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Biosens Bioelectron ; 168: 112569, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32905930


Wearable and implantable bio-integrated electronics have started to gain momentum because of their essential role in improving the quality of life for various patients and healthy individuals. However, their continuous operation is often limited by traditional battery technologies with a limited lifespan, creating a significant challenge for their development. Thus, it is highly desirable to harvest biomechanical energies from human motion for self-powered bio-integrated functional devices. Piezoelectric energy harvesters are ideal candidates to achieve this goal by converting biomechanical energy to electric energy. Because of their applications on soft and highly deformable tissues of the human body, these devices also need to be mechanically flexible and stretchable, thus posing a significant challenge. Effective methods to address the challenge include the exploration of new stretchable piezoelectric materials (e.g., hybrid composite material) and stretchable structures (e.g., buckled shapes, serpentine mesh layouts, kirigami designs, among others). This review presents an overview of the recent developments in new intrinsically stretchable piezoelectric materials and rigid inorganic piezoelectric materials with novel stretchable structures for flexible and stretchable piezoelectric sensors and energy harvesters. Following the discussion of theoretical modeling of the piezoelectric materials to convert mechanical deformations into electrical signals, the representative applications of stretchable piezoelectric materials and structures in wearable and implantable devices are briefly summarized. The present limitations and future research directions of flexible and stretchable piezoelectric devices are then discussed.

Nanomaterials (Basel) ; 9(2)2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30781651


Flexible electronic systems have received increasing attention in the past few decades because of their wide-ranging applications that include the flexible display, eyelike digital camera, skin electronics, and intelligent surgical gloves, among many other health monitoring devices. As one of the most widely used technologies to integrate rigid functional devices with elastomeric substrates for the manufacturing of flexible electronic devices, transfer printing technology has been extensively studied. Though primarily relying on reversible interfacial adhesion, a variety of advanced transfer printing methods have been proposed and demonstrated. In this review, we first summarize the characteristics of a few representative methods of transfer printing. Next, we will introduce successful demonstrations of each method in flexible electronic devices. Moreover, the potential challenges and future development opportunities for transfer printing will then be briefly discussed.

Sci Rep ; 8(1): 6684, 2018 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-29703923


We use in situ scanning probe microscopy (SPM) to investigate the high temperature oxidation of Ni-based single crystal alloys at the micro-/nanoscale. SiO2 micro-pillar arrays were pre-fabricated on the alloy surface as markers before the oxidation experiment. The SPM measurement of the oxidized surface in the vicinity of SiO2 micro-pillars was conducted real time at temperatures from 300 °C to 800 °C. The full-field evolution of oxide film thickness is quantitatively characterized by using the height of SiO2 micro-pillars as reference. The results reveal the non-uniform oxide growth featuring the nucleation and coalescence of oxide islands on the alloy surface. The outward diffusion of Ni and Co is responsible for the formation and coalescence of first-stage single-grain oxide islands. The second-stage of oxidation involves the formation and coalescence of poly-grain oxide islands.

Adv Mater ; 24(16): 2117-22, 2012 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-22431430


In this paper we present mechanics and materials aspects of elastomeric stamps that have angled features of relief on their surfaces, designed to enable control of adhesion strength by peeling direction, in a way that can be exploited in schemes for deterministic assembly by transfer printing. Detailed mechanics models capture the essential physics of interface adhesion in this system. Experiments with cylindrical stamps that have this design demonstrate their potential for use in a continuous, roller mode of operation.

Adesivos/química , Elastômeros/química , Impressão/métodos , Propriedades de Superfície