Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 119419

119419 - Characterization of Biofouling on Thermal Bubble-Driven Micro-Pumps 

Thermal bubble-driven micro-pumps are an upcoming micro-pump technology designed to move fluid without the use of external pumps. These micro-pumps can be directly integrated into micro/milli-fluidic channels leveraging existing semiconductor mass fabrication techniques making this technology promising to enable true lab-on-a-chip technologies. Physically, thermal bubble-driven micro-pumps are thin film, high-power resistors that utilize microsecond heating pulses to rapidly boil fluid on the resistor's surface, which creates a high-pressure vapor bubble to perform mechanical work. These micro-pumps are a highly versatile technology platform, and recent efforts have demonstrated the ability to realize a variety of fluidic operations such as pumping, mixing, sorting, routing, and even cell lysis. However, to date, research on thermal bubble-driven micro-pumps have focused on fundamental fluid operations, and little work has investigated how this technology platform interacts and operates with biofluids such as blood or protein-rich fluids. In this work, we characterize how biofluids interact with thermal bubble-driven micro-pumps in order to build a foundation for the use of these micro-pumps for biological applications.

 

In this study, diluted defibrinated bovine blood (20% blood by weight in PBS solution) and albumen dissolved in PBS solution (4.5g/100mL)  were placed over a thermal bubble-driven micro-pump with no channel confinement. High-power resistors, which make up the thermal bubble-driven micro-pump, were fabricated utilizing a femtosecond laser cutter to cut micro-resistors (dimensions of 300 x 700 um) on an ITO-coated sheet of glass. A custom electrical setup was used to deliver a 5 us heating pulse at 100-150 V (total power of 300-400 W), causing explosive boiling at the resistor’s surface. The vapor bubble dynamics were imaged using a custom stroboscopic imaging setup capable of recording at 1-20 Mfps. Biofouling from both defibrinated bovine blood and albumen PBS solution was found to significantly degrade the micro-pump efficacy and create a fouling layer on the resistor surface. Over time, the protein buildup on the resistor’s surface degraded the maximum bubble area until the resistor fully failed. A scanning electron microscope (SEM) was used to characterize the protein buildup on the resistor’s surface. We show that biofouling on the surface of the resistor increases with the number of firing events and causes the vapor bubble to decrease in size as the fouling layer causes decreased heat transfer from the resistor’s surface to the fluid, which creates thermal stresses on the resistor leading to failure. Specifically, it was found that complete failure occurred after approximately 5000 firing events with the albumen PBS solution, which is far below what is needed for commercial application of this technology (> 10^7 firing events). Future work will investigate the use of barrier layers to mitigate biofouling on the surface of these micro-pumps. Ultimately, thermal bubble-driven micro-pumps are a promising solution to enable lab-on-a-chip technologies but research is needed on their interaction with biofluids. This work identifies that biofouling is a significant challenge when using these micro-pumps with biological fluids, and additional work with barrier layers to prevent resistor degradation and failure will be needed before the successful commercialization of this technology for biological applications. 

Presenting Author: Daimean Solis University Of Colorado Boulder

Presenting Author Biography: Daimean is an undergraduate student at the University of Colorado Boulder studying biomedical engineering. He is an undergraduate researcher with a focus on thermal bubble-driven micro-pumps and their interaction with biofluids. His current interests are in biomedical engineering and improving medical device accessibility.

Authors:

Daimean Solis University Of Colorado Boulder
Brandon Hayes University Of Colorado Boulder
Robert Maccurdy University Of Colorado Boulder