Measurement of the Deeply Virtual Compton Scattering Cross Section from the Proton at 10.6 GeV using the CLAS12 Detector

Deeply Virtual Compton Scattering (DVCS) is an exclusive process that produces a real photon when a lepton scatters from a quark inside a nucleon or a nucleus. Measurement of the DVCS cross section enables the study of the Generalized Parton Distributions (GPD), which plays a central role in understanding the QCD dynamics inside a hadron. Thus, the quark and gluon origin of the nucleon spin and mass can be probed and three-dimensional images of the target nucleon or nucleus can be realized. This thesis presents a cross section analysis of DVCS from the proton in the presence of its background, Bethe-Heitler (BH) process. The CEBAF Large Acceptance Spectrometer for operation at 12 GeV beam en-ergy (CLAS12) collaboration has taken electron-proton scattering data in fall 2018 using a liquid hydrogen target and the 10.6 GeV polarized electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF). The CLAS12 detector is a nearly hermetic fixed-target detector, located in Hall B, Jefferson Lab at Newport News, Virginia. The experimentally determined BH-DVCS cross section is in good agreement with a phenomenological-model based theoretical prediction. The kinematic dependence of the cross section is reported over a wide range. The short-term plan to utilize the results presented here for a thorough tomography study and the long-term plan for GPD studies at future facilities such as the Electron-Ion Collider (EIC) are discussed.Ph.D

Fully laser-patterned stretchable microsupercapacitors integrated with soft electronic circuit components

Stretchable energy storage devices are prerequisites for the realization of autonomous elastomeric electronics. Microsupercapacitors (MSCs) are promising candidates for this purpose due to their high power and energy densities, potential for miniaturization, and feasibility of embedding in circuits; however, efforts to realize stretchable MSCs have mostly relied on strain-accommodating materials and have suffered from limited stretchability, low conductivity, or complicated patterning processes. Here, we designed and fabricated a stretchable MSC based on reduced-graphene-oxide/Au heterostructures patterned by facile and versatile direct laser patterning. An interconnected and stable 3D network composed of vertically oriented heterostructures was realized by high-repetition-rate femtosecond laser pulses. Upon transferring to polydimethylsiloxane (PDMS), the 3D network achieved a high conductivity of ~105 S m−1, and the conductivity could be maintained at ~104 S m−1 even at 50% strain. A fully laser-patterned stretchable electronics system was integrated with embedded MSCs, which will find applications in soft robotics, wearable electronics, and the Internet of Things.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio

Inkjet-printed metal oxide nanoparticles on elastomer for strain-adaptive transmissive electrochromic energy storage systems

The emergence of soft energy devices provides new possibilities for various applications, it also creates significant challenges in the selection of structural design and material compatibility. Herein, we demonstrate a stretchable transmissive electrochromic energy storage device by inkjet-printing single layer of WO3 nanoparticles on an elastomeric transparent conductor. Such hybrid electrode is highly conductive and deformable, making it an excellent candidate for the application: large optical modulation of 40%, fast switching speed (<4.5 s), high coloration efficiency (75.5 cm2 C−1), good stability and high specific capacity (32.3 mAh g−1 and 44.8 mAh cm−3). The device consists of WO3-based hybrid electrode and polyaniline/carbon nanotubes composite electrode. It maintains excellent electrochromic and energy storage performance even when stretched up to 50%, and achieves a maximum areal energy density of 0.61 μWh cm−2 and power density of 0.83 mW cm−2, which is one of the highest values in stretchable transparent energy storage devices. A device featuring stretchable transparent nanowires based electrode is illustrated as an energy indicator in which the stored energy can be monitored via reversible color variation. This high performance and multifunctional electrochromic energy storage device is a promising candidate for deformable and wearable electronics

Coaxial Ag–Base Metal Nanowire Networks with High Electrochemical Stability for Transparent and Stretchable Asymmetric Supercapacitors

Transparent and stretchable Ag–Ni and Ag–Fe core–shell nanowire networks were fabricated as a cathode and anode, respectively, for asymmetric supercapacitors. Both electrodes showed a reversible stretchability at up to 100% strain and exhibited high electrochemical stability and specific capacitances of ∼3 mF cm−2 with 50% optical transmittance. The asymmetric device assembled with a PVA/KOH electrolyte demonstrated a high operating voltage of 1.6 V and an excellent capacitance retention (92%) over 5000 cycles even after stretching to 35% strain.NRF (Natl Research Foundation, S’pore)Accepted versio

Multi-responsive supercapacitors : smart solution to store electrical energy

With increasing demand for economic and eco-friendly energy conversion and storage system, smart devices integrating both energy conversion and storage have received increasing attention as a key breakthrough for efficient energy utilization. In recent years, significant attempts are made in the integration of the two technologies taking all possible means into account to convert energy efficiently. Among the options, multi-responsive supercapacitors which can be charged using diverse renewable resources, e.g. mechanical force, temperature or light, are widely considered as a promising energy integrated system because of the unique characteristics of supercapacitors, such as fast charging/discharging rate, high power density, simple configuration. In this review, we provide insights into the mechanism of converting mechanical force, temperature and light into electrochemical energy. We shed light on various alternatives to store electrical energy using an electrochemical energy storage unit to realize multi-responsive supercapacitors. In addition, other means of enabling electrochemical energy storage are also discussed in brief. The challenges of the integrated system for simultaneous realization of energy conversion and storage are highlighted.NRF (Natl Research Foundation, S’pore)Accepted versio

Ultrafast Laser Pulses Enable One‐Step Graphene Patterning on Woods and Leaves for Green Electronics

Fast, simple, cost-efficient, eco-friendly, and design-flexible patterning of high-quality graphene from abundant natural resources is of immense interest for the mass production of next-generation graphene-based green electronics. Most electronic components have been manufactured by repetitive photolithography processes involving a large number of masks, photoresists, and toxic etchants; resulting in slow, complex, expensive, less-flexible, and often corrosive electronics manufacturing processes to date. Here, a one-step formation and patterning of highly conductive graphene on natural woods and leaves by programmable irradiation of ultrafast high-photon-energy laser pulses in ambient air is presented. Direct photoconversion of woods and leaves into graphene is realized at a low temperature by intense ultrafast light pulses with controlled fluences. Green graphene electronic components of electrical interconnects, flexible temperature sensors, and energy-storing pseudocapacitors are fabricated from woods and leaves. This direct graphene synthesis is a breakthrough toward biocompatible, biodegradable, and eco-friendlily manufactured green electronics for the sustainable earth.National Research Foundation (NRF)T.-S.D.L. and S.P. contributed equally to this work. This work was supported by the NRF-Investigatorship, Award No. NRF-NRFI2016-05. This work was also supported by an NRF Fellowship (NRF-NRFF2015-02) from the Singapore National Research Foundation