In-situ

In-situ measurements are those where the sample-of-interest is studied in a scientifically-relevant environment (as opposed to an artificial environment convenient for the instrument; e.g. vacuum). Thus, proteins studied in their native liquid environment, or polymer films studied during thermal processing, are examples of in-situ.

Because x-rays and neutrons are strongly penetrating, scattering experiments are well-suited to being performed in-situ (this is one of the key advantages of scattering). Thus, materials can be probed under realistic 'native' conditions, or during relevant processing/transformation conditions. One can also define in-operando, wherein materials are studied during operation (e.g. a battery studied during charging/discharging). More abstractly, one can consider in-situ the study of materials under prescribed equilibrium conditions, whereas in-operando is the study during prescribed non-equilibrium (e.g. time-varying) conditions.

Examples

• Environment
  • Solvent
    • Water
      • Control ionic strength, pH, concentration, etc.
  • Vapor
    • Humidity
    • Solvent exposure (solvent annealing)
• Thermal
  • Heating/annealing
  • Cooling
  • Thermal cycling
  • Thermal gradients
• Mechanical force
  • Pressure (c.f. diamond anvil cell)
  • Stretching
  • Shear
• Applied fields
  • Electric
  • Magnetic
• Irradiation
  • Visible light, IR, UV, etc.

Literature

• Vanessa K. Peterson and Christine M. Papadakis Functional materials analysis using in situ and in operando X-ray and neutron scattering IUCrJ 2015, 2 (2). doi: 10.1107/S2052252514026062