There is a growing trend to apply field emission (FE) electron sources in vacuum electronic devices due to their fast response, high efficiency and low energy consumption compared to thermionic emission ones. Carbon nanotubes (CNTs) have been regarded as a promising class of electron field emitters since the 1990s and have promoted the development of FE technology greatly because of their high electrical and thermal conductivity, chemical stability, high aspect ratio and small size. Recent studies have shown that FE from CNTs has the potential to replace conventional thermionic emission in many areas and that it exhibits advanced features in practical applications. Consequently, FE from nanotubes and applications thereof have attracted much attention. This paper provides a comprehensive review of both recent advances in CNT field emitters and issues related to applications of CNT based FE. FE theories and principles are introduced, and the early development of field emitters is related. CNT emitter types and their FE performance are discussed. The current situation for applications based on nanotube FE is reviewed. Although challenges remain, the tremendous progress made in CNT FE over the past ten years indicates the field's development potential.
People with quadriplegia have a high risk for respiratory illness, social isolation and depression. Previous research has demonstrated that therapeutic singing interventions can not only improve breathing function and speech loudness, but also improve mood and social connectedness for people with quadriplegia. Face-to-face group attendance is difficult for this population due to difficulties with distance and travel. Online environments offer an accessible and cost-effective solution for people to connect with others without leaving their home. In a two-phase iterative design, we explored and tested different approaches for delivering online music therapy sessions with 12 patients from an inpatient spinal cord injury rehabilitation service. Six participants in Phase 1 trialled different virtual reality headsets and completed a short interview about their experience of the equipment and online singing trials. Outcomes from Phase 1 testing led to the development of a custom-built virtual reality application for online group music therapy sessions with low-latency audio. We tested the acceptability and feasibility of this platform in comparison to face-to-face and teleconference options for music therapy with six different patients. These participants completed three validated questionnaires: System Usability Scale, Quebec User Evaluation of Satisfaction with assistive Technology, and Psychosocial Impact of Assistive Devices Scale, and an interview about their experience. Questionnaire scores were good with mean ratings of 4.4 for Quebec User Evaluation of Satisfaction with assistive Technology, 53 for System Usability Scale and positive mean Psychosocial Impact of Assistive Devices Scale scores of 1.5 for competence, 2 for adaptability and 1.5 for self-esteem. Thematic analysis of post-session qualitative interviews revealed five themes: virtual reality was a positive experience, virtual reality was immersive and transportative, virtual reality reduced inhibitions about singing in front of others, virtual reality may reduce social cues, and the virtual reality equipment was comfortable, accessible and easy to use. Telehealth options, including a custom-designed virtual reality program, with low-latency audio are an acceptable and feasible mode of delivery for therapeutic singing interventions for people with spinal cord injury. Future non-inferiority research is needed to test online delivery modes for music therapy in comparison to face-to-face treatment.
Field emission (FE) uniformity and the mechanism of emitter failure of freestanding carbon nanotube (CNT) arrays have not been well studied due to the difficulty of observing and quantifying FE performance of each emitter in CNT arrays. Herein a field emission microscopy (FEM) method based on poly(methyl methacrylate) (PMMA) thin film is proposed to study the FE uniformity and CNT emitter failure of freestanding CNT arrays. FE uniformity of freestanding CNT arrays and different levels of FE current contributions from each emitter in the arrays are recorded and visualized. FEM patterns on the PMMA thin film contain the details of the CNT emitter tip shape and whether multiple CNT emitters occur at an emission site. Observation of real-time FE performance and the CNT emitter failure process in freestanding CNT arrays are successfully achieved using a microscopic camera. High emission currents through CNT emitters causes Joule heating and light emission followed by an explosion of the CNTs. The proposed approach is capable of resolving the major challenge of building the relationship between FE performance and CNT morphologies, which can significantly facilitate the study of FE non-uniformity, the emitter failure mechanism and the development of stable and reliable FE devices in practical applications.
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