Effect of pyrolysis process parameters on electrical, physical, chemical and electro-chemical properties of SU-8-derived carbon structures fabricated using the C-MEMS process

Pramanick, Bidhan; Vázquez-Piñón, Matías; Torres–Castro, Alejandro; Martínez-Chapa, Sergio O.; Madou, Marc

doi:10.1016/j.matpr.2017.10.153

Cited by 30 publications

(30 citation statements)

References 20 publications

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“…Other possible C-MEMS applications that benefit from the manufacturing of carbon nanowires with predictable feature sizes include label-free impedance-based nanobiosensors 55 , nanoparticle-based gas sensors 56 , and electrochemical immunosensors 5 . In these perspective applications, the multiple pyrolysis parameters (i.e., flow rate, heating/cooling ramp rate, intermediate/final temperatures, and dwell times) are expected to play a decisive role over the electrical, physical, and electrochemical properties of the derived glassy carbon 57 . However, in this introductory study, we decided to maintain the pyrolysis conditions fixed in order to focus on the impact of the prepyrolysis geometry on feature shrinkage.…”

Section: Discussionmentioning

confidence: 99%

Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model

et al. 2019

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The introduction of two-photon polymerization (TPP) into the area of Carbon Micro Electromechanical Systems (C-MEMS) has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography. Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy. In this work, we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900 °C. Through this process, photoresist microwires thermally decompose and shrink by as much as 75%, resulting in glassy carbon nanowires with linewidths between 300 and 550 nm. Even after the thermal decomposition induced by the pyrolysis step, the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters. We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires, but also in buckling in the case of slender carbon nanowires (for aspect ratios greater than 30). Furthermore, we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires, a trend that is consistent with several works found in the literature. This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures, serving as a simple guideline for shrinkage evaluation in other designs.

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Section: Discussionmentioning

confidence: 99%

Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model

et al. 2019

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“…This effect is attributed to an improved pyrolysis process, when the process is conducted in a saturated N 2 atmosphere. Regular furnace pyrolysis processes likewise require an inert atmosphere [ 2 , 25 , 31 ], and the quality of the pyrolytic carbon is typically affected by the presence of O 2 [ 25 , 41 ]. According to Ouyang and Hiraoka, oxidation may even cause etching (removal) of the carbon itself [ 41 ].…”

Section: Resultsmentioning

confidence: 99%

“…For carbon electrodes made by CMEMS and UV lithography, the desired electrode structure is defined by UV patterning of a photoresist followed by thermal treatment in a pyrolysis furnace [ 3 , 24 ]. There, it is heated to temperatures usually above 900 °C in an inert atmosphere for several hours to transform the photoresist into carbon through pyrolysis [ 24 , 25 ]. This approach usually provides excellent dimensional control and the possibility to tailor the electrode properties by the optimization of the pyrolysis process parameters [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

Selective Direct Laser Writing of Pyrolytic Carbon Microelectrodes in Absorber-Modified SU-8

et al. 2021

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Pyrolytic carbon microelectrodes (PCMEs) are a promising alternative to their conventional metallic counterparts for various applications. Thus, methods for the simple and inexpensive patterning of PCMEs are highly sought after. Here, we demonstrate the fabrication of PCMEs through the selective pyrolysis of SU-8 photoresist by irradiation with a low-power, 806 nm, continuous wave, semiconductor-diode laser. The SU-8 was modified by adding Pro-Jet 800NP (FujiFilm) in order to ensure absorbance in the 800 nm range. The SU-8 precursor with absorber was successfully converted into pyrolytic carbon upon laser irradiation, which was not possible without an absorber. We demonstrated that the local laser pyrolysis (LLP) process in an inert nitrogen atmosphere with higher laser power and lower scan speed resulted in higher electrical conductance. The maximum conductivity achieved for a laser-pyrolyzed line was 14.2 ± 3.3 S/cm, with a line width and thickness of 28.3 ± 2.9 µm and 6.0 ± 1.0 µm, respectively, while the narrowest conductive line was just 13.5 ± 0.4 µm wide and 4.9 ± 0.5 µm thick. The LLP process seemed to be self-limiting, as multiple repetitive laser scans did not alter the properties of the carbonized lines. The direct laser writing of adjacent lines with an insulating gap down to ≤5 µm was achieved. Finally, multiple lines were seamlessly joined and intersected, enabling the writing of more complex designs with branching electrodes and the porosity of the carbon lines could be controlled by the scan speed.

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“…It can be assumed from the change in the atomic percentage of oxygen (16.54%–4.93%) that most of the oxygen is removed from the MN structure, with only a small amount remaining. The identified oxygen present in the CMN arises from the contributions of the CMN structure and the Si/SiO 2 substrate surface 44 .…”

Section: Resultsmentioning

confidence: 99%

Glassy carbon microneedles—new transdermal drug delivery device derived from a scalable C-MEMS process

et al. 2018

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Because carbon is the basic element of all life forms and has been successfully applied as a material for medical applications, it is desirable to investigate carbon for drug delivery applications, as well. In this work, we report the fabrication of a hollow carbon microneedle array with flow channels using a conventional carbon-microelectromechanical system (C-MEMS) process. This process utilizes the scalable and irreversible step of pyrolysis, where prepatterned SU-8 microneedles (precursor) are converted to glassy carbon structures in an inert atmosphere at high temperature (900 °C) while retaining their original shape upon shrinkage. Once converted to glassy carbon, the microneedles inherit the unique properties of hardness, biocompatibility, and thermal and chemical resistance associated with this material. A comparative study of hardness and Young’s modulus for carbon microneedles and SU-8 microneedles was performed to evaluate the increased strength of the microneedles induced by the C-MEMS process steps. Structural shrinkage of the carbon microneedles upon pyrolysis was observed and estimated. Material characterizations including energy-dispersive X-ray spectroscopy (EDX) and Raman spectroscopy were carried out to estimate the atomic percentage of carbon in the microneedle structure and its crystalline nature, respectively. Our investigations confirm that the microneedles are glassy in nature. Compression and bending tests were also performed to determine the maximum forces that the carbon microneedles can withstand, and it was found that these forces were approximately two orders of magnitude higher than the resistive forces presented by skin. A microneedle array was inserted into mouse skin multiple times and was successfully removed without the breakage of any microneedles.

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Effect of pyrolysis process parameters on electrical, physical, chemical and electro-chemical properties of SU-8-derived carbon structures fabricated using the C-MEMS process

Cited by 30 publications

References 20 publications

Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model

Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model

Selective Direct Laser Writing of Pyrolytic Carbon Microelectrodes in Absorber-Modified SU-8

Glassy carbon microneedles—new transdermal drug delivery device derived from a scalable C-MEMS process

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