Symposium SB03—Robotic Materials for Advanced Machine Intelligence

Jordan Raney, University of Pennsylvania

Electronics-Free Soft Robot with Multi-Stimuli Responsive Control

Written by Corrisa Heyes

Jordan Raney presents a nematic soft robot that can respond to environmental conditions autonomously. The robot moves mechanically and turns in response to the presence of light, heat, and/or solvents. This autonomous movement is achieved by incorporating responsive material features to the robot soft body. Furthermore, simple logic gate computation is achieved by including additional features. This is an impressive first step toward fully autonomous robotics with sensing and response capabilities without electronics. Applications for this technology encompass adverse environmental conditions where a traditional electronic robot cannot perform (e.g., electromagnetic interference) or long-term missions (e.g., send to Mars) where power generation is prohibitively expensive. 

Symposium NM01—Beyond Graphene 2D Materials—Synthesis, Properties and Device Applications

Young Hee Lee, Sungkyunkwan University, and IBS Center for Integrated Nanostructure Physics

van der Waals Layered Magnetic Semiconductors

Written by Mohit Saraf 

Young Hee Lee introduced two-dimensional (2D) van der Waals (vdW) transition metal dichalcogenides (TMDs) and explained their rich materials library and physics. He explained the properties of these 2D vdW such as strong coulombic interaction, reduced charge screening, and strong spin-orbit coupling. He also discussed about the history of diluted magnetic semiconductors. He said the key research target in this field is to realize the long-range order ferromagnetism and goals are gate modulation, long range magnetic ordering and Tc over room temperature. He discussed their chemical vapor deposition (CVD) work for V-doped WSe2 monolayer and explained some phenomenon such as V-site, their possible semiconductor nature, V-doping level, spin-selective exciton hole coupling, long-range magnetic ordering, spin modulation by gate-bias with magnetic force microscopy (MFM), defect induced magnetism, selenium (Se)-vacancies, transport with light, and trapping/de-trapping in Se vacancy states via grating. He concluded that Se vacancy itself provokes magnetic order due to strong spin-orbit coupling.

He also discussed about ferromagnetism via enriched Se-vacancy in V-WSe2, annealing temperature dependent magnetic ordering, atomic structure of annealed 0.5% V-doped WSe2, theoretical analyses, enhancement of magnetic moment via Se-vacancy, magnetic interaction of V. He discussed both theoretical and experimental work and said that V-dopant coupled with Se-vacancies escalate magnetic order and escalate Tc. The highlight of his talk was room-temperature ferromagnetism in monolayer TMDs and bulk materials.

Symposium NM06—Nanoscale Mass Transport Through 2D and 1D Nanomaterials

Mehrnaz Mojtabavi, Northeastern University 

Nanopores in Self-Assembled Monolayer-to-Multilayer MXene Films—From Fabrication to Application 

Written by Mohit Saraf 

Mehrnaz Mojtabavi highlighted the importance of nanopore technology that has gained wide attention in single-molecule studies of biomolecules. This technology provides an opportunity for sensing, manipulation, and sequencing of biopolymers such as DNA, RNA, and proteins. She discussed the importance of two-dimensional (2D) materials such as graphene, MoS2 in this emerging technology and introduced the promising candidature of MXenes in this area. She said that despite the robustness of this emerging technology, the sensing resolution is usually limited by pore thickness and access resistance. These issues can be addressed using MXenes-based technology as they are hydrophilic and possess excellent electrical conductivity. She used two MXenes, Ti3C2 and Ti2C, in her work and achieved promising results. She also introduced four MXenes-based approaches for nanopore technologies, that is, (i) single molecule sensing with MXene nanopores, (ii) water-scale MXene film fabrication and transfer, (iii) ionically active MXene nanopore actuators, and (iv) ion-fountain nanopore reader. She concluded by saying that 2D materials, particularly MXenes, are promising candidates for nanopore-based single molecule sensing, and development in this field will open new possibilities in the future.

Symposium EQ04—Advanced Soft Materials and Processing Concepts for Flexible Printed Optoelectronic Devices and Sensors

Elliot Strand, University of Colorado

Environmental Monitoring with Additively Manufactured Tattoo-Based Bioelectronics

Written by Corrisa Heyes

Traditional Internet of Things (IoT) environmental sensing devices have increased our ability to sustainably and effectively increase crop yield in an ever-shrinking agricultural environment. However, these sensors are prohibitively expensive to use at the desired scale. The answer: tattoos for plants! This work presents sub-micron thick bioelectronic sensors based on carbon capacitors printed on tattoo transfer paper in order to give our food source some stylish new art that can act to monitor environmental conditions in real-time and tap into the existing IoT networks for data reporting. Lab testing with simulated weather conditions gives the current integration of the sensor a lifespan measured in weeks, but the true test will be seeing how the new ink responds in the field. If they perform well, we could see a future where cornfields have sensing coverage measured in meters and cash crops can be monitored individually.

Symposium SF06—Recent Advances in Structural Materials from Bulk to Nanoscale

Heung Nam Han, Seoul National University

Neural Networks Approach to Correlate Plastic Properties with Indentation Data in Anisotropic Metals

Written by Corrisa Heyes

Heung Nam Han presents a combined finite element, neural network (FE-NN) method for modeling plasticity properties of anisotropic metals based on spherical and Knoop indentation. Tensile and plasticity testing is both high-cost and destructive of the sample. Conversely while instrumented indentation testing (IIT) has a reliability issue and numerical inverse analysis are generally computationally expensive, the marriage of the two has shown good agreement with uniaxial plastic curves from traditional tensile testing. This FE-NN method provides a robust modeling capability for IIT data. Knoop indentation is noted to be more effective than spherical due to the variability of measurements based on the associated indentation axis. While this work is currently focused specifically on single phase, anisotropic alloys, future work aims to expand to include a broader range of materials.

Symposium EQ03—Next-Generation Organic Semiconductors—Materials, Fundamentals and Applications

Jasmine Lim, University of Southern Mississippi

Attaining Infrared Detection in Devices with Narrow Bandgap Conjugated Polymers

Written by Corrisa Heyes

Most of the currently available visibility devices use epitaxial (inorganic crystals) semiconductors for their electronics; these options are expensive and require cooling apparatus. Conversely, organic materials (conjugated polymers) are low-cost and operate at room temperature. However, special attention is given to structural/electrical properties in order to avoid previously studied pitfalls to organics in IR detection applications. This first example of low bandgap polymers offers the desired functionality in broadband IR photodetection. Additionally, while organics are currently performing at the microsecond scale for response times (compared to nanosecond scale for inorganics), detection performance is on parr with commercially available inorganic systems. Future optimization study is expected to improve the current model beyond the performance of capabilities of inorganics.

Symposium EQ03—Next-Generation Organic Semiconductors—Materials, Fundamentals and Applications

Barry Thompson, University of Southern California

Reimagining Synthetic Approaches and Architectures for Semiconducting Polymers

Written by Corrisa Heyes

Try to go green! Barry Thompson presents a two-pronged proposal for decreasing environmental impact of generating conjugated polymers through increasing the sustainability of direct arylation polymerization (DArP). The conventional process involves the use of toxic solvents (toluene, xylenes, mesitylene, PhCl, etc.). Thompson proposes to use aromatic solvents like p-cymene (green!) which have a much higher boiling point, are not peroxide forming, and are very effective for conjugated polymer processes.  The conventional process involves (rare/expensive) palladium as a catalyst. First his research group thought to replace the palladium catalyst with copper; however, the use of a copper catalyst is not well enough understood. His further suggestions include a shift to a heterogeneous process in order to be able to reuse the palladium catalyst. Experimental data supports a 90%+ recyclability of the palladium when used with traditional solvents, which doesn’t work with p-cymene due to its non-polarity. In future work, Thompson’s group will address combining these proposed alternative options.

Symposium NM03—2D MXenes—Synthesis, Properties and Applications

Miladin Radovic, Texas A&M University

Safer MXene Synthesis Using Quaternary Ammonium Salts

Written by Mohit Saraf

Miladin Radovic introduced MXenes and all top-down strategies reported till date of producing them. He also explained the danger and toxicity associated with these approaches and then emphasized safer etching protocol that can produce single or few layer MXenes in aqueous solutions at room temperature. Radovic’s research team proposed a water-soluble tetraethylammonium fluoride tetrahydrate (TMAF) agent, which can work as etchant and intercalant at the same time. This technique removes an additional step of intercalation, and the yields were found to be similar to previously reported methods. The results were explained on Ti3C2 and Ti2C MXenes. The results open the possibility of using a range of quaternary ammonium salts in aqueous solutions for safer and scalable MXene synthesis.

Symposium NM03—2D MXenes—Synthesis, Properties and Applications

Kartik Nemani, Purdue University

High-Entropy 2D Carbide MXenes—TiVNbMoC3 and TiVCrMoC3

Written by Mohit Saraf

Kartik Nemani addressed the latest addition of high-entropy MXenes in the emerging growing family of MXenes. Researchers merged two different growing fields of high-entropy compounds and MXenes to come up with this new concept of high-entropy MXenes. Nemani and co-workers prepared two multi-principal-element high-entropy M4C3Tx MXenes, TiVNbMoC3Tx and TiVCrMoC3Tx as well as their precursor TiVNbMoAlC3 and TiVCrMoAlC3 high-entropy MAX phases. They studied these materials by x-ray diffraction, x-ray photoelectron spectroscopy, and energy dispersive x-ray spectroscopy to probe the phase composition and stoichiometry. They also used computational techniques to compute the formation energies. They evaluated the effect of entropic stabilization on the phase formation of the high-entropy MAX phases using non-equimolar transition metals such as Ti:V:Nb:Mo 1.3:1.3:1.3:0.1. This study expands the compositional diversity of MXenes and provides an opportunity to tailor their properties for numerous electronic, electrochemical, and catalytic, and other applications.

Symposium NM03—2D MXenes—Synthesis, Properties and Applications

Yury Gogotsi, Drexel University

Synthesis of 2D Transition Metal Carbides and Nitrides (MXenes)

Written by Mohit Saraf

Yury Gogotsi highlighted the importance of synthesis of MXenes from environmentally friendly, safe, efficient, and scalable methods. Typically, MXenes are synthesized from MAX phases by etching with acids (HF and HCl) followed by delamination. Their properties can be controlled by tuning their compositions and structures. They are hydrophilic, easily dispersible in water, strong, stiff and possess high electrical conductivity, making them suitable for a wide range of applications. However, the synthesis of MXenes may have some challenges such as use of HF acid, which is highly corrosive and dangerous for the human body and, therefore, the safety is equally important. This requires safety equipment which makes the overall synthesis process expensive. Therefore, safer, and environmentally stable synthesis is important. Gogotsi also emphasized the computational approaches of predicting the exfoliability of MAX phases. He said that different MXenes require different reaction parameters and therefore the exfoliation energy and etching parameters need to be adjusted and therefore the guidance from computational studies is important. He mentioned that stoichiometry of MXenes is also important and usually MXenes inherit the characteristics of MAX phases. The selective etching of MAX phases is important, and he discussed etching and delamination mechanisms. Gogotsi said that as per his knowledge, MXenes are the only nanomaterials which can be produced in kilogram of scale meaning true industrial scale applications can be addressed. Lastly, he mentioned several new MXene synthesis protocols coming up such as molten-salt synthesis which are relatively safer. Overall, he emphasized the simpler, safer, scalable, and environmentally stable synthesis of MXenes.