Angela Beninato

A Ferrofluidic Inertial Sensor Exploiting the Rosensweig Effect

In this paper, a novel device for sensing perturbations imposed to liquid media contained in a disposable housing is addressed. The device consists of a glass beaker filled with deionized water surrounding a small volume of ferrofluid; a permanent magnet is used to fix the position of the ferrofluidic mass in a compliant position and to generate spikes due to the Rosensweig effect. The effect of external stimuli on the beaker can be estimated by measuring the perturbation produced on the ferrofluidic mass. The latter strategy allows reducing drawbacks related to static friction of conventional inertial devices. The ferrofluid perturbations are monitored by two external planar coils in a differential configuration. The main features of the proposed strategy are structural decoupling between the electric read-out system and beaker housing, which allows both implementing noninvasive measurement in liquid media and making the architecture partially disposable, of low cost, and suitable for real applications.

A Low-Cost Inertial Sensor Based on Shaped Magnetic Fluids

In this paper, an inertial sensor exploiting the effect of external stimuli on a ferrofluid spike is presented. The device consists of a glass pipe filled with water where a mass of ferrofluid is fixed to the pipe wall and spike shaped by a suitable magneticfield configuration. An external perturbation will produce a movement of the spike free end, which is sensed via an infrared readout strategy. A theoretical analysis of the sensing methodology is performed, along with experiments on a laboratory-scale prototype confirming the expected behavior of the device.

Innovative ferrofluidic inertial sensor exploiting the Rosensweig effect

In this work a novel inertial sensor is presented, which can be used as a low band accelerometer, a vibration sensor or an inclinometer. The device consists of a glass plate filled with deionized water surrounding a small volume of ferrofluid; a permanent magnet is used to fix the position of the ferrofluidic mass in a compliant position. The effect of an external stimulus can be estimated by measuring the perturbation produced on the ferrofluidic mass. The static friction effect is overcame by exploiting the Rosensweig effect, caused by the magnetic field acting on the ferrofluid and producing spikes whose position is linked to the quantity to be measured. The action of the forcing quantity on the spike position is monitored by the use of two external planar coils. In the proposed device the electric read-out system is decoupled from the mechanical transducer; this makes the prototype low cost and suitable for real applications.

A Seismic Sensor Based on IPMC Combined With Ferrofluids

In this paper, a seismic sensor based on the combination of ionic polymer metal composite (IPMC) and ferrofluids is presented. The device consists of a vial, filled with ferrofluid, housing an IPMC cantilever beam sensor. Considering that the behavior (e.g., frequency response) of a beam immersed in a fluid changes with the fluid density, in this paper, a novel methodology is proposed to implement a mechanism allowing for the active tuning of the sensor specifications (such as operating range, frequency behavior, and responsivity). To such aim, the addressed methodology exploits external magnetic fields to modify the density of the ferrofluid in which the IPMC sensor is immersed. A description of the sensing methodology and the realization of the sensor prototype are given along with experimental results confirming the expected behavior of the device. Moreover, a model is presented which can be used to predict the IPMC behavior as a function of the fluid properties.

Path driving of ferrofluid samples for bio-sensing applications

In this paper a system to move a ferrofluid mass along a predefined path is presented. The mass is driven by a travelling magnetic fields generated through an electromagnetic actuation system. The pattern is defined and controlled by a dedicated LabView® interface. A description of the adopted experimental set-up is given along with some experimental results.

A inertial sensor exploiting a spike shaped ferrofluid

In this paper an inertial sensor based on the effect of an unknown perturbation on the movement of a ferrofluid spike is presented. The device consists of a glass beaker filled with deionized water and a spike shaped mass of ferrofluid. A suitable magnetic field configuration is exploited to force a spike shape to the ferrofluid. The movement of the spike free-end is sensed via an InfraRed readout strategy. A description of the adopted experimental set-up is given along with some experimental results.

A novel non-invasive implementation of pumping mechanism in pre-existing capillary

In this paper a novel pumping strategy, based on the use of a single drop of ferrofluid as the active mass and an analog driving system, is presented. The absence of mechanical moving parts and solid-inertial masses provides high reliability and the possibility to implement the pumping mechanism on pre-existing channels. Experiments dedicated to estimate the average amount of pumped liquid, the drop pressure and the capacity as function of frequency and amplitude of the driving signals, have been performed. Other measures to estimate the average amount of pumped liquid and the maximum drop pressure for a different size of the outlet tank and the amount of pumped liquid in vacuum, are achieved.

Inductive Integrated Biosensor With Extended Operative Range for Detection of Magnetic Beads for Magnetic Immunoassay

Biosensors are prominent in several areas, such as medical diagnosis, food preparation, pharmaceutical industries, and clinical analysis; high performances are required in spite of attaining accuracy, sensitivity, low cost, easy handling, and portability, but the major parameter that is always representing a challenge for biosensors is specificity. High sensitivity and specificity can be obtained by combining appropriate transduction methods together with immunoassay techniques. In this paper, integrated inductive biosensors for the magnetic immunoassay process, which use magnetic beads as markers for biomolecules, are presented with potential applications to proteins and DNA measurements. The working principle and a dedicated fabrication technology, which also embeds thermal actuation and control, are described; in particular, an improved sensing architecture is proposed here, which allows one to expand the microsensor operative field toward very low bead concentrations. The sensor characterization results are presented together with the analytical model of the transduction principle; a detection limit of approximately 300 beads has been demonstrated. The microsensor is also capable of operating by measuring up to 450 000 beads with a good linearity. Therefore, the sensor architecture proposed here has been demonstrated for wide operating field with high resolution and good linearity; the results proposed confirm the suitability of the devices developed for magnetic immunoassay applications.

Investigations into a Planar Inductive Readout Strategy for the Monitoring of Ferrofluid Carriers

Ferrofluids can be conveniently used in magnetic immune-assay techniques, such as magnetic labeling, magnetic drug targeting, hyperthermia, contrast enhancement for magnetic resonance imaging, and magnetic separation of cells. A main issue of immune-assay techniques, often adopted in lab-on-chip systems, is the transitions of the biotarget from one site to another site. This is mandatory to expose the biotarget linked to the carrier to the chemical/physical processes occurring in different sites of the system. In this paper, a strategy to control and to monitor the position of a ferrofluid mass, which can assume the role of carrier, along a predefined path is presented together with some experimental results. The behavior of the sensing readout strategy for different masses of ferrofluid, the selected path, and the time of residence of the ferrofluid carrier in each site has been investigated. A minimum residence time of 740 ms has been estimated for the LabScale prototype developed, which confirms the suitability of the proposed control and sensing strategy. Moreover, the possibility to detect the direction of the ferrofluid mass movement has been demonstrated.

Energy Harvesting from weak random vibrations: Bistable strategies and architectures for MEMS devices

This paper deals with the problem of gathering electrical energy from sources readily available in the environment. In particular we focus on vibrations that are almost ubiquitous and that very often appear as random, weak and low frequency signals. The above listed features may significantly reduce the efficiency of traditional linear resonant and therefore alternative innovative strategies need to be explored. In this paper we present some devices that have been analytically modeled and experimentally verified for tackling this issue. The basic idea is centered on the use of bistable oscillators to realize vibration harvesters that can scavenge energy from broadband, weak, random vibrations: this idea will be expanded here toward some solutions where bistability is obtained by using magnets but also where it descends from purely mechanical devices. A brief review on solutions developed that exploit magnetic and non magnetic strategies for obtaining bistability is presented, finally the issue of MEMS fabrication for the devices conceived will be discussed.