Analytical Modeling of a New Compliant Microsystem for Atherectomy Operations

Abstract

This work offers a new alternative tool for atherectomy operations, with the purpose of minimizing the risks for the patients and maximizing the number of clinical cases for which the system can be used, thanks to the possibility of scaling its size down to lumen reduced to a few tenths of mm. The development of this microsystem has presented a certain theoretical work during the kinematic synthesis and the design stages. In the first stage a new multi-loop mechanism with a Stephenson’s kinematic chain (KC) was found and then adopted as the so-called pseudo-rigid body mechanism (PRBM). Analytical modeling was necessary to verify the synthesis requirements. In the second stage, the joint replacement method was applied to the PRBM to obtain a corresponding and equivalent compliant mechanism with lumped compliance. The latter presents two loops and six elastic joints and so the evaluation of the microsystem mechanical advantage (MA) had to be calculated by taking into account the accumulation of elastic energy in the elastic joints. Hence, a new closed form expression of the microsystem MA was found with a method that presents some new aspects in the approach. The results obtained with Finite Element Analysis (FEA) were compared to those obtained with the analytical model. Finally, it is worth noting that a microsystem prototype can be fabricated by using MEMS Technology classical methods, while the microsystem packaging could be a further development for the present investigation.

A Cantilever-Based Piezoelectric MEMS for Arbitrary XY Path Generation

“…As a proof of the microdevice's ability to make the tip trace arbitrary trajectories, many trajectories relevant in the field of micro-invasive surgery as well as surface scanning were considered. Circular, elliptical, spiral and cycloidal trajectories are particularly suitable in atherectomy operations to remove obstructions and calcifications developing within arterial walls [18,47] so long as they entail a low risk of perforating the lumen walls. Lissajous and cosinusoidal/linear trajectories are used as alternative scanning methods in atomic force microscopes (AFM) [48].…”

“…This mechanism was successfully exploited to implement piezoelectric micropositioning devices that provide pure translational motion of the jaws and allow to simplify the geometry of the whole system [15][16][17]. Lately, a microgripper for atherectomy operations based on Stephenson's kinematic chain has been proposed [18]. The tip motion of the microgripper was designed to avoid perforating the lumen walls while removing obstructions.…”

Theoretical, numerical, and experimental investigation on the compliance and natural frequency of sinusoidal flexure hinges

“…Compliant mechanisms have the advantages of high precision, no friction, no need for lubrication, and cost reduction. So, they are widely used in optical fiber alignment equipment, 1 medical instruments, 2,3 micro/nano‐manipulation 4,5 and micro‐electro mechanical systems (MEMS) 6 . According to the distribution pattern of compliance in the mechanisms, they can be divided into three types: lumped compliant mechanisms, distributed compliant mechanisms, and hybrid compliant mechanisms.…”

First results on torque estimation by FEA and experimental analysis in a novel CSFH-based microgripper

“…where τ stands for the comb-drive's torque, while k and ϑ indicate the CSFH stiffness coefficient and the microactuator's angular displacement, respectively. As a first approximation, by considering CSFHs homogeneous, linear elastic beams with uniform, rectangular cross sections and assuming the bending moment as constant, it is possible to estimate the stiffness coefficient k [16][17]:…”