Fabrication of soft gold microelectrode arrays as probes for scanning electrochemical microscopy

Abstract

a b s t r a c tSoft linear gold microelectrode arrays for high throughput scanning electrochemical microscopy (SECM) imaging were fabricated using the Aerosol Jet Ò printing technology. Nanoparticulate gold ink was printed on polyimide Kapton HN Ò thin films. After sintering, a 200 nm thick Parylene C coating was deposited to cover and seal the gold tracks. A cross-section of the array of microelectrodes was exposed by laser cutting using an ArF excimer laser beam directed onto a metallic mask. Cyclic voltammograms, approach curves and SECM images in feedback mode demonstrate the capability of the arrays as SECM probes. Reactivity imaging of a platinum band structure on glass was performed with Parylene C coating facing the substrate providing an almost constant working distance. The softness of the array leads to a bending and allows scanning in contact mode like brushing the sample surface. For hard surfaces such as array electrode structures and similar materials, this occurs without detectable damage to the sample.

Parallel Imaging and Template‐Free Patterning of Self‐Assembled Monolayers with Soft Linear Microelectrode Arrays

“…[29] The pressure exerted by the probe on the sample is in the range of 10 3 N m À2 . [32] Although this value is not very precise because of difficulties in estimating the contact area between the probe and the substrate, it is around four orders of magnitude smaller than the pressure in standard SFM experiments. [33] Therefore, it should be possible to image delicate samples.…”

High-throughput scanning electrochemical microscopy brushing of strongly tilted and curved surfaces

“…Herein, the probe-sample contact is represented by the previously described quantity h P [49][50][51]53]. In short, if the probe is placed in solution bulk h P describes the vertical distance of the probe apex to the sample surface.…”

“…Recently, we have introduced soft carbon and gold microelectrode probes that are made in thin polymeric materials providing flexibility and mechanical stability to SECM imaging [49,50]. These probes are scanned in contact mode over surfaces in a brushinglike way achieving an almost constant d. This enables scanning of 3D patterns [51], slightly tilted [51] or even vertically orientated substrates [52] without additional instrumentation for distance control.…”

“…Even initially dry surfaces can be scanned if the mediator solution is provided and removed by means of microfluidics integrated into the probe [52]. Delicate surfaces such as self-assembled monolayers have been brushed without damaging them due to a very small mechanical pressure exerted by the probes on the surface [49,53]. Since the amperometric current response in SECM relies on the diffusional mass transport of the redox-active species with a time constant ≈ r T 2 ·D −1 , where r T is the radius of the UME and D is the diffusion coefficient of the redox species, probe translation rates faster than 25 m·s −1 have to be avoided in order to achieve an appropriate resolution and to exclude convectional disturbances [54].…”

“…industrial applications and quality testing). For this purpose, we have recently presented different soft linear arrays of microelectrodes as SECM probes [49,50,53,55]. Earlier approaches for SECM multi-tips were also reported, such as the two-dimensional imaging of O 2 , H 2 O 2 and glucose distributions by an array of 400 individually addressable Pt microelectrodes by Meyer et al [56], the linear independent 16 Pt microelectrode array from Barker et al [57] and the Au multinanotip electrode from Deiss et al [58]; however, in contrast to the soft probe arrays, the earlier developed approaches do not combine a constant working distance mode with individually addressable sensors for high-throughput reactivity imaging and surface modification.…”