ORCID Profile
0000-0002-1200-6456
Current Organisation
Indian Institute of Technology Delhi
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Publisher: Springer Science and Business Media LLC
Date: 22-09-2022
DOI: 10.1038/S41467-022-33234-8
Abstract: Cooling in buildings is vital to human well-being but inevitability consumes significant energy, adding pressure on achieving carbon neutrality. Thermally superinsulating aerogels are promising to isolate the heat for more energy-efficient cooling. However, most aerogels tend to absorb the sunlight for unwanted solar heat gain, and it is challenging to scale up the aerogel fabrication while maintaining consistent properties. Herein, we develop a thermally insulating, solar-reflective anisotropic cooling aerogel panel containing in-plane aligned pores with engineered pore walls using boron nitride nanosheets by an additive freeze-casting technique. The additive freeze-casting offers highly controllable and cumulative freezing dynamics for fabricating decimeter-scale aerogel panels with consistent in-plane pore alignments. The unique anisotropic thermo-optical properties of the nanosheets combined with in-plane pore channels enable the anisotropic cooling aerogel to deliver an ultralow out-of-plane thermal conductivity of 16.9 mW m −1 K −1 and a high solar reflectance of 97%. The excellent dual functionalities allow the anisotropic cooling aerogel to minimize both parasitic and solar heat gains when used as cooling panels under direct sunlight, achieving an up to 7 °C lower interior temperature than commercial silica aerogels. This work offers a new paradigm for the bottom-up fabrication of scalable anisotropic aerogels towards practical energy-efficient cooling applications.
Publisher: Wiley
Date: 10-11-2021
Abstract: A key challenge in textile sensors is to adequately solve the hysteresis for more broad and exacting applications. Unlike the conventional strategy in integrating elastic polymers into the textile, the hysteretic issue is critically addressed here through the structural design of yarns to provide a twisting force. The underlying mechanism is fully discussed based on theory and modeling, which are in good agreement with experimental data. Impressively, the pressure sensor outperforms almost all reported textile‐based sensors in terms of recovery index, which refers to the ability to overcome the lagged deformation reflected by the hysteresis (5.3%) and relaxation time (2 ms). Besides, the sensor superiority is also demonstrated by way of its ultrafast response time (2 ms). Thanks to these merits, this pressure sensor is demonstrated to be capable of monitoring epidermal pulses and meanwhile shows great potential to advance the standardization and modernization of pulse palpation in traditional Chinese medicine.
Publisher: Wiley
Date: 17-09-2022
Abstract: Electronic skins (e‐skins) mimic multimodal sensing capabilities of various tactile receptors in natural skin. Herein, a stretchable chromotropic ionic skin is rationally designed to simultaneously detect and decouple multiple stimuli, including in‐plane strain, temperature, and pressure. The mutually discriminating trimodal ionic skin consists of mechanochromic, thermoresistive and triboelectric layers that in idually function as strain, temperature and pressure sensors, respectively. These three distinct capabilities are integrated into the ionic skin which demonstrates highly sensitive responses to selective external stimuli while upholding high insensitivity to unwanted ones. The structural colors derived from mechanochromic photonic crystals of magnetic ferroferric oxide‐carbon nanoparticles respond to strains by color‐switching in the full visible spectrum, exhibiting appealing potential in interactive stress visualization. The temperature detection with an exceptional sensitivity of 20.44% per °C is enabled by the thermoresistive effect of ionic hydrogel, while oriented polymer chains embedded in the hydrogel decouple temperature from extraneous stimuli. The multilayer structure consisting of an ionic hydrogel film, a wrinkle‐patterned polydimethylsiloxane (PDMS) film with gradient modulus design and a carbon nanotubes/PDMS electrode displays an extraordinary triboelectric effect with a strain‐ and temperature‐insensitive pressure sensing capability. The chromotropic ionic skin facilitates simultaneously accurate measurements, high discriminability and quantitative mapping of complex stimuli, offering new insights into emerging E‐skins.
Publisher: Springer Science and Business Media LLC
Date: 02-02-2022
DOI: 10.1007/S40820-022-00797-6
Abstract: With the mandate of worldwide carbon neutralization, pursuing comfortable living environment while consuming less energy is an enticing and unavoidable choice. Novel composite aerogels with super thermal insulation and high sunlight reflection are developed for energy-efficient buildings. A solvent-assisted freeze-casting strategy is used to produce boron nitride nanosheet olyvinyl alcohol (BNNS/PVA) composite aerogels with a tailored alignment channel structure. The effects of acetone and BNNS fillers on microstructures and multifunctional properties of aerogels are investigated. The acetone in the PVA suspension enlarges the cell walls to suppress the shrinkage, giving rise to a lower density and a higher porosity, accompanied with much diminished heat conduction throughout the whole product. The addition of BNNS fillers creates whiskers in place of disconnected transverse ligaments between adjacent cell walls, further ameliorating the thermal insulation transverse to the cell wall direction. The resultant BNNS/PVA aerogel delivers an ultralow thermal conductivity of 23.5 mW m −1 K −1 in the transverse direction. The superinsulating aerogel presents both an infrared stealthy capability and a high solar reflectance of 93.8% over the whole sunlight wavelength, far outperforming commercial expanded polystyrene foams with reflective coatings. The anisotropic BNNS/PVA composite aerogel presents great potential for application in energy-saving buildings.
Publisher: Wiley
Date: 05-10-2021
Abstract: A rational approach is proposed to design soft multifunctional sensors capable of detection and discrimination of different physical stimuli. Herein, a flexible multifunctional sensor concurrently detecting and distinguishing minute temperature and pressure stimuli in real time is developed using electrospun carbon nanofiber (CNF) films as the sole sensing material and electrical resistance as the only output signal. The stimuli sensitivity and discriminability are coordinated by tailoring the atomic‐ and device‐level structures of CNF films to deliver outstanding pressure and temperature sensitivities of − 0.96 kPa −1 and − 2.44% ° C −1 , respectively, enabling mutually exclusive sensing performance without signal cross‐interference. The CNF multifunctional sensor is considered the first of its kind to accomplish the stimulus discriminability using only the electrical resistance as the output signal, which is most convenient to monitor and process for device applications. As such, it has distinct advantages over other reported sensors in its simple, cost‐effective fabrication and readout system. It also possesses other invaluable traits, including good bending stability, fast response time, and long‐term durability. Importantly, the ability to simultaneously detect and decouple temperature and pressure stimuli is demonstrated through novel applications as a skin‐mountable device and a flexible game controller.
No related grants have been discovered for Harun VENKATESAN.