Masseladning

Masseladning refers to the addition of mass to a surface or device, typically through adsorption, deposition, or coating. The added mass modifies the system’s dynamic properties, most commonly its resonance characteristics. In mass-sensitive sensors, the amount of mass can be inferred from measurable changes in frequency, damping, or both.

In resonant devices such as quartz crystal microbalance (QCM) sensors, the relationship between added mass Δm and frequency change Δf is described by the Sauerbrey equation for rigid, thin films: Δf ≈ - (2 f0^2 Δm) / (A sqrt(ρq μq)). Here f0 is the fundamental frequency, A the active area, ρq the density of quartz, and μq its shear modulus. The equation shows that added mass lowers the resonance frequency in a predictable way. For non-rigid, viscoelastic layers, or thick adsorbates, the simple relation may not hold and dissipation measurements or more complex models are required.

Masseladning is used to characterize layer-by-layer adsorption, protein binding, thin-film deposition, and gas uptake on surfaces. It enables real-time monitoring of surface processes and can be calibrated to quantify mass per unit area. Practical measurement requires controlling temperature, surrounding medium viscosity, and other environmental factors, since they can influence frequency and damping.

Limitations include the assumption of a uniform, rigid film and the need to avoid large viscoelastic or porous layers where the Sauerbrey model fails. Overall, masseladning is a fundamental concept in surface science and sensor technology, describing how added mass alters dynamic behavior.