Sparsh Kapar

Microcapsulation of phase change materials (PCMs) within a shell is one of the most feasible methods to explore their applications for thermal energy storage. Here, a facile method to microencapsulate PCMs within polystyrene/cellulose nanocrystal (CNC) hybrid shell via Pickering emulsion polymerization was developed. CNCs, as biobased and sustainable materials hydrolyzed from wood pulp, were employed as emulsifiers of the PCM Pickering emulsion and shell components of the PCM microcapsules as well. CNCs displayed a high efficiency in the stabilization of paraffin wax (PW) Pickering emulsion, and the heat capacity and stability of PW microcapsules with CNC shell (PW@CNC) increased dramatically with the amounts of CNCs. PW microcapsules with polystyrene and CNC hybrid shell (PW@PS/CNC) were prepared via Pickering emulsion polymerization of styrene from the CNC stabilized PW Pickering emulsion droplets. The PW@PS/CNC slurries possessed a latent heat capacity of 31.9 J/g with stability as high as 99.4% after 100 heating and cooling scans. The PW@PS/CNC powder possessed a latent heat capacity of 160.3 J/g, corresponding to a high encapsulation ratio of 83.5%. Moreover, coconut oil (CO), as an example of biobased PCMs, was also microencapsulated within polystyrene and CNC hybrid shell (CO@PS/CNC) via a similar method. Both PW@PS/CNC and CO@PS/CNC slurries displayed excellent temperature regulation ability and offered promising potentials for thermal energy storage systems.

There is increasing interest in affordable and flexible electronics, driven by the need for displays, conformable body sensors, and internet-of-things (IoT) gadgets. Amorphous silicon (a-Si:H), transition metal oxides, and organic thin-film transistors (TFTs) have demonstrated cost-effective large-scale production. As TFTs are typically unipolar in nature, they pose challenges for implementing CMOS-like circuits. Conventional methods to realize circuits in these technologies often lead to restricted voltage swing and excessive direct path current. While several methods have been proposed to counter the voltage swing issue, these methods fail to address the direct path current problem. This article presents low static-power D flip-flops (DFFs) using unipolar TFTs, which significantly reduces the direct path current. The proposed and conventional DFF designs were fabricated on a glass and flexible substrate using a-Si:H TFTs. Additionally, the impact of bending the flexible substrates was examined to assess the robustness and performance of the DFFs under mechanical strain. The measurement results show that the proposed design based DFF saves average total power by 79.8% compared to conventional design.

Thin-film transistor (TFT) technology has demonstrated its effectiveness in large-area cost-efficient applications such as displays, flexible electronics, and medical devices. However, TFTs are typically unipolar in nature, and therefore, the realization of CMOS-like digital circuits is challenging. Traditional methods for implementing logic gates and complex circuits with unipolar TFT devices lead to high static power consumption and limited output swing. While various mitigation techniques have been developed, they fail to eliminate the direct path current problem in these circuits, which hinders static power reduction. The objective of this study is to address these issues and study its effect on flexible substrate.In this article, we propose logic gates that address these issues using a half-latch circuit. To demonstrate the concept, a 3-to-8 decoder was built using only n-type amorphous silicon (a-Si:H) TFTs on both glass and flexible substrates. We analyzed the impact of bending and substrate materials on the design. It was observed that the TFTs show an increase in current up to 8% under tensile stress, while a decrease in current up to 4% under compressive stress on flexible substrate. Measurements indicate that the proposed design reduces the average total power consumption of the 3-to-8 decoder by 46.5% compared to state-of-the-art techniques under various conditions.

There is growing interest in low-cost, low-thermal-budget electronics, particularly for displays, flexible body sensors, and affordable IoT devices. The potential of thin-film transistors (TFTs) in enabling these large-area, low-cost electronics has been proven. However, implementing complex circuits and on-chip SRAM with TFTs, which often lack complementary transistor types, poses challenges due to limited output swing, and excessive direct path current that leads to high power consumption. This paper introduces digital circuit designs that address these challenges. As a proof of concept, several key building blocks such as primary logic gates, decoders, and SRAM cells were fabricated using only n-type amorphous silicon (a-Si:H) TFTs on a glass and flexible substrate, and the impact of bending on circuit robustness was examined. The measurement results indicate that the proposed 2-to-4 decoder circuit maintains full output swing and reduces total average power consumption by 20.8compared to the state-of-the-art bootstrap circuit. Furthermore, the proposed SRAM cell reduces static power consumption by approximately 56× compared to a conventional 6T SRAM cell with unipolar TFTs.