Manuela Loeblein

Configurable Three-Dimensional Boron Nitride–Carbon Architecture and Its Tunable Electronic Behavior with Stable Thermal Performances

Recent developments of 3D-graphene and 3D-boron-nitride have become of great interest owing to their potential for ultra-light flexible electronics. Here we demonstrate the first synthesis of novel 3D-BNC hybrids. By specifically controlling the compositions of C and BN, new fascinating properties are observed, such as highly tunable electrical conductivity, controllable EMI shielding properties, and stable thermal conductivity. This ultra-light hybrid opens up many new applications such as for electronic packaging and thermal interface materials (TIMs).

High-Density 3D-Boron Nitride and 3D-Graphene for High-Performance Nano–Thermal Interface Material

Compression studies on three-dimensional foam-like graphene and h-BN (3D-C and 3D-BN) revealed their high cross-plane thermal conductivity (62-86 W m-1 K-1) and excellent surface conformity, characteristics essential for thermal management needs. Comparative studies to state-of-the-art materials and other materials currently under research for heat dissipation revealed 3D-foams improved performance (20-30% improved cooling, temperature decrease by ΔT of 44-24 °C).

Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO2/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random and uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ∼25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ∼2 to 25...

3D Graphene-Infused Polyimide with Enhanced Electrothermal Performance for Long-Term Flexible Space Applications.

Polyimides (PIs) have been praised for their high thermal stability, high modulus of elasticity and tensile strength, ease of fabrication, and moldability. They are currently the standard choice for both substrates for flexible electronics and space shielding, as they render high temperature and UV stability and toughness. However, their poor thermal conductivity and completely electrically insulating characteristics have caused other limitations, such as thermal management challenges for flexible high-power electronics and spacecraft electrostatic charging. In order to target these issues, a hybrid of PI with 3D-graphene (3D-C), 3D-C/PI, is developed here. This composite renders extraordinary enhancements of thermal conductivity (one order of magnitude) and electrical conductivity (10 orders of magnitude). It withstands and keeps a stable performance throughout various bending and thermal cycles, as well as the oxidative and aggressive environment of ground-based, simulated space environments. This makes this new hybrid film a suitable material for flexible space applications.

Three‐Dimensional Graphene: A Biocompatible and Biodegradable Scaffold with Enhanced Oxygenation

Owing to its high porosity, specific surface area and three-dimensional structure, three-dimensional graphene (3D-C) is a promising scaffold material for tissue engineering, regenerative medicine as well as providing a more biologically relevant platform for living organisms in vivo studies. Recently, its differentiation effects on cells growth and anti-inflammation properties have also been demonstrated. Here, we report a complete study of 3D-C as a fully adequate scaffold for tissue engineering and systematically analyze its biocompatibility and biodegradation mechanism. The metabolic activities of liver cells (HepG2 hepatocarcinoma cells) on 3D-C are studied and our findings show that cell growth on 3D-C has high cell viability (> 90%), low lactate production (reduced by 300%) and its porous structure also provides an excellent oxygenation platform. 3D-C is also biodegradable via a 2-step oxidative biodegradation process by first, disruption of domains and lift off of smaller graphitic particles from the surface of the 3D-C and subsequently, the decomposition of these graphitic flakes. In addition, the speed of the biodegradation can be tuned with pretreatment of O2 plasma.

Human Rett-derived neuronal progenitor cells in 3D graphene scaffold as an in vitro platform to study the effect of electrical stimulation on neuronal differentiation

Studies of electrical stimulation therapies for the treatment of neurological disorders, such as deep brain stimulation, have almost exclusively been performed using animal-models. However, because animal-models can only approximate human brain disorders, these studies should be supplemented with an in vitro human cell-culture based model to substantiate the results of animal-based studies and further investigate therapeutic benefit in humans. This study presents a novel approach to analyze the effect of electrical stimulation on the neurogenesis of patient-induced pluripotent stem cell (iPSC) derived neural progenitor cell (NPC) lines, in vitro using a 3D graphene scaffold system. The iPSC-derived hNPCs used to demonstrate the system were collected from patients with Rett syndrome, a debilitating neurodevelopmental disorder. The graphene scaffold readily supported both the wild-type and Rett NPCs. Electrical stimulation parameters were optimized to accommodate both wild-type and Rett cells. Increased cell maturation and improvements in cell morphology of the Rett cells was observed after electrical stimulation. The results of the pilot study of electrical stimulation to enhance Rett NPCs neurogenesis were promising and support further investigation of the therapy. Overall, this system provides a valuable tool to study electrical stimulation as a potential therapy for neurological disorders using patient-specific cells.

Heat Dissipation Enhancement of 2.5D Package with 3D Graphene and 3D Boron Nitride Networks as Thermal Interface Material (TIM)

One of the major bottlenecks for the advancement in electronics is their heat dissipation. The exponential increase in packing density and computational power have resulted in a significant increase in power consumption and heat generation, such that thermal management in the new generation of microprocessor (i.e. 2.5D and 3D electronics) is starting to pose challenges in future development. These unwanted heat spots from the devices are typically extracted to the heat sink, via some thermal interface materials (TIMs). These TIMs build the important link between the heat source from the active region and the heat sink mounted on top. However, conventional TIMs are fast reaching their limits and innovative means are necessary to overcome thermal related challenges for the future generation. In this work, we present the nanostructured foam-like TIMs that are based on three-dimensional carbon (3D-C) and hexagonal boron nitride (3D-BN), with relatively high intrinsic thermal conductivities (~80 W/mK) and offer solution for both electrical conducting and insulating needs. Besides, these TIMs have ultra-high surface conformity, low weight, without the need of reflow or curing and are able to retain their high performance even at harsh environments of up to 700°C. Results on a 2.5D test chip show that these 3D foam-like TIMs have a reduction of temperature increase by 20% and of thermal resistance by 25%, significantly better than any conventional TIMs.

A “hairy” polymer/3D-foam hybrid for flexible high performance thermal gap filling applications in harsh environments

Thermal management in harsh environment electronics (i.e. automotive, avionics, oil and gas industry) has become a latent problem. Due to the more stringent requirements of the materials, such as higher operating temperatures, ability to operate under exposure to vibration and shock, and over larger gaps with complex paths, and increased demands in terms of reliability, the solutions adopted for consumer electronics cannot be directly translated into these applications and the current materials and approaches used are reaching their limits. Herein we present a new polymer/3D-foam composite that can fill large gaps and retain a thermal conductivity of 62–86 W m−1 K−1, while providing strong mechanical support with a strong restorative force (i.e. can withstand vibration). At the same time, it is demonstrated to have a superior surface conformity to usual gap fillers and is able to remain stable up to temperatures as high as 330 °C, which is ∼180 °C higher than current conventional packaging materials.