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1. Zero‐standby power hydrogen sensing using event‐driven micromechanical switches

   https://doi.org/10.1002/rpm2.70018  

   Jahadun_Nobi, S_M; Herrmann, Eric; Huang, Zhixiang; Sitaram, Sai Rahul; Laskowski, Kyle; Wang, Xi (August 2025, Responsive Materials)

   Abstract Zero‐standby power sensors are crucial for enhancing the safety and widespread adoption of hydrogen (H₂) technologies in chemical processes and sustainable energy applications, given the flammability of H₂at low concentrations. Here, we report an event‐driven hydrogen sensing system utilizing palladium (Pd)‐based micromechanical cantilever switches. The detection mechanism relies on strain generation in the Pd layer, which undergoes reversible volume expansion upon hydrogen adsorption. Our experimental and simulation results demonstrate that the bistable micromechanical switch‐based sensor generates a wake‐up signal with activation time depending on hydrogen concentration in the target environment while always remaining active for events without any standby power consumption under normal conditions. The H₂adsorption‐induced subsequent switching of the multi‐cantilever‐based switch configuration on the sensor resulted in the quasi‐quantification of hydrogen concentrations. The reported zero‐standby power sensor's operational lifetime is limited by the frequency of detection events and exposure to concentrations exceeding hydrogen's flammability limit. This work advances the development of high‐density, maintenance‐free sensor networks for large‐scale deployment with Internet of Things devices, enabling unattended continuous monitoring of hydrogen generation, transportation, distribution, and end‐user applications. 

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2. Engineering defects with DNA

   https://doi.org/10.1126/science.abq2580  

   Wang, YuHuang (July 2022, Science)

   Strategically introduced defects can be used to modify carbon nanotubes for new properties and functions. For example, chemical defects can act as atomic traps for electrons, holes, electron-hole pairs, and even molecules and ions ( 1 ). The ability to control the placement of these defects on carbon nanotubes could enable a plethora of fundamental studies and potential applications in imaging, sensing, disease diagnostics, and quantum information science ( 2 – 4 ). However, there is yet no effective way to do this with atomic precision ( 5 – 7 ). On page 535 of this issue, Lin et al. ( 8 ) report the creation of ordered defect arrays by programming DNA strands to wrap around and traverse the entire length of a single-walled carbon nanotube. 

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3. Aligned 2D carbon nanotube liquid crystals for wafer-scale electronics

   https://doi.org/10.1126/sciadv.abh0640  

   Jinkins, Katherine R.; Foradori, Sean M.; Saraswat, Vivek; Jacobberger, Robert M.; Dwyer, Jonathan H.; Gopalan, Padma; Berson, Arganthaël; Arnold, Michael S. (September 2021, Science Advances)

   Semiconducting carbon nanotubes promise faster performance and lower power consumption than Si in field-effect transistors (FETs) if they can be aligned in dense arrays. Here, we demonstrate that nanotubes collected at a liquid/liquid interface self-organize to form two-dimensional (2D) nematic liquid crystals that globally align with flow. The 2D liquid crystals are transferred onto substrates in a continuous process generating dense arrays of nanotubes aligned within ±6°, ideal for electronics. Nanotube ordering improves with increasing concentration and decreasing temperature due to the underlying liquid crystal phenomena. The excellent alignment and uniformity of the transferred assemblies enable FETs with exceptional on-state current density averaging 520 μA μm −1 at only −0.6 V, and variation of only 19%. FETs with ion gel top gates demonstrate subthreshold swing as low as 60 mV decade −1 . Deposition across a 10-cm substrate is achieved, evidencing the promise of 2D nanotube liquid crystals for commercial semiconductor electronics. 

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4. Parameters Affecting Interfacial Assembly and Alignment of Nanotubes

   https://doi.org/10.1021/acs.langmuir.3c02000  

   Jinkins, Katherine R.; Dwyer, Jonathan H.; Suresh, Anjali; Foradori, Sean M.; Gopalan, Padma; Arnold, Michael S. (October 2023, Langmuir)

   Tangential flow interfacial self-assembly (TaFISA) is a promising scalable technique enabling uniformly aligned carbon nanotubes for high-performance semiconductor electronics. In this process, flow is utilized to induce global alignment in two-dimensional nematic carbon nanotube assemblies trapped at a liquid/liquid interface, and these assemblies are subsequently deposited on target substrates. Here, we present an observational study of experimental parameters that affect the interfacial assembly and subsequent aligned nanotube deposition. We specifically study the water contact angle (WCA) of the substrate, nanotube ink composition, and water subphase and examine their effects on liquid crystal defects, overall and local alignment, and nanotube bunching or crowding. By varying the substrate chemical functionalization, we determine that highly aligned, densely packed, individualized nanotubes deposit only at relatively small WCA between 35 and 65°. At WCA (< 10°), high nanotube bunching or crowding occurs, and the film is nonuniform, while aligned deposition ceases to occur at higher WCA (>65°). We find that the best alignment, with minimal liquid crystal defects, occurs when the polymer-wrapped nanotubes are dispersed in chloroform at a low (0.6:1) wrapper polymer to nanotube ratio. We also demonstrate that modifying the water subphase through the addition of glycerol not only improves overall alignment and reduces liquid crystal defects but also increases local nanotube bunching. These observations provide important guidance for the implementation of TaFISA and its use toward creating technologies based on aligned semiconducting carbon nanotubes. 

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5. Substrate‐Wide Confined Shear Alignment of Carbon Nanotubes for Thin Film Transistors

   https://doi.org/10.1002/aelm.201800593  

   Jinkins, Katherine_R; Chan, Jason; Jacobberger, Robert_M; Berson, Arganthaël; Arnold, Michael_S (November 2018, Advanced Electronic Materials)

   Abstract To exploit their charge transport properties in transistors, semiconducting carbon nanotubes must be assembled into aligned arrays comprised of individualized nanotubes at optimal packing densities. However, achieving this control on the wafer‐scale is challenging. Here, solution‐based shear in substrate‐wide, confined channels is investigated to deposit continuous films of well‐aligned, individualized, semiconducting nanotubes. Polymer‐wrapped nanotubes in organic ink are forced through sub‐mm tall channels, generating shear up to 10 000 s⁻¹uniformly aligning nanotubes across substrates. The ink volume and concentration, channel height, and shear rate dependencies are elucidated. Optimized conditions enable alignment within a ±32° window, at 50 nanotubes µm⁻¹, on 10 × 10 cm²substrates. Transistors (channel length of 1–5 µm) are fabricated parallel and perpendicular to the alignment. The parallel transistors perform with 7× faster charge carrier mobility (101 and 49 cm²V⁻¹s⁻¹assuming array and parallel‐plate capacitances, respectively) with high on/off ratio of 10⁵. The spatial uniformity varies ±10% in density, ±2° in alignment, and ±7% in mobility. Deposition occurs within seconds per wafer, and further substrate scaling is viable. Compared to random networks, aligned nanotube films promise to be a superior platform for applications including sensors, flexible/stretchable electronics, and light emitting and harvesting devices. 

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