Nanoscale platinum printing on insulating substrates

Abstract

The deposition of noble metals on soft and/or flexible substrates is vital for several emerging applications including flexible electronics and the fabrication of soft bionic implants. In this paper, we describe a new strategy for the deposition of platinum electrodes on a range of materials, including insulators and flexible polymers. The strategy is enabled by two principle advances: (1) the introduction of a novel, low temperature strategy for reducing chloroplatinic acid to platinum using nitrogen plasma; (2) the development of a chloroplatinic acid based liquid ink formulation, utilizing ethylene glycol as both ink carrier and reducing agent, for versatile printing at nanoscale resolution using dip-pen nanolithography (DPN). The ink formulation has been printed and reduced upon Si, glass, ITO, Ge, PDMS, and Parylene C. The plasma treatment effects reduction of the precursor patterns in situ without subjecting the substrate to destructively high temperatures. Feature size is controlled via dwell time and degree of ink loading, and platinum features with 60 nm dimensions could be routinely achieved on Si. Reduction of the ink to platinum was confirmed by energy dispersive x-ray spectroscopy (EDS) elemental analysis and x-ray diffraction (XRD) measurements. Feature morphology was characterized by optical microscopy, SEM and AFM. The high electrochemical activity of individually printed Pt features was characterized using scanning electrochemical microscopy (SECM). Abstract. The deposition of noble metals on soft and/or flexible substrates is vital for several emerging applications including flexible electronics and the fabrication of soft bionic implants. In this article, we describe a new strategy for the deposition of platinum electrodes on a range of materials, including insulators and flexible polymers. The strategy is enabled by two principle advances: 1) the introduction of a novel, low-temperature strategy for reducing chloroplatinic acid to platinum using nitrogen plasma; 2) the development of a chloroplatinic acid based liquid ink formulation, utilising ethylene glycol as both ink carrier and reducing agent, for versatile printing at nanoscale resolution using dip-pen nanolithography (DPN). The ink formulation has been printed and reduced upon Si, glass, ITO, Ge, PDMS, and Parylene C. The plasma treatment effects reduction of the precursor patterns in situ without subjecting the substrate to destructively high temperatures. Feature size is controlled via dwell time and degree of ink loading, and platinum features with 60 nm dimensions could be routinely achieved on Si. Reduction of the ink to platinum was confirmed by Energy dispersive X-ray spectroscopy (EDS) elemental analysis and X-Ray Diffraction (XRD) measurements. Feature morphology was characterized by optical microscopy, SEM and AFM. The high electrochemical activity of individually printed Pt features was characterized using Scanning Electrochemical Microscopy (SECM).

Ink‐on‐Probe Hydrodynamics in Atomic Force Microscope Deposition of Liquid Inks

“…In dip‐pen nanolithography (DPN), an atomic force microscope (AFM) tip is used to deposit material onto a substrate with nano‐scale resolution and registry . Recently, the DPN technique has been applied to the deposition of liquid inks . (Note: The DPN moniker is technically used to describe the meniscus facilitated, or purely diffusive, transport of material from an AFM tip to substrate.…”

“…Recently, hydrogel inks loaded with proteins have been patterned for a novel drug‐delivery approach targeting single cells . Liquid inks are also seen as attractive due to their versatility in depositing on almost any material for the fabrication and repair of electronic devices …”

“…In contrast to molecular ink DPN, where ink depletion may constitute a minor adjustment to the prevailing model, the depletion of liquid inks causes a dramatic change in deposition rate. For example, it is accepted procedure to “bleed” a tip of excess liquid before “reproducible” dot sizes can be printed . Even after bleeding, the coefficient of variation in dot diameter is often quoted at between 10–15% .…”

Print‐Light‐Synthesis of Platinum Nanostructured Indium‐Tin‐Oxide Electrodes for Energy Research

“…[3b] Alternative fabrication routes for Pt/ITO particles and films are broad and include electrochemical deposition, [18] chemical reduction, [19] ultrahigh vacuum techniques, [20] thermal decomposition, [21] galvanostatic displacement of Cu, [22] and nitrogen plasma. [23] Furthermore, thin Pt layers on ITO glass are frequently used as catalytically active material on counter electrodes in dye-sensitized solar cells (DSSCs), in which Pt loadings below 3 µg cm −2 resulted in transparent catalyst films. [24] In addition, the ITO-coated glass slides are stable during the optimized photonic curing process.…”

Nano-bioelectronics via dip-pen nanolithography

“…Our group have since extended the electroless deposition approach to print nanoscale platinum features on sensitive substrates by using a mild plasma treatment to effect reduction of the printed precursor. 120 One of the first application-orientated DPN studies exploited patterned alkanethiols as etch resists to form gold and silicon nanostructures, highlighting the potential of DPN in the fabrication of nanoelectronics with <20 nm resolution and arbitrary pattern design. 83 This methodology has been successfully upscaled to polymer pen lithography.…”