Gemini HR nano performance - the proof

• The Bohlin Gemini rheometer possesses advanced and powerful technical specifications enabling a complete range of rheological properties to be assessed.
• Continued development of renowned state of the art air bearing design, coupled with the enhanced and patented Rotonetic 2 drive system, has allowed expansion of the Gemini series to include the Gemini HR nano.
• This flagship instrument realises unsurpassed range and sensitivity to control torque and speed across all steady, dynamic and transient test modes.
• Measurement and control down to nNm torque levels opens up new opportunities for probing weak or sensitive material structures.

Intrinsic instrument performance is shown in the examples below:

Low torque performance in stress control and rate control modes

1.0Pas Newtonian reference Oil (stress control mode illustrated):

The inherent torque map function used in the Gemini Rheometer ensures that the air bearing response is linear down to minimum torque in BOTH controlled stress and controlled rate operating modes.
Using the same Newtonian 1.0Pas reference oil in controlled rate mode, data with a SD of <5% is realisable down to a minimum torque of 10nNm.

Why is low torque performance important in these operating modes?
Provides more reliable and reproducible data when determining yield stress, creep retardation responses, and the linear viscoelastic region (in oscillation). Provides more reliable and reproducible data when determining the zero shear viscosity at low shear rates, and the low frequency oscillation spectrum.

Stability performance at low torque settings

1.0Pas reference Oil, viscosity data reported at 10nNm applied torque with time:

Why is time stability performance at very low applied torques important?
Constant stress (torque) measurements in steady shear or dynamic mode are particularly useful for determining rebuild properties of thixotropic materials – invariably the rebuild process occurs at ‘rest conditions’ so the response data at low stress can be very critical.

Oscillation – Applied torque performance (stress sweep)

1.0Pas Newtonian reference Oil

Why is dynamic applied torque performance (stress control) important?
Reliable response at low stress in oscillation provides an important insight into product stability, especially when trying to determine shelf life and degree of flocculation.

Oscillation – Measured torque performance (strain sweep)

1.0Pas Newtonian reference Oil

Why is dynamic measured torque performance (strain control) important?
Low strains on weakly structured and low viscosity systems command low torque signals. Reliable data in this region is important for determining the ‘critical strain’ which is a key component in understanding applications like shelf life, and stability.