Liwei Lin (Advisor)

This paper presents a facile and low-cost fabrication method to construct microfluidic channels by means of a simple candle soot coating process. The fluid channels are defined via a shadow mask fabricated by a Kirigami cutting scheme and placed on top of a hydrophilic substrate. The candle-soot coating process is followed to convert the rest areas with the superhydrophobic property. High-resolution shadow masks can be built via the computer-aided design software. The resulting micro channels are found to have good inert chemical properties and remarkable durability for repeated usages....

To increase the energy utilization of a pMUT array, an advanced design scheme for asymmetrical piezoelectric micromachined ultrasonic transducers (pMUTs) has been developed with focused acoustic pressure via the deep deterministic policy gradient (DDPG) algorithm. Three distinctive accomplishments have been achieved in: 1) a highly-efficient interface platform between Python and COMSOL for asymmetry factor (AF) simulations; 2) fast freeform pMUT designs without the initial dataset; and 3) superior designs with increased 34% pressure outputs for potential applications such as contact-less...

This paper presents a mid-air haptic interface device enabled by a piezoelectric micromachined ultrasonic transducer (pMUT) array achieving an unprecedentedly high transmission pressure of 2900 Pa at a 15 mm distance for the first time. The structure is based on sputtered potassium sodium niobate (K,Na)NbO3 (KNN) thin film with a high piezoelectric coefficient (e31 ~ 8-10 C/m2). A prototype KNN pMUT array composed of 15×15 dual-electrode circular-shape diaphragms exhibits a resonant frequency around 92.4 kHz. Testing results show a transmitting sensitivity of 120.8 Pa/cm2 per volt under...

This work introduces contactless ultrasonic fluid viscosity and density monitoring using piezoelectric micromachined ultrasonic transducers (pMUTs) for the first time. Key advancements include: (1) non-contact and simultaneous liquid viscosity and density measurements; (2) 98% classification accuracy for four tested liquids; and (3) a mean absolute error (MAE) of 0.79 cp for a viscosity range from 0.98 cp to 39.44 cp, and a MAE of 12.6 kg·m⁻³ for a density range from 997.8 to 1035.3 kg·m⁻³. By removing the requirement for the direct contract of MEMS sensors to the testing fluid, this...