Functional module for acoustic/mechanical stimulation

Milestone M2 – Functional module for acoustic/mechanical stimulation describes the development and integration of a functional module for mechanical stimulation with a high-speed optical coherence tomography (OCT) system.

In summary:

• A piezoelectric transducer was designed to generate air-borne ultrasound at a frequency of 1.04 MHz, focused on the surface of a sample (for example, a cornea).

• The acoustic radiation force produced at the sample interface generates transient displacements, which in turn induce mechanical waves propagating through the sample.

• The transducer is driven by a waveform generator and an RF amplifier, and is positioned as close to perpendicular to the sample surface as experimentally feasible, so as not to block the OCT optical beam.

• Initial tests were conducted at AGH University in Cracow using a scattering gelatin phantom. Successive ultrasound pulses of 200 µs were delivered at 10 Hz, and a laser Doppler vibrometer was used to record microscopic displacements of the phantom surface induced by the ultrasound.

• The results demonstrated displacement maps of the phantom surface at different time instances (from 1 ms to 5 ms), confirming the propagation of elastic surface waves generated by non-contact ultrasound excitation.

Figure 1 (Figure1_M2) illustrates the experimental setup, showing the swept-source OCT instrument integrated with the mechanical stimulation module.
Figure 2 (Figure2_M2) presents the non-contact mechanical stimulation unit, highlighting the focusing air-coupled ultrasound transducer.
Figure 3 (Figure3_M2) displays the wave propagation maps of the gelatin phantom surface, recorded at successive time frames, which clearly demonstrate the dynamic motion induced by ultrasound excitation.

In conclusion, the non-contact mechanical stimulation module has been successfully developed, integrated with the OCT system, and experimentally validated, fulfilling the objectives of Milestone M2.