UC Riverside

Accurate measurements of an object’s fundamental physical properties like mass, volume, and density can provide valuable insights about an object and how it behaves. This is especially true for biological or bioengineered samples that reside in liquid environments. In this thesis, we demonstrate a new method for quantifying the mass, volume, and density of samples in their native liquid environments using resonating mass sensors. By vibrating a liquid-filled glass tube at its resonance frequency and passing a solid sample through the tube, the tube’s resonance frequency changes by an amount that is inversely proportional to the sample’s buoyant mass. This enables microgram-scaled objects to be measured in their native liquid environment with nanogram resolution, without the need for labels or tags. Sensor applications are demonstrated by studying the degradation rates of biomaterials, measuring the physical properties of hydrogels, and evaluating the dissolution rates of drug delivery systems.

In addition to vibrating glass tubes, a low-cost method for measuring liquid density is presented utilizing a 3000-year-old musical instrument called the Mbira. By modifying the metal tine of the Mbira, a density resolution of 0.012 g/mL is achieved, making it an accessible tool for resource-limited settings. This low-cost method has the potential to be a powerful tool for determining the authenticity of liquid medications in developing countries. This idea is expanded by exploring alternative designs for low-cost density meter designs for chemical analysis. We present a simple 3D-printed sensor capable of measuring the density of a substance with high precision. The plastic tuning forks are shown to offer several advantages over their metal counterparts, including reduced costs, increased durability, and improved design flexibility. By providing an inexpensive and easy-to-use method for testing the purity or chemical identity of a sample, these plastic resonators can find uses in many applications, particularly in low-resource settings and developing regions at a low cost.