Transducer | EPFL Graph Search

A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one form of energy to another is known as transduction. Types

Mechanical transducers, so-called as they convert physical quantities into mechanical outputs or vice versa;
Electrical transducers however convert physical quantities into electrical outputs or signals. Examples of these are: ** a thermocouple that changes temperature differences into a small voltage; ** a linear variable differential transformer (LVDT), used to measure displacement (position) changes by means of electrical signals.

Sensors, actuators and transceivers Transducers can be cate

Deeply implanted medical device based on a novel ultrasonic telemetry technology

Michela Peisino

Medical devices have gone a long way since their beginning. In the last decades, the trend has been towards Implanted Medical Devices (IMDs). The technology evolution has provided the necessary tools for longer-term, less invasive devices. Several devices for sensing and actuation are commercially available and ease therapy management, while preserving the patient’s life quality. An ideal implant would integrate both sensing and actuating possibilities in a feedback loop, thus achieving optimum therapy. To reach this goal, several challenges remain, in particular concerning power supply and miniaturization. Solving these issues would open new possibilities and allow applications which are not possible yet: better diagnosis could be achieved wherever a continuous, long-term monitoring of physiological parameters in real life conditions is required. For instance, smaller and deeper implanted devices would allow deploying several IMDs in the body, achieving a Body Sensor Network (BSN). Beside therapy, implants could be used for diagnosis in populations at risk. Furthermore, minimal invasive implants would greatly improve medical research, by allowing closer observation, thus helping to understand physiological mechanisms. This thesis describes the author’s contribution to the development of a novel IMD concept, proposed within the European FP7 project ULTRAsponder. The author focused on the integration aspects in the design and manufacturing process of the novel implantable device platform: definition of the technical specifications, assessment of appropriate commercial components, geometrical placement of the Printed Circuit Boards (PCBs) inside the casing, choice of a suitable housing material, and assessment of its effect on the energy transmission. The target is a generic BSN node, which can be implanted wherever needed on a long-term basis and which can operate autonomously. Key features of the proposed system include remote powering of the implanted device and communication with an external Control Unit (CU) by backscattering modulation. For both energy and data transfer, an ultrasonic carrier is used instead of Electromagnetic (EM) waves because it is compatible with Magnetic Resonance Imaging (MRI) and does not interfere with EM emitters like mobile phones and electronic equipment. It also proved to be more efficient than the use of Radio Frequency (RF) waves or magnetic induction to reach deep implants and when using small transducers. The user requirements and the technical constraints towards an optimal implant were evaluated and the characteristics of the proposed system were defined. Appropriate commercial components and emerging technologies were identified, which allowed the development of the device. The originality of this work lies in the integration of different technologies, components and scientific approaches into a novel, promising IMD. In particular, the challenge of achieving an ultrasonic link through a standard medical grade titanium casing is addressed. Titanium casings are the golden standard for biocompatible device housing, but they have a strong influence on ultrasonic energy transfer. Successful integration of ultrasonic transmission and titanium casing ensures the ability of the proposed device to be industrially exploited and commercialized. A demonstrator implant and an external CU have been manufactured, focusing on energy transfer, signal treatment, and backscattering. A commercial, rather large housing was used, in order to demonstrate the industrial viability of the device. In vitro tests validated the energy transfer and the communication between the CU and the Transponder (TR), as well as the user interface. Assessment in real conditions is achieved by in vivo tests on pigs. Functionality was proved, however at a much smaller distance than intended. Future work includes optimization of the ultrasonic transfer, integration of the sensing circuitry, and miniaturization of the resulting device.

EPFL2013

Analytical design and optimization of ultrasonic vibrational transducers for spinal surgery

John Murphy

Just about every other technical publication you pick up these days makes sweeping statements concerning the pressures on scientists, engineers, and industries as a whole to get to market in less time, with an improved, less expensive product. I am reminded of a slogan used rather ubiquitously by a prior employer : Cheaper, Faster, Better. The mention of this race has become almost blase for most, but for the individuals taking the brunt of the pressure, can be disconcerting if not outright painful. Expected to live up to this ambition, the design engineer is faced with the fact that the door is closing on antiquated methods of trial and error engineering. Unfortunately, most individuals have not been equipped with the necessary skills to enact a more intelligent design process and in many cases when the skills are present, industry, a bit paradoxically, is wary of expending the time and resources needed to fit into this new streamlined paradigm. This thesis could be considered as a case study of a somewhat mature technology coming to grips with this new rushed reality. Typical design methods for ultrasonic transducers, while based on analytical models, have relied heavily on building a transducer from quarter wave segments that have somewhat known characteristics. Prototypes are built, tested and modified until the desired results are obtained. Advances have been made to this method with the introduction of finite element softwares that allow modeling without realizing a prototype. The finite element methodology also permits a limited amount of system optimization, and while this is a definite improvement, it can still take months to realize an acceptable design. In this work, we draw on the analytical models, but abandon the quarter wave approach. We also use finite elements, to a limited extent, to validate results obtained from the analytical models, but do not attempt to use the finite element analysis to perform optimizations. On the contrary, a novel optimization method is developed which uses the analytical models to calculate values for the various cost functions necessary to optimize a transducer and its drive electronics. In this way, system parameters are left free to vary in the search for a maximum or minimum solution. While some systems are not candidates for system optimization as a means to get to market faster with a better product, this is not the case for ultrasonic transducers. The design of ultrasonic transducers is an application that begs for models, for optimization, and characterization. The investment made here in understanding the mathematical models, and in the development of optimization routines and softwares has allowed for a modified method of development for ultrasonic handpieces and their drive electronics. This thesis shows that, given a set of design specifications, the design of a transducer can be done in a very short period of time, a few days, even-and furthermore, the resulting design will function as predicted by the simulations. This work presents analytical models for the transducers elements with analysis and discussion. It then introduces a new method of optimization that is well adapted to optimizing the transducers as well as the drive electronics. The control electronics and a simple method of transducer control, which allow for the operation of the system for testing purposes, are also laid out.

EPFL2007

Exploration of micro-acoustic spectrometry techniques

Florian Fernand Hartmann

This master’s thesis aimed at exploring the field of micro-acoustic spectrometry using surface acoustic waves. The objectives of this project were to design and fabricate a platform for the detection and characterization of bioentities. Design of a delay line based on the experience and knowledge of the ANEMS group and on investigation of existing solutions was performed. Different configurations and types of transducers were simulated to come up with some meaningful designs for fabrication. The devices were fabricated in the clean rooms at EPFL with a specific process flow used for the suspended structures. Extensive simulation of bidirectional and unidirectional transducers were carried out in order to understand their behavior and to be able to use them as the elements of the sensing platform. Setbacks prevented the completion of the fabrication and no real measurements could be done before the end of this project, but the simulations gave nice perspectives for the targeted application. The potential of surface acoustic waves to detect modifications in the elasticity or the density of a material could be witnessed in the last simulations.

2022