VS-SDC Scanning Droplet Cell

• SDC controls a flowing droplet at the surface of the sample.  Users measure a subset of their sample using standard electrochemical methods
• Flowing the droplet ensures no impact of reaction products

The VersaSCAN Scanning Electrochemical Workstation is a single platform capable of providing spatial resolution to both electrochemical and materials-based measurements.  This system integrates a positioning system, measurement instrumentation and probe to provide local information.  Traditional electrochemical experiments measure an average response over the entire electrode, electrolyte interface.  Rarely is a sample homogenous.  Samples often consist of local sites of passivate or active nature and sites of anodic or cathodic character.  This need to investigate localized phenomenon led to the emergence of scanning probe electrochemistry.

Positioning System:

• VersaSCAN is unique in the use of piezoelectric motors to drive the stages on all axes.
• Piezos are materials that move with very high precision, accuracy, repeatability but over small distances.  We use them to drive stages; therefore we reach a combination of scan area and scan resolution that is unmatched.
• AFMs do not move with the same scan range (usually piezo-element only; without the stage)
• Alternative positioning system designs use step motors, exclusive or as a basis for a hybrid system, and cannot move with the same resolution.

System Installation and Training:

This is full ‘white-glove’ service. An experienced team member arrives on site – unpacked the instrumentation, assembles, levels the system.  A developed checkout procedure is executed on a test sample to verify the system (installation).  The fundamentals of the technique are covered.  The users are trained to execute the same test (training).

Multi-Technique platform:

The VersaSCAN platform offers the ability to leverage the positioning system and software as common components for other scanning probe techniques.  The best-in-class measurement characteristics of AMETEK equipment combines with this unique positioning system for high-resolution measurements even at large areas.

Scanning Droplet System (SDC) uses a compact peristaltic pump to force electrolyte through a small diameter tube and into a specifically designed head. This PTFE-based SDC head is machined to allow electrolyte to flow past an installed Reference Electrode and then to a port at the base of the head.

When the head is positioned sufficiently close to the sample a droplet forms between the head and sample. Tubing is also connected to an output port of the PTFE head. A second channel of the same peristaltic pump is then used to draw electrolyte past an installed Counter Electrode and out of the system.  SDC experiments can be configured to either:

• Apply a constant bias (potential, current or open (circuit) and increment position of the head creating a data map.
• Apply a static or dynamic electrochemical signal, such as a EIS experiment, a Tafel plot, or a Cyclic Voltammetry experiment as the head is kept in a fixed location.

Since electrochemistry occurs at an electrode/electrolyte interface, only the portion of the sample that is in contact with the droplet is being measured. This allows experiments to study a small area of a large sample, without cutting the sample and thus limiting edge effects.

When running, the SDC pump creates a flowing droplet. SDC’s pump velocity can be tuned to study different effects of flow rate.

• SDC technique confines the electrochemical measurement to the small droplet of electrolyte, defining the area of the electrode/electrolyte interface.
• Samples can be investigated without cutting the sample or subjecting areas to different electrolyte exposure times.
• Capable of running both constant bias/swept position plots for data maps and fixed-position/ dynamic signal plots for Cyclic Voltammetry, Tafel, EIS, etc.

 

 

VersaSCAN Positioning System

Specifications	VersaSCAN Base (VS-BASE)
Positioning System Range	X-axis:  100 mm Y-axis:  100 mm  Z-axis:  100 mm
Positioning Motor Technology	X-axis:  Piezoelectric motors,            no stepper-motor Y-axis:  Piezoelectric motors,            no stepper-motor Z-axis:  Piezoelectric motors,            no stepper-motor

SDC Measurement Technology

Specifications	VersaSTAT3
Max Current Output	±2 A (standard) up to ±20 A
Compliance Voltage	±12 V
EIS Capability	1 MHz, Option
Min Current Range	± 200 nA (6 pA resolution) down to ±4 pA (122 aA)
E and I Filters	200 kHz to 1 kHz,  including None
Grounding	Grounded, Earthed
SDC Head Material: PTFE
Tubing Material: Tygon
Reference Electrode: Ag/AgCl
Counter Electrode: Pt Wire