Focal laser ablation is a minimally
invasive treatment for prostate cancer. This treatment requires the positioning
of an optical fibre with the use of a needle, to then thermally and locally
destroy cancer cells utilising this optical fibre. Traditional needles
experience buckling, which results in less accurate treatment and tissue
damage. The ovipositor of the parasitic wasp offers a solution, which already
resulted in the development of ovipositor-inspired needles. In this study a
friction-based ovipositor-inspired needle actuation system, called FrON, is
presented. This is a pass-on system, where each of the six individual needle
segments (NiTinol rods with a diameter of 0.25 mm) are sequentially actuated by
grasping the needle segment, moving the needle segment, releasing the needle
segment, and returning to the starting position to grasp a new part of the needle
segment. The design includes a cam mechanism that functions in two directions,
to grasp the needle segment and to move the needle segment. The design was
primarily 3D-printed, and experimentally evaluated whilst varying the gelatin
stiffness utilised to represent the prostate tissue. Experiments through air
were performed as well to assess the effect of friction within the design. The
followers in the cam mechanism include springs which can be adjusted to adjust
the friction on the needle segments, this spring configuration was varied in
the evaluation as well. The experiments yielded promising and expected results;
higher gelatin stiffness or lower spring stiffness resulted in a decreased
needle propulsion efficiency. The stiffer spring configuration resulted in in a
higher average needle propulsion efficiency, with an increase in efficiency of
6.3% through air, 2.5% through a 5wt% gelatin sample, and 2.4% through a 10wt%
gelatin sample. Doubling the weight percentage in the gelatin samples
corresponded to approximately a tripling in stiffness (5.3kPa and 17 kPa). A
corresponding effect of this was observed in the results where the average
needle propulsion efficiency was approximately tripled when comparing weight
percentages in gelatin; 16.3% vs. 5.3% for the less stiff spring configuration,
and 18.8% vs. 7.7% for the stiffer spring configuration. However, areas of
improvement remain, such as the exclusion of the shrink tube that bundles the
needle segments due to breakage during the experiments. Nevertheless, this
novel combination of a 2D-Cam mechanism and a pass-on system could be a hopeful
development in the treatment of prostate cancer.