General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.

Users may download and print one copy of any publication from the public portal for the purpose of private study or research.

You may not further distribute the material or use it for any profit-making activity or commercial gain

You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Downloaded from orbit.dtu.dk on: Aug 27, 2020

Microfabrication of multi-layered 3D pyrolysed carbon electrodes

Hemanth, Suhith; Caviglia, Claudia; Amato, Letizia; Keller, Stephan Sylvest

Publication date:2015

Document VersionPublisher's PDF, also known as Version of record

Link back to DTU Orbit

Citation (APA):Hemanth, S., Caviglia, C., Amato, L., & Keller, S. S. (2015). Microfabrication of multi-layered 3D pyrolysedcarbon electrodes. Poster session presented at 41st International conference on Micro and Nano Engineering ,The Hague, Netherlands.

IntroductionFabrication, characterisation and testing of a highly efficient and simple electrochemical cell/batch system, with pyrolysed carbon (Carbon4Bio) as workingelectrode is presented. A unique microfabrication technique for 3D carbon microelectrode is also presented.

Presenting authorSuhith HemanthPh.D. Studentsuhem@nanotech.dtu.dk

Authors affiliationBiomaterial MicrosystemsStephan Sylvest KellerStephan.Keller@nanotech.dtu.dk

References

[1] Letizia Amato, Pyrolysed carbon scaffolds for bioelectrochemistry in lifescience,PhD thesis, December 2013.[2] Wang, C., Taherabadi, L. H. & Madou, M. J. A novel method for the fabrication ofhigh-aspect ratio C-MEMS structures. Journal of Microelectromechanical Systems14, 348–358 (2005).

Microfabrication of multi-layered 3D pyrolysed carbon electrodes

Suhith Hemanth, Claudia Caviglia, Letizia Amato, Stephan Sylvest Keller Biomaterial Microsystems, DTU Nanotech, DK 2800 Kongens Lyngby

Fabrication of 2D Carbon4Bio chips An three electrode electrochemical cell (Carbon4Bio) wasfabricated, with pyrolysed carbon as working and counterelectrodes and Au as pseudo-reference electrodes.

Carbon lead width characterisation

Conclusion and Outlook • As the width and thickness of pyrolysed carbon increases, the overall resistance decreases and the increases the sensitivity of the C4B chips.• Microfabrication process flow for 3D microcarbon is established with UV photolithography.• Fabrication of electrochemical cell with 3D carbon as the working electrode.

Figure 1: Scematic of prolysis process with multi-step carbonizationprocess taking place during pyrolysis for life science application [1] [2].

Figure 4: Top view of C4B chips: (a)schematic (b) optical microscopyimages showing WE (Carbon), RE,passivation layer (SU-8).

(b)

Figure 6: : CV using 10M ferri-ferrocyanide asredox probe shows that as the width of thecontact lead increases the ΔEp decreases andthe Ip increases. Thickness of carbon electrodeis 624nm .

Carbon thickness characterisation

900 °C, N2

Polymer Pyrolysis

Carbon

Figure 5: Magnitude of impedance and phase angleof carbon electrode (lead width – 700µm) withdifferent thickness in PBS. As the thickness of carbonincreases, the overall resistance decreases.

Acknowledgments

This work was financially supported by DTU Nanotechand The Velux Foundations.

20µm

Figure 2:MagClamp systemsfor electrochemical analysisin batch system.

(a)

30m

m

10mm

C

Figure 3: Process flow for Carbon4Bio(C4B)chips (a) photolithography pattering (b)pyrolysis and pseudo reference electrode (RE)in Au defined via ebeam evaporation througha shadow mask .

(a)

(b)(b)

Fabrication of 3D microelectrodes 3D SU-8 process optimization

3D carbon microelectodes

Figure 7: Process flow for 3D multi-layered microelectrode (a)complete UV exposure (147 mJ cm-2 ) (b) partial UV exposure (28 mJcm-2 ) (c) Development in PGMEA (d) Pyrolysis at 900 ºC for 1h (e)repeating steps a and b sequencally results in 3D structures

(a)

(b)

(c)

(d)

(e)

Figure 8: Optimization of partial UVphotolithography with difference exposuredose: (a) 21 mJ cm-2 ; (b) 28 mJ cm-2 ; (c) 35mJ cm-2 ; (d) 42 mJ cm-2 (Scale bar – 20µm) .

PyrolysisSU-8 Carbon

Figure 9: (a) SU-8 template and carbon microstructures; (b) smallest feature sizeof 4µm (c) two layer carbon microstructures (Scale bar – 20µm) .

(a)

B C

00.40.81.21.6

2

500700 250

ΔEp

0

0.0001

0.0002

0.0003

700 500 250

Ip