Bio Medical & personal assistance

Categories

  • (34)
    • (9)
  • (3)
  • (138)
    • (18)
    • (7)
    • (2)
    • (5)
    • (8)
    • (17)
    • (1)
    • (100)
    • (7)
  • (12)
    • (7)
    • (1)
    • (1)
  • (4)
  • (152)
    • (19)
    • (2)
    • (5)
    • (111)
    • (34)
  • (10)
    • (4)
  • (55)
    • (14)
    • (3)
    • (7)
  • (61)
    • (17)
    • (5)
    • (24)
    • (7)
  • (11)
    • (1)
    • (2)
    • (1)
    • (1)
    • (1)
  • (13)
  • (12)
    • (4)
    • (6)

AC magnetic field detection system applied to motion tracking

12 February 2010

In the context of motion tracking and virtual reality, there is a strong need for sensors to monitor the motion of a moving object. These sensors are characterised by their performances (ranges, accuracy, drifts, and susceptibility to the ambient environment) and embedded (small size, light weight). The magnetic technology compared to the mechanical or optical solution allows the working without structural skeleton composed of links interconnected by monitored joints and with possible optical shadows.

Long stroke/High resolution tip tilt mechanism

19 June 2023

Multi degree of freedom (dof) mechanisms are widely required into micro or macro manipulation fields as well as in optronics functions. Commonly available mechanisms may be divided into two main categories. The first is industrial robots (serial or parallel). These offer large range of motion, in rotation and translation. Their resolution is usually limited in the sub-millimeter range. The second category achieves very high resolution motion (sub-nanometer) but is limited to a few decades of microns. A way to combine both long stroke and resolution is to use piezo motors into multi dof mechanisms. The aim of this paper is to present a combination of both advantages into a low volume tripod actuator. The Tripod Actuator by Cedrat Technologies (TrAC) is a 3 dof mechanism offering +/-35° rotation around X and Y axis and a 10mm Z translation stroke into a low volume of Ø50x50mm.

Frequency Dependence of Mouse Brain Tissue Stiffness Measured in vivo with MR Elastography

19 June 2023

Magnetic resonance elastography (MRE) is a non-invasive imaging technique for quantitative measurement of the mechanical properties of biologic tissue in vivo [1]. The clinical interest in MRE has largely been driven by the direct relationship between tissue health and stiffness. As a result, MRE may provide significant clinical value for the non-invasive diagnosis of pathology and response to therapy by tracking tumor development and monitoring therapeutic response. MRE may also have considerable value in the development of treatment protocols in pre-clinical, rodent models of cancer. Because of cost and versatility, the mouse, in particular, is widely employed in oncologic studies. To resolve its small anatomic features, MRE experiments in mice must be performed with high driving frequencies (>600 Hz). However, high-frequency waves exhibit increased attenuation, reducing wave penetration depth and making it more difficult to impart motion deep into tissue with sufficient amplitude to overcome background noise. Also, biologic tissue is viscoelastic; hence, its response to load depends on the driving frequency. Recent MRE studies in mouse brain have been performed in high-field scanners (7 – 11.7T) at single driving frequencies of 1000 and 1200 Hz [2,3]. Here, we perform elastography in mouse brain tissue at 4.7T and report viscoelastic material properties over a range of driving frequencies (600 – 1800 Hz).

Design of a dynamic tribometer applied to piezo inertia drive motors

7 November 2019

In Inertia Drive Motors, generated motion is based on stick-slip principle. Current analytical models are predictive enough to calculate qualitatively their optimal performances, such as maximal step size and speed, with relatively few input parameters. Butn they do not take into account the contact life and temporal evolution of parameters as friction factor all along lifetime of IDM. So analytical models reach their limitswhen precise predictions are necessary.

Design of a dynamic tribometer applied to piezoelectric Inertia Drive Motors – In situ exploration of stick-slip principle

19 June 2023

In Inertia Drive Motors, generated motion is based on stick-slip principle. Current analytical models are predictive enough to calculate qualitatively their optimal performances, such as maximal step size and speed, with relatively few input parameters. But, they do not take into account the contact life and temporal evolution of parameters as friction factor all along lifetime of IDM. So, analytical models reach their limits when precise predictions are necessary. This investigation aims at understand wear mechanisms to model temporal evolution of friction. Such an understanding requires the reconstitution of the contact life through the evaluation of 1st and 3rd body flows. To do so, a new IDM-representative tribometer is designed. First bodies – coated TA6V and polymer – are not see-through. They are replaced alternatively by an intermediate transparent first body to observe the contact dynamically and in-situ. Friction factor, step size and mean speed are also measured. Preliminary results shows that wear profiles from real IDM and tribometer are similar. Direct observations bring out particles of TA6V coating are firstly snatched, then moves in contact and finally trigs others particle detachments.

Comparison of Viscoelastic Property Characterization of Plastisol Phantoms with Magnetic Resonance Elastography and High-Frequency Rheometry

7 November 2019

This study aims at evaluating Magnetic Resonance Elastography (MRE) as a reliable technique for the characterization of viscoelastic properties of soft tissues. Three phantoms with different concentrations of plastisol and softener were prepared in order to mechanically mimic a broad panel of healthy and pathological soft tissues. Once placed in a MRI device, each sample was excited by a homemade external driver, inducing shear waves within the medium. The storage (G’) and loss (G’’) moduli of each phantom were then reconstructed from MRE acquisitions over a frequency range from 300 to 1,000 Hz, by applying a 2D Helmholtz inversion algorithm. At the same time, mechanical tests were performed on four samples