Carbon MEMS

Fabrication of carbon structure through pyrolysis of photoresist structure

: Dramatic size reduction up to ~90 %, highly inert carbon electrode with fancy structure.

1. Electrochemical sensor platform

1:1 aspect ratio IDA nanoelectrodes

Batch fabrication of interdigitated nanoelectrode array.

• Gap between electrode reduced down to 1.65 μm
• 1:1 aspect ratio (height: 340 nm, width: 300 nm)
• Redox cycling: High electrochemical signal amplification

J. -I. Heo, D. S. Shim, G. Turon Teixidor, S. Oh, M. J. Madou, H. Shin, , "Carbon Interdigitated Array Nanoelectrodes for Electrochemical Applications," Journal of Electrochemcial Society 158, J76 (2011).

http://jes.ecsdl.org/content/158/3/J76/F3.expansion.html

Effect of microchannel

Effect of microchannel height on redox cycling effect of integrated interdigitated carbon nanoelectrode array.

• PDMS channel integration
• Current amplification up to 1116 times.

J. -I. Heo, Y. Lim, H. Shin, "Effect of channel height and electrode aspect ratio on redox cycling at carbon interdigitated array nanoelectrodes confined in a microchannel," Analyst 138, 6404 (2013).

http://pubs.rsc.org/is/content/articlehtml/2013/an/c3an00905j

Stacked electrode set

Stacked carbon electrode set including a suspended mesh made of nanowires and a substrate-bound planar electrode.

• Electrode gap reduced down to 2.1 μm
• Unit mesh size: 300–320-nm-wide and 560–600-nm-thick
• Redox current amplification(Ferrocyanide): 37 times
• Dopamine detection down to 5 μM

Y. Lim, J. I. Heo, H. Shin, “Fabrication and application of a stacked carbon electrode set including a suspended mesh made of nanowires and a substrate-bound planar electrode toward for an electrochemical/biosensor platform,” Sensors and Actuators B 192, 796 (2014)

http://www.sciencedirect.com/science/article/pii/S0925400513014159

2. Biosensors

Glucose sensor

Selective immobilization of enzyme for glucose sensor application. One of the IDA was selectively modified with GOx via the electrochemical reduction of an aryl diazonium salt, while the other comb remained unmodified. Increased active electrode surface resulted in better performance.

• Electrode gap between two combs: 1.9 μm
• Sensitivity enhancement: ~2.3 times
• LOD enhancement: ~295 times

D. Sharma, Y. Lim, Y. Lee, H. Shin* , Glucose sensor based on redox-cycling between selectively modified and unmodified combs of carbon interdigitated array nanoelectrodes, Analytica Chimica Acta, in print.

http://ac.els-cdn.com/S0003267015009095/1-s2.0-S0003267015009095-main.pdf?_tid=86b4879a-bc44-11e6-8f66-00000aacb361&acdnat=1481091498_d5668c368bc9fd1facb5853f12f759be

Biosensor platform: AuNP/C IDA nanoelectrodes

Fabrication of an electrochemical-enzymatic redox cycling-based cholesterol biosensor using 1:1 carbon interdigitated array (IDA) nanoelectrodes decorated selectively with electrochemically deposited gold nanoparticles (AuNPs).

• Nanoparticle size: 50~70 nm
• Sensitivity enhancement: 20~30 %
• LOD enhancement: 2~3 times

In review

3. Gas sensors

Suspended single carbon nanowire as sensor platform

• Full utilization of high surface to volume ratio
• Improved mass transport
  • No interference from the substrate

Y. Lim, J. I. Heo, M. J. Madou, H. Shin, “Monolithic carbon structures including suspended single nanowires and nanomeshes,” Nanoscale Research Letters 8, 492 (2013).

http://link.springer.com/article/10.1186/1556-276X-8-492

Suspended single carbon nanowire functinalized with Pd thin film

• High hydrogen selectivity
• High sensitivity related to Pd material property
• Room temperature operation

Y. Lim, Y. Lee, J. I. Heo, H. Shin, “Highly sensitive hydrogen gas sensor based on a suspended palladium/carbon nanowire fabricated via batch microfabrication,” Sensors and Actuators B, 210, 218, (2015).

http://www.sciencedirect.com/science/article/pii/S0925400514016554

An array of suspended carbon nanowires functionalized Pd nanoparticles

• Controllable Pd nanoparticle morphology
• Wide sensing range according to array structure of nanowires
• High sensing performance according to self-heating effect
• Room temperature operation

In review

Multiplex gas sensor: Suspended MOx NWs

ZnO nanowires were grown selectively on a suspended single glassy carbon nanowire using hydrothermal method so that the detrimental effects from the substrate inclusive of contamination, stagnant layer and limited mass transfer could be alleviated.

• ZnO nanowire diameter: 30~80 nm
• ZnO nanowire length: 0.5~2 μm

In preparation

Nanoporous carbon

Carbonization of plasma etched polymer precursor

Patternable and controllable multiscale porous 3D carbon structures

• Large surface area & Electric conductivity : Supercapacitors, Sensors, etc.
• Polymer based batch process : Cost-effective

4. Material process

RTA-induced conductivity enhancement

Enhancing the electrical conductivity of GC, so that it can compensate or be substituted for other carbon allotropes such as graphite, carbon nanotubes, and graphene. After the RTA process, the carbon/oxygen content and G-/D-band intensity ratios, which are correlated to the electrical conductivity, were enhanced, depending on the pyrolysis temperature.

• More ordered carbon phase via RTA
• Electrical conductivity enhancement: 3.3 times

In review

5. Micro- and Nano mixed-scale channel networks

• Channel replication using a monolithic mixed-scale carbon mold

PDMS channel networks

• Simple fabrication of mixed-scale polyldimethylsiloxane (PDMS) channel networks via single molding process
  • High throughput channel molding process
  • Efficient single particle entrapment in Kingfisher-beak-shaped 3D microfunnel

Y. Lee, Y. Lim, H. Shin*, Mixed-scale channel networks including Kingfisher-beak-shaped 3D microfunnels for efficient single particle entrapment, Nanoscale 8 (2016) 11810-11817 (Front cover).

http://pubs.rsc.org/is/content/articlehtml/2016/nr/c6nr00114a

PMMA channel networks

• Simple fabrication of mixed-scale polymethyl methacrylate(PMMA) channel networks via thermal nanoimprint method
  • Repeated nanoimprint process owing to mechanically and chemically superb carbon mold.
  • Smooth single particle entrapment via diffusiophoresis

SECM-AFM

Combination of atomic force microscopy(AFM) and scanning electrochemical microscopy(SECM)

: Simultaneous scanning of topography and electrochemical data of sample surface

Multifunctional Probe

Combined atomic force–scanning electrochemical microscopy

Scanning probe microscopes integrated with dual or single micro/nano electrode

• Simultaneous multiple surface data collection: topology, electrochemical data, pH, biological data, temperature, etc.
• Collection of biological data inside live cells

Conductive Material Nano-Printing

Localized electrochemical deposition of conductive materials using AFM probes

• AFM cantilever tip integrated with micro/nano electrode
• Continuous conductive material printing with high resolution