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Direct Printing/Patterning of Key Components for Biosensor Devices

Recently, biosensor devices, especially wearable devices for monitoring human health, have attracted significant interests and meanwhile, they have a huge market. These wearable biosensor devices usually consist of several key components, including microfluidics, biosensing elements and power supply. Though advanced sensing platforms have been extensively explored, high manufacturing fee and lack of practical functions are the main reasons that most of devices and techniques are still out of reach for potential users. This dissertation focuses on fabricating these key components for biosensor devices via advanced printing/patterning techniques, such as inkjet-printing and nanoimprinting. These fabrication techniques can be potentially extended to roll-to-roll manufacturing system, allowing for low fabrication costs. Using UV-assisted nanoimprint lithography, flexible microfluidic devices were fabricated with thiol-ene click photopolymer on polymeric substrate. As for sensing elements, inkjet-printed electrodes were applied for electrochemical detections of multiple analytes. Here, inkjet-printed Au electrodes were applied for measuring salmonella concentration with magnetic beads. Glucose and cortisol sensing were developed with inkjet-printed graphene electrodes. These two sensors were compatible with “smart band-aid” platform for wearable monitoring. With synthetic skin, the real-time monitoring of glucose concentration was achieved, and the effect of flow rate was examined in detail. Inkjet-printed electrodes can be easily customized for various applications, though their resolutions are mostly limited to ~20 microns. It is hard to develop materials within nanoscale resolution via inkjet-printing. To develop nanostructured materials, nanoimprint lithography is introduced as a direct patterning method. Several kinds of metal oxide multilayer woodpile nanostructured electrodes were developed. The aspect ratio of the final structure can be easily customized by the number of layers. Furthermore, we examined the performance of these woodpile electrodes in electrochemical applications. For example, CeO2 woodpile electrodes were used for enzymatic glucose sensors, while TiO2 woodpile electrodes were applied as lithium-ion electrodes. The structure-processing combination can lead to efficient use of these electroactive materials. Finally, we utilized solvent-assisted nanoimprint lithography to process cellulose nanomaterials into nanostructure. Cellulose, as a major component of plant, is the most abundant biomaterial in nature. The development of patterned cellulose films can be potentially used as novel, green substrates in many applications, including wearable biosensing devices.
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