Browsing by Subject "Inkjet printing"
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Item Dissolving and coated microneedles as useful drug delivery platforms(2022-04-27) Tarbox, Tamara Nina; Williams, Robert O., III, 1956-; Smyth, Hugh D. C.Microneedles are a useful dosage form that combine key advantages of drug delivery by injection with advantages of transdermal drug delivery, while also overcoming some of the most notable limitations of these two therapeutic delivery modalities. Despite the potential utility of microneedles as a therapeutic dosage form, numerous challenges remain in satisfying the regulatory burden required to achieve FDA marketing approval. In Chapter 1, recent improvements in potentially scalable coating and manufacturing procedures for microneedles were reviewed. Advantages and limitations of certain types of microneedles, along with specific examples of manufacturing techniques were discussed, along with further improvements and regulatory considerations. In Chapter 2, an update on clinical development over the last five years including solid, coated, and dissolving microneedles was presented. Progress and results for selected clinical studies were discussed in detail.Item Evolutionary controllers for identifying viable regimes and obtaining optimal performance in precision inkjet systems(2019-12-06) Snyder, Brent Andrew; Sreenivasan, S.V.; Djurdjanovic, Dragan; Longoria, Raul G; LaBrake, DwayneDrop on demand piezoelectric inkjets have become an important device for direct patterning and adaptive material deposition in micro- and nano-fabrication applications. Key performance, reliability, and cost metrics for piezo-jets include drop volume minimization, drop volume accuracy and precision, drop placement accuracy, drop velocity, hours of continuous operation, and throughput. Accurately predicting drop formation from an actuation waveform using physics-based models is challenging as such models require knowledge of several inkjet parameters that cannot be determined non-destructively. Current practice involves ad-hoc manual recalibration of the actuation waveform to obtain reliable jetting of a variety of materials. This prevents the use of higher order waveforms defined by large numbers of parameters, where such waveforms have been demonstrated in the literature to achieve more aggressive performance metrics than lower order waveforms. This dissertation presents automatic piezo-jet waveform tuning methods based on evolutionary algorithms and computer-vision-based monitoring drops in-flight and drops that have been dispensed onto a substrate. Actuating and monitoring a piezo-jet as part of a “machine-in-the-loop” optimization scheme circumvents the need for complex forward models, as key performance metrics are estimated from images of actual jetted drops. Automatic tuning also enables exploration of previously unachievable highly complicated higher order waveforms comprised of more than a hundred parameters. In this dissertation, three fixed waveform topologies of increasing complexity were applied to optimize waveforms using genetic algorithms (GA) for a single-nozzle inkjet based on computer vision feedback from in-flight drop monitoring. These GA experiments automatically found waveforms for water and ethyl acetate, wherein the latter is considered rheologically impossible to jet based on fluid mechanics studies in the literature, but which was jetted at drop volumes measuring 0.8 pL continuously for several hours without faults. The resulting ratio between the 11.5 µm drop diameter and the 50 µm inkjet nozzle aperture was an impressive 23%. Next, a novel optimization scheme of a GA with a variable-length or “free” topology was developed to optimize waveforms for a more complex multi-nozzle piezo-jet using top-down imaging of drops dispensed on a silicon wafer to measure performance. This free-topology GA enabled exploration of highly sophisticated controllers and resulted in waveforms with as many as 124 parameters that reduced drop volume by 22.8% to an estimated 336 fL as compared to the waveforms found by a fixed-topology GA with 13 parameters.Item Inkjet printed single-walled carbon nanotube field effect transistors(2016-05) Jang, Seonpil; Dodabalapur, Ananth, 1963-; Akinwande, Deji; Chen, Ray; Ho, Paul; Yu, GuihuaInkjet printing technology has the potential to drastically reduce the process time and cost by generating the patterns without physical masks and conventional vacuum processes. In addition, the inkjet printing process can be applied to flexible and large area substrates. Among the printable semiconductors, single walled carbon nanotubes (SWCNTs) have been attracting increasing attention for their high carrier mobility and potential application in transparent, flexible, high- current and high frequency electronics. The effects of fluoropolymer capping onto SWCNT devices are investigated. Remarkable improvements in key device characteristics of SWCNT field-effect transistors (FETs) are achieved by coating of the active semiconductor with a fluoropolymer layer such as poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). These favorable changes in device characteristics also enhance circuit performance. The origins of these improvements are the dipolar nature of the fluoropolymer and the mechanism is confirm by exposing SWCNT FETs to a number of vapor phase polar molecules which produce similar effects on the FET characteristics as the application of P(VDF-TrFE). High-performance inkjet printed single walled carbon nanotube (SWCNT) field effect transistors (FETs) with channel lengths of 150-250 nm are demonstrated. Optimized electrode geometry has been developed to confine the inkjet droplet to the active channel area. This minimizes waste of material outside of the channel while enabling short channel length devices that exhibit high effective carrier mobilities and transconductances. This novel fabrication approach is compatible with roll-to-roll processing and enables the formation of high-performance short channel device arrays based on inkjet printing with at least a 50-fold reduction in consumption of semiconducting SWCNT ink compared to other solution processing methods. In these short channel SWCNT FETs, the influences of nanotube bending and gate insulator-semiconductor interface modification on the characteristics of inkjet printed short channel length SWCNT are investigated. Employing recessed source and drain (S/D) electrodes to minimize the mechanical distortion of CNTs, high performance short channel ambipolar transistors based on inkjet printed SWCNTs are demonstrated. Mechanical distortion of the nanotubes due to bending near source and drain contacts when they are not recessed is found to suppress electron transport and transform the ambipolar transistors into p-type devices. Inclusion of interfacial polymer layers such as P(VDF-TrFE) between the SWCNTs and Al2O3 top dielectric also results in p-type doping and reductions in electron transport transforming amibipolar transistors into p-type devices.