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Institute of Robotics and Intelligent Systems Department of Mechanical and Process Engineering (DMAVT) ETH Zurich
Exercise Session 4 NANOROBOTICS 2015 Assistants: Marcus Hoop ([email protected])
Berna Özkale ([email protected]) Dr. Salvador Pané Prof. Dr. Bradley J. Nelson
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Paper 1
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Paper 1
Nature Materials 6, 429 – 433, 2007
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Question 1
• Additionally a graph showing the influence of solvent polarity on swelling ratio is reported in the same paper (Figure 1). If the reported hydrogel were meant to be used for cleaning VOCs, discuss how effective it would be if the spillage mainly contains THF (ε = 7.6) or acetonitrile (ε = 36). Would you use type 1 or type 2? Explain your answer.
Type I
Type II
Q ≈ 5
Q ≈ 25
Q ≈ 125 § Type I § THF collection
would be more effectively achieved since the hydrogel can absorb 25x more THF compared to acetonitrile.
Swelling ratio: Q = (Wwet −Wdry )Wdry Nature Materials 6, 429 – 433, 2007
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Question 1
• Nanorobots made of type I hydrogel are used to clean up a small scale spillage involving tetrahydrofuran (THF) as a proof of concept. The nanorobots have the shape of a perfect solid sphere. Assuming that the swelling ratio stays the same, determine the number of hydrogel nanorobots necessary to clean 1 l of THF. The diameter of the sphere is 2 µm.
v2,s =VpVg
=Q−1
VpVg
=125−1
Vp =43πr3
Vp = 4.2µm3
Vg = 525µm3
Vg,t =1015 µm3
525µm3=1.9×1012nanorobots
1 l = 1000 ml = 1000 cm3 = 1015 µm3
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Question 2
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Question 2
• Write the oxidation and reduction reactions involved. • Explain the working principle of the described hydrogel. How does the hydrogel change
its shape, on which component is this mechanism dependent on?
Cu+ Cu2+ + 1e-
reduction
oxidation
ACS Macro Letters 2, 1095 – 1099, 2013
§ Chemical stimulus: oxidation in air and recovery by sodium metabisulfite
§ Electrochemical stimulus: negative potential