Category: Automation and High-Throughput Technologies
Measurements of an object’s fundamental physical properties like mass, volume, and density can offer valuable insights into an object’s composition or state. For objects in air, conventional laboratory balances can easily be used to measure the object’s mass, volume, and density. But for small objects in fluid (like microorganisms, biodegradable medical implants, or drug-releasing particles), the fluid environment of these objects is incompatible with conventional measurement techniques. In this work, we show a novel method for continuously monitoring the mass, volume, and density of any microgram-sized object in fluid. We accomplish this using glass tubes bent into diving-board or tuning-fork shapes. The tubes are vibrated at their resonance frequency; this frequency is a function of the mass of the fluid contents of the tubes. When a particle flows through the tube, the resonance frequency of the tube briefly changes by an amount proportional to the buoyant mass of the particle. In this manner, we can continuously and automatically measure the mass of any particle in fluid every few seconds, with microgram accuracy, for a virtually limitless amount of time. And by measuring a particle in fluids of different densities, we can also determine the volume and density of the particle. Because all objects have properties like mass and density, our technique is applicable to a wide variety of different fields. We highlight the versatility of our sensor by using it in a variety of different proof-of-concept applications, including measuring the extremely slow degradation rates of a biodegradable magnesium material for medical implants, measuring the degradation rates of single particles of a controlled-release pharmaceutical, and measuring plant tissue samples in hopes of identifying healthy and diseased citrus plants. Our sensor’s ability to make particle mass, volume, and density measurements continuously, in any fluidic environment, and with high sensitivity should make the sensor a powerful tool in many different fields.
Heran Bhakta– Graduate Student Researcher, University of California, Riverside, Riverside, CA