From Displacement to Angle: Diamond-Based 3D Rotation Sensing for High-Precision Cellular Force Measurement

Area of Science:

• Mechanobiology
• Biophysics
• Materials Science

Background:

• Cellular traction forces are crucial for cell migration and tissue development.
• Conventional methods track bead/micropillar displacement, which can be inaccurate for large deformations.
• Existing techniques often overlook 3D pillar movements and can introduce geometric-nonlinearity errors.

Purpose of the Study:

• To introduce a novel method for quantifying cellular forces using pillar rotation.
• To enhance the precision and scope of force measurements in mechanobiology.
• To overcome limitations of displacement-based force sensing techniques.

Main Methods:

• Utilized fluorescent nanodiamonds (FNDs) as 3D orientation markers embedded in polydimethylsiloxane (PDMS) micropillars.
• Integrated optically detected magnetic resonance (ODMR) with laser polarization modulation (LPM) for precise FND orientation determination (∼0.5°).
• Developed an angle-based measurement framework for force reconstruction from pillar rotation.

Main Results:

• Demonstrated sub-degree precision in determining FND 3D orientation within micropillars.
• Showcased robust force reconstruction for stocky beams and large deformations via pillar rotation.
• Finite-element simulations confirmed >10% reduction in force estimation errors compared to displacement methods.
• Successfully captured 3D pillar deformations (bending, in-plane rotation) previously inaccessible.

Conclusions:

• Established diamond-based angular force microscopy as a high-precision platform for mechanobiology.
• The new method provides a more accurate and comprehensive analysis of cellular forces.
• This technique opens new avenues for studying cell-environment interactions.