Reinhold Dauskardt - Academia.edu (original) (raw)

Papers by Reinhold Dauskardt

ACS applied materials & interfaces, Jan 19, 2015

We demonstrate a dual organic and inorganic precursor method to deposit transparent organosilicat... more We demonstrate a dual organic and inorganic precursor method to deposit transparent organosilicate protective bilayer coatings on poly methyl methacrylate (PMMA) substrates with atmospheric plasma deposition in ambient air. The bottom layer was a hybrid organosilicate adhesive layer deposited with dual organic 1,5-cyclooctadiene (CYC) and widely used inorganic tetraethoxysiline (TEOS) precursors. The selection of the organic CYC precursor allowed incorporation of a carbon chain in the organosilicate adhesive layer, which resulted in improved adhesion. The top layer was a dense silica coating with high Young's modulus and hardness deposited with TEOS. The deposited bilayer structure showed ∼100% transparency in the visible light wavelength region, twice the adhesion energy, and five times the Young's modulus of commercial polysiloxane sol-gel coatings.

2009 IEEE International Conference on 3D System Integration, 2009

Low-temperature aluminum-germanium (Al-Ge) eutectic bonding has been investigated for monolithic ... more Low-temperature aluminum-germanium (Al-Ge) eutectic bonding has been investigated for monolithic three-dimensional integrated circuits (3DIC) applications. Successful bonds using Al-Ge bilayer films as thin as 157 nm were achieved at temperatures as low as 435degC, when applying 200 kPa down-pressure for 30 minutes. The liquid phase of the eutectic composition ensured a seamless and void-free bond. The fracture energy of the Al-Ge bond (630 nm thick) was measured to be Gc = 50.5 plusmn 12.7 J/m2, using double cantilever beam thin-film adhesion measurement technique. An array of silicon islands was attached onto an amorphous SiO2 wafer using low-temperature Al-Ge bonding. These islands could be used to form devices on upper layers of monolithically integrated 3DICs.

Macromolecules, 2014

ABSTRACT For semiconducting polymers, such as regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3... more ABSTRACT For semiconducting polymers, such as regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT), the molecular weight has been correlated to charge carrier field-effect mobilities, surface morphology, and gelation rates in solution and therefore has important implications for long-term reliability, manufacturing, and future applications of electronic organic thin films. In this work, we show that the molecular weight rr-P3HT in organic solar cells can also significantly change the internal cohesion of the photoactive layer using micromechanical testing techniques. Cohesive values ranged from 0.5 to 17 J m–2, following the general trend of greater cohesion with increasing molecular weight. Using nanodynamic mechanical analysis, we attribute the increase in cohesion to increased plasticity which helps dissipate the applied energy. Finally, we correlate photovoltaic efficiency with cohesion to assess the device physics pertinent to optimizing device reliability. This research elucidates the fundamental parameters which affect both the mechanical stability and efficiency of polymer solar cells.

Advanced Materials, Mar 1, 2020

Bacterial infections remain a leading threat to global health because of the misuse of antibiotic... more Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat generated around the target sites often damage host cells and lengthen the healing time. Here, we report a localized thermal managing strategy, a thermaldisrupting interface induced mitigation (TRIM), to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimize the risk of skin damage and function loss during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface feature plays a critical role in maintaining intercellular cohesion of epidermis during photothermal therapy. Finally, endowing wound dressing with TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effect of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy.

The research on the fracture and fatigue crack-growth behavior of single crystal intermetallics w... more The research on the fracture and fatigue crack-growth behavior of single crystal intermetallics was motivated by the need for improved high temperature engineering materials. The approach using a first principles total energy calculation of the energies of {001} and {110} surfaces in NiAl, by Yoo and Fu predicts very low fracture toughness vs. experimental findings. As the program has developed, the focus has shifted to the use of thermal barrier and wears resistant coatings to improve material behavior at high temperature and other extreme service conditions. The present emphasis therefore to develop thermal barrier and wear resistant coating systems with improved integrity and long term reliability. The major accomplishment of this work has been the development of fracture-mechanics based techniques to accurately and reproducibly measure the fracture resistance (or adhesion) of coating systems. We believe the data presented to be unique for the two coating systems characterized. Interface toughness, K , data was obtained for several specimens containing multi-layer systems of PSZ-NiAl-Pt-Superalloy and TiAlN-Cermet. The interfaces prone to fracture were identified. Experiments were also completed to analyze crack-growth under cyclic fatigue loading of these interfaces.

Nature Communications, Oct 18, 2017

Hyperconnected network architectures can endow nanomaterials with remarkable mechanical propertie... more Hyperconnected network architectures can endow nanomaterials with remarkable mechanical properties that are fundamentally controlled by designing connectivity into the intrinsic molecular structure. For hybrid organic-inorganic nanomaterials, here we show that by using 1,3,5 silyl benzene precursors, the connectivity of a silicon atom within the network extends beyond its chemical coordination number, resulting in a hyperconnected network with exceptional elastic stiffness, higher than that of fully dense silica. The exceptional intrinsic stiffness of these hyperconnected glass networks is demonstrated with molecular dynamics models and these model predictions are calibrated through the synthesis and characterization of an intrinsically porous hybrid glass processed from 1,3,5(triethoxysilyl) benzene. The proposed molecular design strategy applies to any materials system wherein the mechanical properties are controlled by the underlying network connectivity.

$Research paper thumbnail of Crack tip shielding in fracture and fatigue: extrinsic versus intrinsic toughening$

Work undertaken a t : M a te r ia ls and Chemical Sciences D iv is io n , Lawrence B e rk e le y ... more Work undertaken a t : M a te r ia ls and Chemical Sciences D iv is io n , Lawrence B e rk e le y L a b o ra to ry , Department o f M a te r ia ls Science and M in era l E n g in e erin g , U n iv e rs ity o f C a li f o r n ia , B e rk e le y , CA 94720. A th e s is subm itted to th e F a c u lty o f E n g in e e rin g , U n iv e rs ity o f the W itw aters ran d , Johannesburg, in f u lf i l l m e n t o f th e requ irem en ts fo r th e Degree o f Doctor o f Philo so p h y.

Nature Communications, Jul 3, 2020

Intrinsically and fully stretchable active-matrix-driven displays are an important element to ski... more Intrinsically and fully stretchable active-matrix-driven displays are an important element to skin electronics that can be applied to many emerging fields, such as wearable electronics, consumer electronics and biomedical devices. Here, we show for the first time a fully stretchable active-matrix-driven organic light-emitting electrochemical cell array. Briefly, it is comprised of a stretchable light-emitting electrochemical cell array driven by a solutionprocessed, vertically integrated stretchable organic thin-film transistor active-matrix, which is enabled by the development of chemically-orthogonal and intrinsically stretchable dielectric materials. Our resulting active-matrix-driven organic light-emitting electrochemical cell array can be readily bent, twisted and stretched without affecting its device performance. When mounted on skin, the array can tolerate to repeated cycles at 30% strain. This work demonstrates the feasibility of skin-applicable displays and lays the foundation for further materials development.

The three-dimensional configurational arrangement of natural and synthetic network materials dete... more The three-dimensional configurational arrangement of natural and synthetic network materials determines their application range. Control of the real time incorporation of each building block, hence, all functional groups is desired so that we can regulate macroscopic properties from the molecular level onwards. Here we interconnect kinetic Monte Carlo simulations from the field of chemical kinetics and molecular dynamic simulations from the field of physics. We visualize for (in)organic network material synthesis how the initial building blocks interact timewise and spatially, accounting for variations in inter- and intramolecular chemical reactivity, diffusivity, segmental compositions, branch/network point locations, and defects. We use the kinetic and three-dimensional structural information to construct structure-property relationships based on molecular descriptors such as the molecular pore size or dangling chain distribution, differentiating between ideal and non-ideal struct...

SSRN Electronic Journal, 2021

Perovskite photovoltaics (PV) have achieved rapid development in the past decade in terms of powe... more Perovskite photovoltaics (PV) have achieved rapid development in the past decade in terms of power conversion efficiency of small-area lab-scale devices; however, successful commercialization still requires further development of low-cost, scalable, and high-throughput manufacturing techniques. One of the key challenges to the development of a new fabrication technique is the high-dimensional parameter space, and machine learning (ML) can be used to accelerate perovskite PV scaling. Here, we present an ML-guided framework of sequential learning for manufacturing process optimization. We apply our methodology to the Rapid Spray Plasma Processing (RSPP) technique for perovskite thin films in ambient conditions. With a limited experimental budget of screening 100 conditions process conditions, we demonstrated an efficiency improvement to 18.5% for the best device, and we also experimentally found 10 unique conditions to produce the top-performing devices of more than 17% efficiency, which is 5 times higher rate of success than pseudo-random Latin hypercube sampling. Our model is enabled by three innovations: (a) flexible knowledge transfer between experimental processes by incorporating data from prior experimental data as a soft constraint; (b) incorporation of both subjective human observations and ML insights when selecting next experiments; (c) adaptive strategy of locating the region of interest using Bayesian optimization first, and then conducting local exploration for high-efficiency devices. Furthermore, in virtual benchmarking, our framework achieves faster improvements with limited experimental budgets than traditional design-of-experiments methods (e.g., one-variable-at-a-time sampling). This framework is shown to enable researchers' domain knowledge in the ML-guided optimization loop; therefore, it has the potential to facilitate the wider adoption of ML in scaling to perovskite PV manufacturing.

Minerals, 2020

In this work, the effect of layer charge density of Na-montmorillonite (Na-MT) and carbon chain l... more In this work, the effect of layer charge density of Na-montmorillonite (Na-MT) and carbon chain length of alkyl ammonium on the structure and gel property of organo-montmorillonite (organo-MT) was studied by using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric (TG) analysis, contact angle test, molecular dynamics (MD) simulation, and gel apparent viscosity determination experiment. The results of XRD show that Na-MT with lower layer charge density is easier to swell after intercalation of alkyl ammonium, and the basal spacing of organo-MT increases with the increase of carbon chain length. The results of FTIR show that the absorption bands at 2924 cm−1 and 2853 cm−1 shift towards low frequency region with the increase of carbon chain length, and the absorption bands at 515 cm−1 and 463 cm−1 move towards high frequency region when the layer charge density increases. The mass loss of organo-MT evidently increases with the increase of layer charge density...

ACS Applied Materials & Interfaces, 2018

Sputter processed oxide films are typically annealed at high temperature (activation process) to ... more Sputter processed oxide films are typically annealed at high temperature (activation process) to achieve stable electrical characteristics through the formation of strong metaloxide chemical bonds. For instance, indium-gallium-zinc oxide (IGZO) films typically need a thermal treatment at 300°C for ≥1 hour as an activation process. We propose an open-air plasma treatment (OPT) to rapidly and effectively activate sputter processed IGZO films. OPT effectively induces metal-oxide chemical bonds in IGZO films at temperatures as low as 240 o C with a dwell time on the order of a second. Furthermore, by controlling the plasma processing conditions (scan speed, distance a between plasma nozzle and samples, and gas flow rate), the electrical characteristics and the microstructure of the IGZO films can be easily tuned. Finally, OPT can be utilized to implement a selective activation process. Plasmatreated IGZO thin film transistors (TFTs) exhibit comparable electrical characteristics to those of conventionally thermal treated IGZO TFTs. Through in-depth optical, chemical, and physical characterizations, we confirm that OPT simultaneously dissociates weak chemical bonds by UV radiation and ion bombardment, and reestablishes the metal-oxide network by radical reaction and OPT-induced heat.

Nano letters, Aug 11, 2018

Ultrathin nanowires with <3 nm diameter have long been sought for novel properties that emerge... more Ultrathin nanowires with <3 nm diameter have long been sought for novel properties that emerge from dimensional constraint as well as for continued size reduction and performance improvement of nanoelectronic devices. Here, we report on a facile and large-scale synthesis of a new class of electrically conductive ultrathin core-shell nanowires using benzenethiols. Core-shell nanowires are atomically precise and have inorganic five-atom copper-sulfur cross-sectional cores encapsulated by organic shells encompassing aromatic substituents with ring planes oriented parallel. The exact nanowire atomic structures were revealed via a two-pronged approach combining computational methods coupled with experimental synthesis and advanced characterizations. Core-shell nanowires were determined to be indirect bandgap materials with a predicted room-temperature resistivity of ∼120 Ω·m. Nanowire morphology was found to be tunable by changing the interwire interactions imparted by the functional ...

ACS applied materials & interfaces, Jan 25, 2018

Phenyl-C-butyric acid methyl ester (PCBM) is universally used as the electron-transport layer (ET... more Phenyl-C-butyric acid methyl ester (PCBM) is universally used as the electron-transport layer (ETL) in the low-cost inverted planar structure of perovskite solar cells (PeSCs). PCBM brings tremendous challenges in upscaling of PeSCs using industry-relevant methods due to its aggregation behavior, which undermines the power conversion efficiency and stability. Herein, we highlight these, seldom reported, challenges with PCBM. Furthermore, we investigate the potential of nonfullerene indacenodithiophene (IDT)-based molecules by employing a commercially available variant, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3- d:2',3'- d']- s-indaceno[1,2- b:5,6- b'] dithiophene (ITIC), as a PCBM replacement in ambient-processed PeSCs. Films fabrication by laboratory-based spin-coating and industry-relevant slot-die coating methods are compared. Although similar power-conversion efficiencies are achieved with both types o...

Chemistry of Materials, 2017

ACS applied materials & interfaces, Jan 20, 2016

Carbon-bridges were successfully incorporated into the molecular structure of inorganic silicate ... more Carbon-bridges were successfully incorporated into the molecular structure of inorganic silicate films deposited onto polymer substrates using an oxidative atmospheric plasma deposition process. Key process parameters that include the precursor chemistry and delivery rate are discussed in the context of a deposition model. The resulting coating exhibited significantly improved adhesion and a 4-fold increase in moisture resistance as determined from the threshold for debonding in humid air compared to dense silica or commercial sol-gel polysiloxane coatings. Other important parameters for obtaining highly adhesive coating deposition on oxidation-sensitive polymer substrates using atmospheric plasma were also investigated to fully activate but not overoxidize the substrate. The resulting carbon molecular bridged adhesive coating showed enhanced moisture resistance, important for functional membrane applications.

Nanoporous organosilicate thin-film glasses are superior candidates for use as ultra-low-k interl... more Nanoporous organosilicate thin-film glasses are superior candidates for use as ultra-low-k interlayer dielectrics in advanced microelectronic devices. However, it has been recently reported that aqueous solutions containing organic species can readily diffuse in the film, despite the hydrophobic nature of the film, and increase the k value during processing [1,2]. Of particular concern is the chemical mechanical planarization (CMP) process in which these extremely brittle materials are subjected to applied down force and shear load in the presence of chemically active aqueous solutions. This harsh process not only increases the k value but also mechanically damages the thin-films. In this study, we demonstrate the role of surfactants, which are essential components of the CMP slurry, on the solution diffusion in nanoporous organosilicate thin-films. Surfactants were found to enhance the diffusion significantly depending on hydrophobic/hydrophilic group lengths and the structure of the surfactant molecule. Direct evidence of surfactant penetration was obtained using x-ray photoelectron spectroscopy after ion etching. We propose a possible diffusion mechanism using the polymer reptation model to explain surfactant penetration in the nanoporous glass network. Finally, the implication of surfactant diffusion on an optimized CMP process in terms of k value requirements is presented.

Welding International, 2013

Bondability of Cu wire on Cu substrate with Sn plating by ultrasonic by FUJIWARA Shinichi and DAU... more Bondability of Cu wire on Cu substrate with Sn plating by ultrasonic by FUJIWARA Shinichi and DAUSKARDT Reinhold H. This study evaluated both the joint strength of copper wire on a copper substrate with tin plating and the joint reliability of copper wire bonding after heat treatment. The suitable tin thickness and bonding conditions, which are stage temperature, wire bonding power and bonding time, were chosen by the peel test after copper wire bonding. Tin thickness of 10 microns showed a high bonding rate under the conditions of stage temperature 373 K, bonding power 500 to 700 mW and bonding time 30 to 50 ms. Before heat treatment, the peel strength of the copper wire on the copper substrate with tin plating conditions was weaker than that of gold wire on a gold substrate. After heat treatment for more than 70 hours at 298 K, the peel strength of the copper wire became higher than that of the gold wire and twice as high as the initial bonding strength. The tin layer remained between the copper wire and copper substrate before heat treatment. When the samples were held at 298 K, tin reacted with copper and turned into a Cu-Sn intermetallic compound. Upon completion of this reaction at 298 K for over 70 hours, the soft tin layer between the copper wire and copper substrate disappeared. Therefore, the peel strength of copper wire after heat treatment increased. These results were observed by SEM images of the interface between the copper wire and copper substrate before and after heat treatment.

Nature Communications, 2014

Pressure sensing is an important function of electronic skin devices. The development of pressure... more Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultrasensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1 Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.