1. Thermal Inkjet Dispense for Pharmaceutical Research Lindsey Rucker, Hugh Hobbs, Ahson Saeed School of Chemical, Biological, and Environmental Engineering Is Mixing Achievable? HP applies their thermal inkjet printing technology to simplify the drug titration method. One HP consumable print head is loaded, which is capable of dispensing over a range of 15 pL to 1 µL. This leads to reduced labor costs and time requirements, and increased precision. Simplifies drug titration method Leads to reduced labor costs Reduction in time HP Direct Titration Method Improvements Over the Old Method Solution Traditional Method Drug discovery involves a titration process in which the effects of different concentrations of potential drug compounds are analyzed. Current methods of analysis involve steps which are labor intensive, error prone and, more importantly time consuming. Problem Challenge: Why Mixing Is Necessary DMSO penetrating in single point Cell death caused by high concentration at points of penetration. No Jitter Immediately after dispense 5 seconds after dispense 1 minute after dispense Cell death No Cell Death Immediately after dispense Jitter Jittering Method “Jittering”: oscillation of the well plate using the stage to induce shear between the deposited fluid, and fluid already in well. The stage can oscillate in the front to back direction (FB) or dual axis (FBLR). Quantitative Method A significant change in counts is caused by the solution not being fully mixed. Once the fluorescence signal, or counts, reaches a steady level, the conclusion can be made that mixing has occurred. This has been determined to be the best method to quantify mixing using kinetic data. VesselRadius Bond Number Theoretically Mix Standard water cup 45 mm 270Yes 96 well plate 3.5 mm 1.7Yes 384 well plate 1.9 mm 0.5No r= f luid density α = acceleration due to gravity L = radius of capillary tube g = surface tension of the interface Qualitative Method Bond Number: A ratio of the body forces to the surface tension forces. A bond number less than 1 indicates that the surface tension forces are dominating the body forces. In essence thermal inkjet technology consists of a resister and a fluid reservoir. The resister is positioned directly under (above) the filling reservoir. The resistor rapidly heats the fluid forming a bubble which pushes a drop of ink out of the nozzle. 16 of the nozzles depicted at the left are present on the printer heat used in the instrument. Two jittering methods were tested for mixing results: Jitter- while- dispense (JWD) and Jitter- post- dispense (JPD). JPD has been determined to be the optimal mixing method for both large and small dispense volumes, based on the slopes in the data plotted above. Plot A displays results for 50 nL dispense volume, and plot B displays results for 200 nL dispense volumes. Results Proposal The team recommends to use JPD in the FBLR direction for larger dispense volumes. JPD is also the optimal mixing method for small volumes, however, stage direction requires further testing. It is recommended to further investigate the jitter time and amplitude for both large and small dispense volumes. Thermal Inkjet and Titration Tool Thermal Inkjet TechnologyHewlett Packard Titration Tool and Print Head Acknowledgements The Engineering Team would like to thank: Hewlett Packard Kenneth Ward Heather Paris Ken Duda Michael J Day Philip H Harding HP Method Traditional Method A B