A method of evaluating viscoelastic properties of a fluid film as it interacts with a surface, the method comprising: applying a fluid under test to an oscillating surface of a mechanical resonator sensor, wherein the fluid comprises particles, which, after the fluid under test is applied to the oscillating surface, begin to couple to the oscillating surface to form a film that interacts with the oscillating surface; and detecting a change in resonant frequency Δ f and a change in half bandwidth ΔΓ of a resonance peak exhibited by the mechanical resonance sensor as the fluid under test forms the film that interacts with the oscillating surface; and evaluating two or more of: a first quantitative characteristic indicative of an effective mass M t̃ of the film interacting with the oscillating surface, a second quantitative characteristic indicative of an effective elasticity μ t̃ of the film interacting with the oscillating surface, and a qualitative characteristic indicative of a rigidity factor φ of an individual particle within the film interacting with the oscillating surface, wherein: M t ̃ = B Δf t z − Δ f t − ΔΓ t z 2 ΔΓ t + ΔΓ t z μ t ̃ = A ΔΓ t 2 ΔΓ t z 2 − ΔΓ t z 2 ΔΓ t 2 and φ = C μ t ̃ M t ̃ where A, B and C are coefficients of proportionality, Δ f ( t) and ΔΓ( t) are respectively the detected change in resonant frequency and half bandwidth of the resonant peak at a detection time t when the film has formed and is interacting with the oscillating surface, and Δf( t z) and ΔΓ( t z) are respectively the detected change in resonant frequency and half bandwidth of the resonant peak at a pre-interaction time t z which is after the fluid is applied but before any particles couple to the oscillating surface, where t z < t. applying a fluid under test to an oscillating surface of a mechanical resonator sensor, wherein the fluid comprises particles, which, after the fluid under test is applied to the oscillating surface, begin to couple to the oscillating surface to form a film that interacts with the oscillating surface; and detecting a change in resonant frequency Δ f and a change in half bandwidth ΔΓ of a resonance peak exhibited by the mechanical resonance sensor as the fluid under test forms the film that interacts with the oscillating surface; and evaluating two or more of: a first quantitative characteristic indicative of an effective mass M t̃ of the film interacting with the oscillating surface, a second quantitative characteristic indicative of an effective elasticity μ t̃ of the film interacting with the oscillating surface, and a qualitative characteristic indicative of a rigidity factor φ of an individual particle within the film interacting with the oscillating surface, wherein: M t ̃ = B Δf t z − Δ f t − ΔΓ t z 2 ΔΓ t + ΔΓ t z μ t ̃ = A ΔΓ t 2 ΔΓ t z 2 − ΔΓ t z 2 ΔΓ t 2 and φ = C μ t ̃ M t ̃ where A, B and C are coefficients of proportionality, Δ f ( t) and ΔΓ( t) are respectively the detected change in resonant frequency and half bandwidth of the resonant peak at a detection time t when the film has formed and is interacting with the oscillating surface, and Δf( t z) and ΔΓ( t z) are respectively the detected change in resonant frequency and half bandwidth of the resonant peak at a pre-interaction time t z which is after the fluid is applied but before any particles couple to the oscillating surface, where t z < t. a first quantitative characteristic indicative of an effective mass M t̃ of the film interacting with the oscillating surface, a second quantitative characteristic indicative of an effective elasticity μ t̃ of the film interacting with the oscillating surface, and a qualitative characteristic indicative of a rigidity factor φ of an individual particle within the film interacting with the oscillating surface, wherein: M t ̃ = B Δf t z − Δ f t − ΔΓ t z 2 ΔΓ t + ΔΓ t z μ t ̃ = A ΔΓ t 2 ΔΓ t z 2 − ΔΓ t z 2 ΔΓ t 2 and φ = C μ t ̃ M t ̃ where A, B and C are coefficients of proportionality, Δ f ( t) and ΔΓ( t) are respectively the detected change in resonant frequency and half bandwidth of the resonant peak at a detection time t when the film has formed and is interacting with the oscillating surface, and Δf( t z) and ΔΓ( t z) are respectively the detected change in resonant frequency and half bandwidth of the resonant peak at a pre-interaction time t z which is after the fluid is applied but before any particles couple to the oscillating surface, where t z < t.