Projects

@article{Ruppert2025,

title = {Modulated-Illumination Intermittent-Contact Tip-Enhanced Raman Spectroscopy},

author = {M. G. Ruppert and B. S. Routley and L. R. McCourt and Y. K. Yong and A. J. Fleming},

doi = {https://doi.org/10.1021/acs.nanolett.4c06397},

year  = {2025},

date = {2025-03-13},

urldate = {2025-03-13},

journal = {ACS Nano Letters},

abstract = {This article presents a proof-of-concept for a new imaging method that combines tip-enhanced Raman spectroscopy with intermittent-contact atomic force microscopy to provide simultaneous nanometer-scale mechanical imaging with chemical contrast. The foremost difference from a standard tip-enhanced Raman microscope is the Raman illumination, which is modulated by the cantilever drive signal so that illumination is only active when the tip is close to the surface. This approach significantly reduces contact forces and thermal damage due to constant illumination while simultaneously reducing background Raman signals. Near-field optical and dynamic cantilever simulations highlight the effect of the imaging parameters on the tip–sample force and the evanescent field enhancement. The experimental images obtained with this new imaging method demonstrate a lateral resolution sufficient to identify single-walled carbon nanotube bundles with a full width at half-maximum of 20 nm.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J23a,

title = {Feasibility of gold nanocones for collocated tip-enhanced Raman spectroscopy and atomic force microscope imaging },

author = {L. R. McCourt and B. S. Routley and M. G. Ruppert and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2024/02/J23a-Preprint.pdf},

doi = {10.1002/jrs.6625},

issn = {1097-4555},

year  = {2024},

date = {2024-02-01},

urldate = {2024-02-01},

journal = {Journal of Raman Spectroscopy},

abstract = {Microcantilever probes for tip-enhanced Raman spectroscopy (TERS) have a grainy metal coating that may exhibit multiple plasmon hotspots near the tip apex, which may compromise spatial resolution and introduce imaging artefacts. It is also possible that the optical hotspot may not occur at the mechanical apex, which introduces an offset between TERS and atomic force microscope maps. In this article, a gold nanocone TERS probe is designed and fabricated for 638 nm excitation. The imaging performance is compared to grainy probes by analysing high-resolution TERS cross-sections of single-walled carbon nanotubes. Compared to the tested conventional TERS probes, the nanocone probe exhibited a narrow spot diameter, comparable optical contrast, artefact-free images, and collocation of TERS and atomic force microscope topographic maps. The spot diameter was 12.5 nm and 19 nm with 638 nm and 785 nm excitation, respectively. These results were acquired using a single gold nanocone probe to experimentally confirm feasibility. Future work will include automating the fabrication process and statistical analysis of many probes.},

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{J24b,

title = {Thermal Protection of Piezoelectric Actuators Using Complex Electrical Power Measurements and Simplified Thermal Models},

author = {Y. K. Yong and A. A. Eielsen and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2024/02/J24b-preprint.pdf},

doi = {10.1109/TMECH.2023.3277437},

isbn = {1083-4435},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {IEEE/ASME Transactions on Mechatronics},

abstract = {This article describes a method for estimating the temperature of high-power piezoelectric actuators when a direct temperature measurement is impractical. The heat flow is estimated from the real component of the electrical power; then, the temperature is estimated by a transfer function that approximates the thermal response of the system. The transfer function can be derived analytically from a lumped-element approximation or calibrated experimentally by using a system identification method. The proposed method is demonstrated on a piezoelectric stack actuator used in a high-speed nanopositioning device. A second-order transfer function estimates the temperature to within 3  ∘ C of a reference measurement for a range of operating conditions. The proposed method is suitable for protecting piezoelectric actuators in applications where direct temperature measurement is impractical, for example, due to space or wiring constraints.},

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{J23a,

title = {Modeling of soft fluidic actuators using fluid-structure interaction simulations with underwater applications},

author = {M. S. Xavier and S. Harrison and D. Howard and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2023/06/FSI.pdf},

doi = {10.1016/j.ijmecsci.2023.108437},

issn = {1879-2162},

year  = {2023},

date = {2023-05-15},

urldate = {2023-05-15},

journal = {International Journal of Mechanical Sciences},

volume = {255},

issue = {108437},

pages = {1-11},

abstract = {Soft robots have been developed for a variety of applications including gripping, locomotion, wearables and medical devices. For the majority of soft robots, actuation is performed using pneumatics or hydraulics. Many previous works have addressed the modeling of these fluid-driven soft robots using static finite element simulations where the pressure inside the actuator is assumed to be constant and uniform. The assumption of constant internal pressure is a useful simplification but introduces significant errors during events such as pressurization, depressurization, and transient loads from a liquid environment. Applications that use soft actuators for locomotion or propulsion operate using a sequence of transient events, so accurate simulation of these events is critical to optimizing performance. To improve the simulation of soft fluidic actuators and enable the modeling of both internal and external fluid flow in underwater applications, this work describes a fully-coupled, three-dimensional fluid–structure interaction simulation approach, where the pressure and flow dynamics are explicitly solved. This approach provides a realistic simulation of soft actuators in fluid environments, and permits the optimization of transient responses, which may be due to a combination of environmental fluid loads and non-uniform pressurization. The proposed methods are demonstrated in a number of case studies and experiments for a range of actuation and both internal and external inlet flow configurations, including bending actuators, a soft robotic fish fin for propulsion, and experimental results of a bending actuator in a high-speed fluid, which correlate closely with simulations. The proposed approach is expected to assist in the design, modeling, and optimization of bioinspired soft robots in underwater applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}