Inkjet Printable Metal Organic Framework Materials: UiO-66-(Hf) as A Ferroelectric Ink and Flexible Pressure Sensor
Research on Metal Organic Frameworks (MOFs) has escalated over the past years resulting in applications ranging from purification of water, air, and fuel to catalysis and sensing. MOFs have advantages that are quite unique; they are biocompatible, polymeric, light-weight and can have property-changing guest molecules. Inks using MOFs have been created in the past and used as chemical sensors among other applications. This research focuses on several major tasks starting with the synthesis of UiO-66-(Hf) with validated ferroelectric properties. This research further explored the conditions and processes to create functional inks suitable in inkjet deposition. Following post-processing/curing studies and sensor designs, demonstration is made using the developed UiO-66-(Hf) ink for its application in a flexible pressure sensor. This thesis documents details in synthesis of the UiO-66-(Hf) and successful inkjet printing using 5% (v/v) UiO-66-(Hf) in ethylene glycol. A waveform was created for the ink, which was optimized for the ceradrop f-series printer. Several drying methods were analyzed, including thermal treatment, UV and IR curing. The ferroelectric behavior of the UiO-66-(Hf) films was verified by piezo force microscopy (PFM) measurements, and the polarization-electric field (P-E) hysteresis loop was obtained. The pressure sensor was evaluated by being driven with a PZT and sensed the electric field on the frequency range 25 [kHz] to 100 [kHz]. The sensor was also measured with a vibrometer and it showed response for the frequency range 1562.5 [Hz] to 10 [MHz]. This range lies within the ultrasonic frequency range and somewhat within the acoustic, therefore applications as a flexible piezoelectric transducer as part of an ultrasonic device or a surface acoustic wave sensor (SAW) are possible. The measured D33 for MOF UiO-66-(Hf) was 35 [pC/N].