Zn on the 3D surface. A Zn based pattern can be obtained with the placement of shadow mask between the Zn NPs and the 3D surface. Immersing the Zn patterns into a copper sulfate or silver nitrate solution can further convert the transient device into a long-lasting device with copper or silver.