Mohammed Asadullah Khan

Magnetic Tactile Sensor for Braille Reading

We report a biomimetic magnetic tactile sensor for reading Braille characters. The sensor consists of magnetic nanocomposite artificial cilia implemented on magnetic micro sensors. The nanocomposite is produced from the highly elastic polydimethylsiloxane and iron nanowires that exhibit a permanent magnetic behavior. This design enables remote operation and does not require an additional magnetic field to magnetize the nanowires. The highly elastic nanocomposite is easy to pattern, corrosion resistant, and thermally stable. The tactile sensors can detect vertical and shear forces, which allows recognizing small changes in surface texture, as in the case of Braille dots. The six dots of a braille cell are read from top to bottom with a tactile sensor array consisting of four elements and 1 mm long nanocomposite cilia.

Magnetic Nanocomposite Cilia Energy Harvester

An energy harvester capable of converting low-frequency vibrations into electrical energy is presented. The operating principle, fabrication process, and output characteristics at different frequencies are discussed. The harvester is realized by fabricating an array of polydimethylsiloxane-iron nanowire nanocomposite cilia on a planar coil array. Each coil element consists of 14 turns and occupies an area of 600 μm. The cilia are arranged in a 12×5 array, and each cilium is 250 μm wide and 2 mm long. The magnetic characteristics of the fabricated cilia indicate that the nanowires are well aligned inside of the nanocomposite, increasing the efficiency of energy harvesting. The energy harvester occupies an area of 66.96 mm2 and produces an output rms voltage of 206.47 μV when excited by a 40 Hz vibration of 1 mm amplitude.

Magnetic Composite Hydrodynamic Pump With Laser-Induced Graphene Electrodes

A polymer-based magnetohydrodynamic pump capable of actuating saline fluids is presented. The benefit of this pumping concept to operate without any moving parts is combined with simple and cheap fabrication methods and a magnetic composite material, enabling a high level of integration. The operating principle, fabrication methodology, and flow characteristics of the pump are detailed. The pump electrodes are created by laser printing of polyimide, while the permanent magnet is molded from an NdFeB powder–polydimethylsiloxane (PDMS) composite. The cross section area of the pump is 240 mm2. The electrode length is 5 mm. The magnetic characteristics of the NdFeB–PDMS composite indicate high degree of magnetization, which increases the pump efficiency. Using a saline solution similar to seawater, the pump produces 3.4 mm/s flow velocity at a voltage of 7.5 V and a current density of 30 mA/cm2.

Laser printed graphene on polyimide electrodes for magnetohydrodynamic pumping of saline fluids

An efficient, scalable pumping device is reported that avoids moving parts and is fabricated with a cost-effective method. The magnetohydrodynamic pump has electrodes facilely made by laser printing of polyimide. The electrodes exhibit a low sheet resistance of 22.75 Ω/square. The pump is implemented in a channel of 240 mm2 cross-section and has an electrode length of 5 mm. When powered by 7.3 V and 12.43 mA/cm2, it produces 13.02 mm/s flow velocity.

A single magnetic nanocomposite cilia force sensor

The advancements in fields like robotics and medicine continuously require improvements of sensor devices and more engagement of cooperative sensing technologies. For example, instruments such as tweezers with sensitive force sensory heads could provide the ability to sense a variety of physical quantities in real time, such as the amount and direction of the force applied or the texture of the gripped object. Force sensors with such abilities could be great solutions toward the development of smart surgical tools. In this work, a unique force sensor that can be integrated at the tips of robotic arms or surgical tools is reported. The force sensor consists of a single bioinspired, permanent magnetic and highly elastic nanocomposite cilia integrated on a magnetic field sensing element. The nanocomposite is prepared from permanent magnetic nanowires incorporated into the highly elastic polydimethylsiloxane. We demonstrate the potential of this concept by performing several experiments to show the performance of the force sensor. The developed sensor element has a 200 μm in diameter single cilium with 1:5 aspect ratio and shows a detection range up to 1 mN with a sensitivity of 1.6 Ω/mN and a resolution of 31 μN. The simple fabrication process of the sensor allows easy optimization of the sensor performance to meet the needs of different applications.

Magnetic composite based magneto hydrodynamic pump

In lab on chip systems, fluids need to be transported from one part of the system to another and they also need to be agitated for mixing with other fluids/reagents.

Fabrication and characterization of magnetic composite membrane pressure sensor

This paper describes a magnetic field powered pressure sensor, which comprises a coil array and a magnetic composite membrane. The composite membrane is made by embedding a ribbon of the amorphous soft magnetic alloy Vitrovac®, in a 17 mm × 25 mm × 1.5 mm Polydimethylsiloxane (PDMS) layer. PDMS is chosen for its low Youngs modulus and the amorphous alloy for its high permeability. The membrane is suspended 1.5 mm above a 17×19 array of microfabricated planar coils. The coils are fabricated by patterning a 620 nm thick gold layer. Each coil occupies an area of 36000 μm2 and consists of 14 turns. The sensor is tested by subjecting it to pressure and simultaneously exciting it by a 24 A/m, 100 kHz magnetic field. A pressure change from 0 kPa to 5.1 kPa, results in a 5400 ppm change in the voltage output.