Electrohydrodynamic Jet Printing of One‐Dimensional Photonic Crystals: Part I—An Empirical Model for Multi‐Material Multi‐Layer Fabrication

Electrohydrodynamic jet (e‐jet) printing is a high‐resolution additive manufacturing technique that holds promise for the fabrication of customized micro‐devices. In this companion paper set, e‐jet printing is investigated for its capability in depositing multilayer thin‐films with microscale spatial resolution and nanoscale thickness resolution to create arrays of 1D photonic crystals (1DPC). In this paper, an empirical model for the deposition process is developed, relating process and material parameters to the thickness and uniformity of the patterns. Standard macroscale measurements of solid surface energy and liquid surface tension are used in conjunction with microscale contact angle measurements to understand the length scale dependence of material properties and their impact on droplet merger into uniform microscale thin‐films. The model is validated with several photopolymer inks, a subset of which is used to create pixelated, multilayer arrays of 1DPCs with uniformity and resolution approaching standards in the optics manufacturing industry. It is found that the printed film topography at the microscale can be predicted based on the surface energetics at the microscale. Due to the flexibility in design provided by the e‐jet process, these findings can be generalized for fabricating additional multimaterial, multilayer micro‐ and nanostructures with applications beyond the field of optics.Herein, electrohydrodynamic jet (e‐jet) printing is investigated for its capability in depositing thin‐film, multi‐material, layered microstructures. An empirical model for the deposition process is developed, relating process and material parameters to film thickness. Standard macroscale measurements of surface energy and surface tension are used in conjunction with microscale contact angle measurements to understand material behaviors at the microscale.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163485/3/admt202000386_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163485/2/admt202000386.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163485/1/admt202000386-sup-0001-SuppMat.pd

Enhanced optical field intensity distribution in organic photovoltaic devices using external coatings

An external dielectric coating is shown to enhance energy conversion in an organic photovoltaic cell with metal anode and cathode by increasing the optical field intensity in the organic layers. Improved light incoupling in the device is modeled using transfer matrix simulations and is confirmed by in situ measurement of the photocurrent during growth of the coating. The optical field intensity in optimized cell geometries is predicted to exceed that in analogous devices using indium tin oxide, both cell types having equivalent anode sheet resistance, suggesting a broader range of compatible substrates (e.g., metal foils) and device processing techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87812/2/233502_1.pd

Thermoelectric and bulk mobility measurements in pentacene thin films

Low-noise thermoelectric and electrical measurements were used to derive the dependences of Seebeck coefficient and hole mobility on carrier concentration and grain size in the "bulk" regions of thermally evaporated pentacene thin films (in contrast to the channel field-effect mobility typically measured using thin-film transistor geometries). Distinct charge transport regimes were observed for larger (0.5 and 0.8 ??m) and smaller (0.2 ??m) grain sizes, attributed to carrier-dopant scattering and percolation, respectively.clos

Organic light-emitting device on a scanning probe cantilever

Organic light-emitting devices (OLEDs) were fabricated on scanning probe cantilevers using a combination of thermally evaporated molecular organic compounds and metallic electrodes. Ion beam milling was used to define the emissive region in the shape of a ring having a diameter of less than 5 μm5μm and a narrow width. Stable light emission was observed from the device at forward bias, with a current-voltage response similar to that of archetypal OLEDs. Based on this device, a novel electrically pumped scanning optical microscopy tool is suggested.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87792/2/111117_1.pd

Thermal and mechanical cracking in bis(triisopropylsilylethnyl)pentacene thin films

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/60466/1/21518_ftp.pd

Electrohydrodynamic Jet Printing of One‐Dimensional Photonic Crystals: Part I—An Empirical Model for Multi‐Material Multi‐Layer Fabrication

Electrohydrodynamic jet (e‐jet) printing is a high‐resolution additive manufacturing technique that holds promise for the fabrication of customized micro‐devices. In this companion paper set, e‐jet printing is investigated for its capability in depositing multilayer thin‐films with microscale spatial resolution and nanoscale thickness resolution to create arrays of 1D photonic crystals (1DPC). In this paper, an empirical model for the deposition process is developed, relating process and material parameters to the thickness and uniformity of the patterns. Standard macroscale measurements of solid surface energy and liquid surface tension are used in conjunction with microscale contact angle measurements to understand the length scale dependence of material properties and their impact on droplet merger into uniform microscale thin‐films. The model is validated with several photopolymer inks, a subset of which is used to create pixelated, multilayer arrays of 1DPCs with uniformity and resolution approaching standards in the optics manufacturing industry. It is found that the printed film topography at the microscale can be predicted based on the surface energetics at the microscale. Due to the flexibility in design provided by the e‐jet process, these findings can be generalized for fabricating additional multimaterial, multilayer micro‐ and nanostructures with applications beyond the field of optics.Herein, electrohydrodynamic jet (e‐jet) printing is investigated for its capability in depositing thin‐film, multi‐material, layered microstructures. An empirical model for the deposition process is developed, relating process and material parameters to film thickness. Standard macroscale measurements of surface energy and surface tension are used in conjunction with microscale contact angle measurements to understand material behaviors at the microscale.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163485/3/admt202000386_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163485/2/admt202000386.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163485/1/admt202000386-sup-0001-SuppMat.pd

Tunable substrate with electrodes for cardiomyocyte maturation compatible with high throughput testing

In vitro induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) can be used to test cardiotoxicity and study disease. When developing new drugs, cardiotoxicity needs to be tested. However, the immaturity of iPSC-CMs in vitro is a limitation. Studies have shown that physical and electrical stimulation aid in maturation of iPSC-CMs. Kirigami, the Japanese art of paper cutting, concepts are applied to design and create an easily manufacturable substrate. The krigami substrate in tandem with a custom well plate provide sufficient conditions for cardiomyocytes to mature while providing mechanical stimulation. Further, this design can be manufactured rapidly, allowing it to be compatible with high throughput testing.NAhttp://deepblue.lib.umich.edu/bitstream/2027.42/176713/1/weik_capstone_report__-_Katie_Wei.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/176713/2/weik_expo__poster_-_Katie_Wei.ppt

Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108628/1/aenm201400216.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/108628/2/aenm201400216-sup-0001-S1.pd