scholarly journals Rational Design of Soft, Thermally Conductive Composite Liquid‐Cooled Tubes for Enhanced Personal, Robotics, and Wearable Electronics Cooling

2019 ◽  
Vol 4 (7) ◽  
pp. 1800690 ◽  
Author(s):  
Praveen Kotagama ◽  
Akshay Phadnis ◽  
Kenneth C. Manning ◽  
Konrad Rykaczewski
Keyword(s):  
Rational Design ◽  
Electronics Cooling ◽  
Wearable Electronics ◽  
Conductive Composite ◽  
Thermally Conductive ◽  
Personal Robotics

scholarly journals Anisotropic, Wrinkled, and Crack-Bridging Structure for Ultrasensitive, Highly Selective Multidirectional Strain Sensors

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Heng Zhang ◽  
Dan Liu ◽  
Jeng-Hun Lee ◽  
Haomin Chen ◽  
Eunyoung Kim ◽  
...  
Keyword(s):  
Rational Design ◽  
Full Range ◽  
Human Motion ◽  
Strain Sensors ◽  
Gauge Factor ◽  
Wearable Electronics ◽  
Trade Off ◽  
Human Motion Detection ◽  
Sensing Applications ◽  
Anisotropic Structures

AbstractFlexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications. Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities, existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity. Here, an ultrasensitive, highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers. The bilayer sensor consists of an aligned carbon nanotube (CNT) array assembled on top of a periodically wrinkled and cracked CNT–graphene oxide film. The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched, leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100% strain. The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3, to the benefit of accurate detection of loading directions by the multidirectional sensor. This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity, selectivity, and stretchability, demonstrating promising applications in full-range, multi-axis human motion detection for wearable electronics and smart robotics.

Thermal-Structural Performance of Orthotropic Pin Fin in Electronics Cooling Applications

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
A. F. M. Arif ◽  
Syed M. Zubair ◽  
S. Pashah
Keyword(s):  
Heat Sink ◽  
Structural Response ◽  
Electronics Cooling ◽  
Base Plate ◽  
Thermal Design ◽  
Heat Flow Rate ◽  
Thermal Interface ◽  
Conductive Composites ◽  
Thermally Conductive ◽  
As Stress

Thermally conductive composites as compared to metals have reduced density, decreased oxidation, and improved chemical resistance, as well as adjustable properties to fit a given application. However, there are several challenges that need to be addressed before they can be successfully implemented in heat sink design. The interface between the device and heat sink is an important factor in the thermal design of microelectronics cooling. Depending on the thermal interface conditions and material properties, the contact pressure and thermal stress level can attain undesirable values. In this paper, we investigate the effect of thermal interface between the fin and base plate on thermal-structural behavior of heat sinks. A coupled-field (thermal-structural) analysis using finite element method is performed to predict temperature as well as stress fields in the interface region. In addition temperature and heat flow rate predictions are supported through analytical results. effect of various interface geometrical (such as slot-depth, axial-gap, and radial-gap) and contact properties (such as air gap with surface roughness and gaps filled with interface material) on the resulting thermal-structural response is investigated with respect to four interface materials combinations, and it is found that the thermal performance is most sensitive to the slot-depth compared to any other parameter.

scholarly journals Polyaniline Nanofiber Wrapped Fabric for High Performance Flexible Pressure Sensors

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1120 ◽  
Author(s):  
Kangning Liu ◽  
Ziqiang Zhou ◽  
Xingwu Yan ◽  
Xiang Meng ◽  
Hua Tang ◽  
...  
Keyword(s):  
High Performance ◽  
Rational Design ◽  
Active Material ◽  
Pressure Sensors ◽  
Linear Range ◽  
Superior Performance ◽  
Wearable Electronics ◽  
Wide Linear Range ◽  
Polyaniline Nanofiber ◽  
Flexible Pressure Sensors

The rational design of high-performance flexible pressure sensors with both high sensitivity and wide linear range attracts great attention because of their potential applications in wearable electronics and human-machine interfaces. Here, polyaniline nanofiber wrapped nonwoven fabric was used as the active material to construct high performance, flexible, all fabric pressure sensors with a bottom interdigitated textile electrode. Due to the unique hierarchical structures, large surface roughness of the polyaniline coated fabric and high conductivity of the interdigitated textile electrodes, the obtained pressure sensor shows superior performance, including ultrahigh sensitivity of 46.48 kPa−1 in a wide linear range (<4.5 kPa), rapid response/relaxation time (7/16 ms) and low detection limit (0.46 Pa). Based on these merits, the practical applications in monitoring human physiological signals and detecting spatial distribution of subtle pressure are demonstrated, showing its potential for health monitoring as wearable electronics.

scholarly journals Material properties and structure of natural graphite sheet

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Martin Cermak ◽  
Nicolas Perez ◽  
Michael Collins ◽  
Majid Bahrami
Keyword(s):  
Material Properties ◽  
Coefficient Of Thermal Expansion ◽  
Electrical Contact ◽  
Sheet Thickness ◽  
Electronics Cooling ◽  
Forming Process ◽  
Electrical Contact Resistance ◽  
Natural Graphite ◽  
Graphite Sheet ◽  
Thermally Conductive

Abstract Natural graphite sheet (NGS) is compressible, porous, electrically and thermally conductive material that shows a potential to be used in fuel cells, flow batteries, electronics cooling systems, supercapacitors, adsorption air conditioning, and heat exchangers. We report the results of an extensive material characterization study that focuses on thermal conductivity, thermal diffusivity, electrical conductivity, coefficient of thermal expansion (CTE), compression strain, and emissivity. All the properties are density-dependent and highly anisotropic. Increasing the compression from 100 to 1080 kPa causes the through-plane thermal and electrical conductivities to increase by up to 116% and 263%, respectively. The properties are independent of the sheet thickness. Thermal and electrical contact resistance between stacked NGS is negligible at pressures 100 to 1080 kPa. In the in-plane direction, NGS follows the Wiedemann-Franz law with Lorenz number 6.6 $$\times $$ × 10$$^{-6}$$ - 6 W $$\Omega $$ Ω K$$^{-2}$$ - 2 . The in-plane CTE is low and negative (shrinkage with increasing temperature), while the through-plane CTE is high, increases with density, and reaches 33 $$\times $$ × 10$$^{-6}$$ - 6 K$$^{-1}$$ - 1 . Microscope images are used to study the structure and relate it to material properties. An easy-to-use graphical summary of the forming process and NGS properties are provided in Appendices A and B.

Thermal and Mechanical Modeling of Metal Foams for Thermal Interface Application

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Ninad Trifale ◽  
Eric Nauman ◽  
Kazuaki Yazawa
Keyword(s):  
Thermal Resistance ◽  
Metal Foam ◽  
Electronics Cooling ◽  
Cost Effective ◽  
Metal Foams ◽  
High Porosity ◽  
Pore Density ◽  
Thermal Interface ◽  
Interface Thermal Resistance ◽  
Thermally Conductive

We present a study on the apparent thermal resistance of metal foams as a thermal interface in electronics cooling applications. Metal foams are considered beneficial for several applications due to its significantly large surface area for a given volume. Porous heat sinks made of aluminum foam have been well studied in the past. It is not only cost effective due to the unique production process but also appealing for the theoretical modeling study to determine the performance. Instead of allowing the refrigerant flow through the open cell porous medium, we instead consider the foam as a thermal conductive network for thermal interfaces. The porous structure of metal foams is moderately compliant providing a good contact and a lower thermal resistance. We consider foam filled with stagnant air. The major heat transport is through the metal struts connecting the two interfaces with high thermally conductive paths. We study the effect of both porosity and pore density on the observed thermal resistance. Lower porosity and lower pore density yield smaller bulk thermal resistance but also make the metal foam stiffer. To understand this tradeoff and find the optimum, we developed analytic models to predict intrinsic thermal resistance as well as the contact thermal resistance based on microdeformation at the contact surfaces. The variants of these geometries are also analyzed to achieve an optimum design corresponding to maximum compliance. Experiments are carried out in accordance with ASTM D5470 standard. A thermal resistance between the range 17 and 5 K cm2/W is observed for a 0.125 in. thick foam sample tested over a pressure range of 1–3 MPa. The results verify the calculation based on the model consisting the intrinsic thermal conductivity and the correlation of constriction resistance to the actual area of contact. The area of contact is evaluated analytically as a function of pore size (5–40 PPI), porosity (0.88–0.95), orientation of struts, and the cut plane location of idealized tetrakaidecahedron (TKDH) structure. The model is developed based on assumptions of elastic deformations and TKDH structures which are applicable in the high porosity range of 0.85–0.95. An optimum value of porosity for minimizing the overall interface thermal resistance was determined with the model and experimentally validated.

Optimization of Hybrid Filler in Thermally Conductive Composite Formation

2017 ◽  
Vol 9 (4) ◽  
pp. 502-507
Author(s):  
Zhonglin Wei ◽  
Haibao Lu ◽  
Jianjun Li ◽  
Jihong Dong ◽  
Chuang Xue ◽  
...  
Keyword(s):  
Hybrid Filler ◽  
Conductive Composite ◽  
Composite Formation ◽  
Thermally Conductive

Thermally conductive composite films of hexagonal boron nitride and polyimide with affinity-enhanced interfaces

2010 ◽  
Vol 20 (14) ◽  
pp. 2749 ◽  
Author(s):  
Kimiyasu Sato ◽  
Hitomi Horibe ◽  
Takashi Shirai ◽  
Yuji Hotta ◽  
Hiromi Nakano ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Composite Films ◽  
Conductive Composite ◽  
Thermally Conductive
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