Co-reporter:Russell Kai Liang Tan;Sean P. Reeves;Niloofar Hashemi;Deepak George Thomas;Emrah Kavak;Nicole N. Hashemi
Journal of Materials Chemistry A 2017 vol. 5(Issue 34) pp:17777-17803
Publication Date(Web):2017/08/29
DOI:10.1039/C7TA05759H
In recent years, the technological advancement of supercapacitors has been increasing exponentially due to the high demand in electronic consumer products. As so, researchers have found a way to meet that demand by fabricating graphene. As developments are made toward the future, two big advancements to be made are large-scale fabrication of graphene and fabricating graphene as a flexible electrode. This would allow for use in larger products and for manipulation of the unique properties of graphene to accommodate superior design alternatives. While large scale production is still mentioned, this review is specifically focusing on different methods used to fabricate graphene as a flexible electrode. Various fabrication methods, such as Hummers' method, chemical vapor deposition, epitaxial growth, and exfoliation of graphite oxide, used to fabricate graphene in such a way that allows flexibility and utilization of graphene's mechanical and electrical properties are discussed. Additionally, a section on environmentally friendly fabrication approaches is presented and discussed.
Co-reporter:Wangyujue Hong, Abdallah Almomani, Reza Montazami
Measurement 2017 Volume 95(Volume 95) pp:
Publication Date(Web):1 January 2017
DOI:10.1016/j.measurement.2016.09.036
•Study of mechanoelectric response of ionic electroactive polymer (IEAP) sensors.•Study effect of the nanostructure of conductive network composite on attributes of IEAP sensors.•Achieved 3–4 folds increase in sensitivity of IEAP sensors.Ionic polymer metal composites (IPMCs) are the backbone of a wide range of ionic devices. IPMC mechanoelectric sensors are advanced nanostructured transducers capable of converting mechanical strain into easily detectable electric signal. Such attribute is realized by ion mobilization in and through IPMC nanostructure. In this study we have investigated electrochemical and morphological characteristics of IPMCs by varying the morphology of their metal composite component (conductive network composite (CNC)). We have demonstrated the dependence of electrochemical properties on CNC nanostructure as well as mechanoelectrical performance of IPMC sensors as a function of CNC morphology. It is shown that the morphology of CNC can be used as a means to improve sensitivity of IPMC sensors by 3–4 folds.
Co-reporter:Yuanfen Chen;Reihaneh Jamshidi;Wangyujue Hong;Nicole N. Hashemi
Advanced Engineering Materials 2017 Volume 19(Issue 8) pp:
Publication Date(Web):2017/08/01
DOI:10.1002/adem.201700139
Soft multilayer structures have broad applications in transient electronics. Strain-mismatch-induced fracture is key in achieving physical transiency. Here, swelling-mismatch-induced fragmentation of physically transient electrodes is studied. The fragment size of the electrode layer as a function of initial defect distribution is investigated. The average fragment size is predicted and verified by a combination of experimental and FEM analysis. It is found that only large defects initiate fragmentation; this concept can be used to control disintegration of physically transient electronics by means of materials and design, and can be extended to study transiency of soft multilayer structures.
Co-reporter:Simge Ç&x131;nar;Reihaneh Jamshidi;Yuanfen Chen;Nastaran Hashemi
Journal of Polymer Science Part B: Polymer Physics 2016 Volume 54( Issue 4) pp:517-524
Publication Date(Web):
DOI:10.1002/polb.23941
ABSTRACT
Transient electronics is a class of electronic devices designed to maintain stable operation for a desired and preset amount of time; and, undergo fast and complete degradation and deconstruction once transiency is triggered. Controlled and programmed transiency in solvent-triggered devices is strongly dependent on chemical and physical interactions between the solvent and the device, as well as those within the device itself, among its constituent components. Mechanics of transiency of prototypical transient circuits demonstrate strong dependence of the transiency characteristics on that of the substrate. In the present study, we demonstrate the control of transiency through the dissolution behavior of a substrate for the devices with electronic parts composed of colloidal units. It is observed that the physical circuit–substrate interactions are the dominating factors in defining the overall transiency behavior of the device. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 517–524
Co-reporter:Reihaneh Jamshidi;Simge Çinar;Yuanfen Chen;Nastaran Hashemi
Journal of Polymer Science Part B: Polymer Physics 2015 Volume 53( Issue 22) pp:1603-1610
Publication Date(Web):
DOI:10.1002/polb.23804
ABSTRACT
Transient soft bioelectronics are capable of forming conformal contacts with curvilinear surfaces of biological host tissues and organs. Such systems are often subject to continuous static and dynamic loads from the biological host. In this article, we present investigation of electronic attributes of transient soft bioelectronic circuits subjected to mechanical force and influence of substrate's transiency on the transiency of the whole device; also, characterize and quantify loss of functionality in triggered devices. Variations in the electrical conductivity of circuits as a function of applied mechanical load was used as a means to deduce electronic characteristics under stress. The experimental results suggest that there exists a correlation between electronic properties of circuits and applied mechanical strain; no clear correlation was, however, observed between electronic properties of circuits and frequency of the applied dynamic load. Control over transiency rate of identical circuits utilizing the transiency characteristics of the poly(vinyl alcohol)l-based substrates is also studied and demonstrated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1603–1610
Co-reporter:Han Acar;Simge Ç&x131;nar;Mahendra Thunga;Michael R. Kessler;Nastaran Hashemi
Advanced Functional Materials 2014 Volume 24( Issue 26) pp:4135-4143
Publication Date(Web):
DOI:10.1002/adfm.201304186
Controlled degradation and transiency of materials is of significant importance in the design and fabrication of degradable and transient biomedical and electronic devices and platforms. Here, the synthesis of programmable biodegradable and transient insulating polymer films is reported, which have sufficient physical and chemical properties to be used as substrates for the construction of transient electronics. The composite structure can be used as a means to control the dissolution and transiency rate of the polymer composite film. Experimental and computational studies demonstrate that the addition of gelatin or sucrose to a PVA polymer matrix can be used as a means to program and either slow or enhance the transiency of the composite. The dissolution of the polymer composites are fitted with inverse exponential functions of different time constants; the lower time constants are an indication of faster transiency of the polymer composite. The addition of gelatin results in larger time constants, whereas the addition of sucrose generally results in smaller time constants.
Co-reporter:Wangyujue Hong, Abdallah Almomani, Reza Montazami
Organic Electronics 2014 Volume 15(Issue 11) pp:2982-2987
Publication Date(Web):November 2014
DOI:10.1016/j.orgel.2014.08.036
•We investigated influence of IL content on performance of IEAP actuators.•Correlation between IL content and IEAP actuator performance is nonlinear.•Increasing IL content may result in formation of ionic double/multi-layers.•Ionic double/multi-layers deteriorate electromechanical response of IEAP actuators.We have investigated influence of ionic liquid concentration on the electromechanical response of ionic electroactive polymer actuators. Actuators were fabricated from ionomeric membrane and doped with different concentrations of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid. Samples were investigated for their electromechanical and electrochemical characteristics; and it was observed that the maximum electromechanical strain of approximately 1.4% is achieved at 22 wt% ionic liquid content. Increasing ionic liquid concentration results in saturation of the electrode–ionomer interface and formation of ionic double/multi layers, which in turn result an inward accumulation of ions; hence, generate strain in an undesired direction that deteriorates the electromechanical response of the actuator.Graphical abstract
Co-reporter:Reza Montazami, Christopher M. Spillmann, Jawad Naciri, Banahalli R. Ratna
Sensors and Actuators A: Physical 2012 Volume 178() pp:175-178
Publication Date(Web):May 2012
DOI:10.1016/j.sna.2012.01.026
Here we report the development of a thermomechanical nematic liquid crystal elastomer (LCE) actuator containing gold nanoparticles (AuNPs). Embedding a low concentration of AuNPs enhances the thermal conductivity of the actuator with minimal effect on the elasticity of the cross-linked polymer. Doping LCEs with AuNPs provides a means to improve the material response time to external stimuli. Under fast heating conditions, the AuNP-doped LCE actuators exhibited more than a 100% increase in the rate of change of strain with respect to time.