October 1, 2017.
Bioprinting is a manufacturing process that constructs devices from the bottom up by layering biomaterials in precise patterns. At Lawrence Livermore National Laboratory, bioprinting is performed using extrusion 3D printing, a process that uses pressure to drive the biomaterials through a syringe and on to a printing stage. These biomaterials are typically gel solutions with cells growing within. One drawback of these gels is that they are visco-elastic and non-Newtonian. This means that the mechanical properties of the gels change depending on the applied pressure. This variance in mechanical properties makes it harder to control the flow of these materials when the pressure applied changes leading to inconsistent dispensing. High precision dispensing is necessary to form the intricate microfluidic devices that are being developed at the lab. These materials also undergo a phase change during the printing process, further complicating the issue. To mitigate these issues, the lab aims to design a pressure feedback system that uses data from a flow sensor to control the pressure pumps to maintain desired flowrates. The lab was already in possession of calorimetric microfluidic flow meters used for other purposes; however, the accuracy of these sensors was unknown with visco-elatic materials. To verify the accuracy of these sensors, a test was developed to compare the flow sensor data with the actual flow rate. Gelatin solution was driven under constant pressure through the sensor and dispensed onto a mass balance. Using various conversions, data for volume accumulation and flowrate were obtained from both the mass balance and the flow sensor. The data from the flow sensor was compared to the data from the mass balance, which measured the true flowrate, to check for inconsistencies.
Lawrence Livermore National Laboratory (LLNL)
The 2017 STEM Teacher and Researcher Program and this project have been made possible through support from Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org), the California State University Office of the Chancellor, and California Polytechnic State University, in partnership with Lawrence Livermore National Laboratory.