Difference between revisions of "Fabrication of Bio-Inspired Actuated Nanostructures with Arbitrary Geometry and Stiffness"

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Wiki entry by :  Dongwoo Lee, AP225 Fall 2010.
 
Wiki entry by :  Dongwoo Lee, AP225 Fall 2010.
  
Paper in this Wiki : Adam C. Siegel, Scott T. Phillips, Michael Dickey, Nanshu Lu, Zhigang Suo, George M. Whitesides, Foldable printed circuit boards on paper substrates. Advanced Functional Materials 20, 28-35 (2010).
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Paper in this Wiki : Fabrication of Bio-Inspired Actuated Nanostructures with Arbitrary Geometry and Stiffness, B. Pokroy, A. K. Epstein, M. C. M. Persson-Gulda, J. Aizenberg, Adv. Mater., 2009, 21, 463-469.
  
  
 
== Summary ==
 
== Summary ==
  
[[Image:dongwoo8.png|500px|right|thumbnail|Fig. 1.General scheme for fabricating flexible electronic circuits on fiber-based substrates. Fig. 2. The ratio of measured conductivity (Gmeas) to initial conductivity (G0) of an evaporated tin wire on a glossy photo paper versus folding iteration. Fig. 3. Properties of paper-based electronic circuits. a,b) Trimming and burning fiber-based electronic circuits. c) Topologically complex electronic circuits on paper demonstrating the ability to form foldable electronic circuits]]
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[[Image:dongwoo8.png|500px|right|thumbnail|     ]]
  
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The paper describes the fabrication method of high aspect ratio pillar structure which is inspired by biology. (This structure is utilized by creatures such as Gecko lizard to create sticking force between vertical surface and his foot pad.) The main advantage of this method is that it can produce low cost pillar structure with variety materials and orientations. In this work, PDMS was used as a mold not as the final structure. Fig. 1. shows the fabrication procedure. Si nanoposts were fabricated first then PDMS was poured on it. Now, one can change the orientation (Fig.2) of the holes in the PDMS mold to cast the final structure with desired orientation and material. (With various materials, the authors could create the pillar structures with a stiffness that ranges from 1MPa to several gigaPascals.) The authors investigated the actuation ability of the structure. (fig. 3) The actuation is driven by the electrostatic forces imposed by the e-beam. The movement is reversible and can be repeated multiple times.
  
The authors illustrate the fabrication methods and properties of the paper based flexible electronic circuits. The advantage of this research is that one can create the low-cost, multi-functional, 3D-structured circuits with the everyday product, paper. Fig 1. shows the schematic of the fabrication process for the printed circuit. A laser cutted stencil makes patterned conductive paths to connect electronic components since metal is deposited on the designated region. Then, conductive epoxy was used to make connections between the components and the metal lines. Even though the fabrication method is quite simple, circuits created showed good enough performances in terms of flexibility as shown in the fig. 2. By using the general concept, the authors showed several possible applications, such as circuit on origami paper with 3D shape. (fig 3)
 
  
 
==Soft Matter Discussion==
 
==Soft Matter Discussion==
 
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The paper talks about a creative and simple method to fabricate bio-inspired pillar structure. Compared to the previous works, this work made it possible to fabricate multi-matarial and multi-oriented pillar structure that more resembles to the counterparts in real world. One can improve the functionality of the structure introducing hierarchical structures. In real Gecko lizard's foot pad, there are multi scale structure to make it stick to the wall as close as possible. Also, more kind of materials can be casted in the PDMS mold once the knowledge about material compatibility is clear. Last, to make the structure have the sensing ability as fish can sense the flow with its micro pillars on its skin, optics knowledge can be utilized. In robotics. This concept was implemeted in a robotics paper. [1]
It is beneficial to integrate soft and hard material since the the composite can be used for developing the cutting-edge devices such as wearable electronics and flexible display. The paper introduces a cheap method to fabricate the paper based electronics and its characteristics. The main advantage of this method is that the process is very low cost compared to the polymer based electronics for the flexible circuits. One problem of this method is the fatigue property. As can be seen in the fig. 2, the standard deviation is large, meaning that the device is not reliable to use. One may be able to solve this problem introducing more flexible electrically conductive material in the folding area. For example, one can make conductive liquid be trapped in the edge lines(folding lines) so that the conductivity is remained for several number of folds. One of the limitation of this method is in scaling. In the work, they chose the conductive material as Tin, zinc, silver and indium which are ductile. However, it was found that ductile material becomes brittle when its thickness is approximately a few nano-meters. Also, smoother papers should be used for the small paper based electronics since the roughness of the paper effects on the conductivity, as described in the paper. Even though there are some future works to be done for real application of this method, the general idea of this paper is simple and quite creative and is expected to be used in everyday products soon.
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Revision as of 04:54, 2 November 2010

Information

Wiki entry by : Dongwoo Lee, AP225 Fall 2010.

Paper in this Wiki : Fabrication of Bio-Inspired Actuated Nanostructures with Arbitrary Geometry and Stiffness, B. Pokroy, A. K. Epstein, M. C. M. Persson-Gulda, J. Aizenberg, Adv. Mater., 2009, 21, 463-469.


Summary

Dongwoo8.png

The paper describes the fabrication method of high aspect ratio pillar structure which is inspired by biology. (This structure is utilized by creatures such as Gecko lizard to create sticking force between vertical surface and his foot pad.) The main advantage of this method is that it can produce low cost pillar structure with variety materials and orientations. In this work, PDMS was used as a mold not as the final structure. Fig. 1. shows the fabrication procedure. Si nanoposts were fabricated first then PDMS was poured on it. Now, one can change the orientation (Fig.2) of the holes in the PDMS mold to cast the final structure with desired orientation and material. (With various materials, the authors could create the pillar structures with a stiffness that ranges from 1MPa to several gigaPascals.) The authors investigated the actuation ability of the structure. (fig. 3) The actuation is driven by the electrostatic forces imposed by the e-beam. The movement is reversible and can be repeated multiple times.


Soft Matter Discussion

The paper talks about a creative and simple method to fabricate bio-inspired pillar structure. Compared to the previous works, this work made it possible to fabricate multi-matarial and multi-oriented pillar structure that more resembles to the counterparts in real world. One can improve the functionality of the structure introducing hierarchical structures. In real Gecko lizard's foot pad, there are multi scale structure to make it stick to the wall as close as possible. Also, more kind of materials can be casted in the PDMS mold once the knowledge about material compatibility is clear. Last, to make the structure have the sensing ability as fish can sense the flow with its micro pillars on its skin, optics knowledge can be utilized. In robotics. This concept was implemeted in a robotics paper. [1]