Prakash Karipoth | University of Leeds (original) (raw)

Papers by Prakash Karipoth

Advanced Engineering Materials

The field of soft robotics is rapidly progressing towards applications including; wearable electr... more The field of soft robotics is rapidly progressing towards applications including; wearable electronics, prosthetics and biomedical devices. This is leading to demand for flexible, embedded high‐performance strain sensors to deliver real‐time feedback on the static configurations and dynamic motions of these robotic devices, to ultimately enable the levels of autonomous control and structural monitoring required for intelligent manipulation. Here, Aerosol Jet Printing (AJP) technology is utilized to generate arbitrary piezoresistive strain sensor layouts on fibrous paper suitable for direct integration into elastomeric soft robots. A custom graphene nanoplatelet ink with viscosity around 2.70 cP has been formulated for optimized atomization and patterning of conductive traces via AJP. Single and multi layer printing onto different paper substrates was explored; showing influence on strain sensing performance. The nominal resistance of the printed tracks varied from 272 kΩ to 4900 kΩ ...

Journal of Magnetism and Magnetic Materials, Feb 1, 2019

Co 30 Cu 10 Pt 60 nanoparticles were prepared by a simplified polyol process devoid of any surfac... more Co 30 Cu 10 Pt 60 nanoparticles were prepared by a simplified polyol process devoid of any surfactants or capping agents. Thermo-magnetic analysis showed that the addition of 10 at. % Cu reduces the Curie temperature of Co 40 Pt 60 from 492 o C to 435 o C. The incorporation of Cu is effective in reducing the threshold ordering temperature for the A1-fcc to L1 0-fct phase transformation resulting in coercivity enhancement. Coercivity close to 10 kOe at a lower annealing temperature of 600 o C in Co 30 Cu 10 Pt 60 demonstrates that high coercivity in CoPt can be achieved in non-equiatomic compositions also. Annealing temperature dependent two phase behavior has been understood by δM studies.

Journal of Superconductivity and Novel Magnetism, Jun 10, 2014

The presence of H 2 along with an inert gas during annealing was considered as a prerequisite in ... more The presence of H 2 along with an inert gas during annealing was considered as a prerequisite in achieving high coercivity in alloys such as FePt and CoPt nanoparticles synthesized through chemical methods. CoPt nanoparticles were synthesized using a one-step polyol process without using any surfactant and annealed at various temperatures in N 2 atmosphere. The magnetic properties of Co 40 Pt 60 sample annealed at 700 o C in N 2 atmosphere showed a room temperature coercivity of 8.4 kOe. The magnetic interactions present in the samples were studied using δM measurements. The evolution of high coercivity in the samples annealed at 700 o C showed that N 2 is a cheaper alternative to the existing reducing gas mixture.

Advanced intelligent systems, Sep 1, 2021

ACS Applied Materials & Interfaces, Dec 15, 2021

This paper presents the custom-made graphite based piezoresistive strain sensor with gecko-foot i... more This paper presents the custom-made graphite based piezoresistive strain sensor with gecko-foot inspired macroscopic features realized using a Velcro tape on Ecoflex substrate. The Velcro based design provides an inexpensive and easy approach for development of soft sensor with appreciable improvement in the performance even at low strain values. The sensor demonstrated excellent response (sensitivity ~16500%, gauge factor ~3800) for 24% linear strain. The fabricated device showed a high gauge factor (>100) even for very low strain values. The sensor has been extensively characterized with a view to potentially use in soft robotics application where high-performance is needed at lower strain values. It is observed that the piezoresistive behaviour of strain sensors is governed by several factors such as the supporting elastic medium,

Journal of Colloid and Interface Science, Aug 1, 2013

FeCo alloys of various compositions with flower-like morphology were synthesized using a unique o... more FeCo alloys of various compositions with flower-like morphology were synthesized using a unique one pot polyol process. The morphology of Fe particles was cubic, whereas the FeCo particles showed flower-like morphology, with more petals for the Co rich FeCo. The average particle size varied from 120 to 155 nm depending on the composition of the alloy. The Curie temperature as determined by thermomagnetic analysis was 985°C for Fe 67 Co 33 and 939°C for the Fe 36 Co 64 samples. Their corresponding bcc to fcc phase transformation temperatures were 985 and 825°C, respectively. Coercivity up to 511 Oe was observed due to the shape anisotropy arising out of the flower-like morphology compared to the usual cubic or spherical morphologies. Post-annealing studies showed that Fe 67 Co 33 is more stable compared to other compositions.

Printed strain sensors are on high demand for flexible electronics and smart wearables. They are ... more Printed strain sensors are on high demand for flexible electronics and smart wearables. They are expected to exhibit high Figure of merits in terms of sensitivity, reliability, cost effectiveness, ease of fabrication etc. However, it is challenging to meet these attributes simultaneously. In this paper, we present a simple yet efficient method to fabricate the printed piezoresistive strain sensors with composite of carbon-based and silver-based pastes. The composite paste containing 80% and 20% by volume of carbon and silver paste was printed on poly vinyl chloride (PVC) substrate to realize the piezoresistive strain sensor over an area of 20 mm x 2 mm. The electromechanical characterization of the sensor demonstrated sensitivity of the order of 80% ($\Delta$R/R) with good repeatability and stability. The piezoresistive behaviour of presented printed composite material is owing to the modulation of electrical conductivity and conduction path by the minor inclusion of highly conductive silver fillers in a slightly less conductive carbon matrix. Finally, the strain sensor was integrated on the finger of a vinyl glove and response was monitored with finger movements. The obtained results point towards the potential use of the sensor for flexible electronics, robotics and smart wearable devices.

IEEE Transactions on Neural Systems and Rehabilitation Engineering, Jun 1, 2020

This paper presents the design and fabrication of a wearable tactile communication interface with... more This paper presents the design and fabrication of a wearable tactile communication interface with vibrotactile feedback for assistive communication. The interface is based on finger Braille, which is a simple and efficient tactile communication method used by deafblind people. It consists of a flexible piezoresistive sensor and a vibrotactile actuator integrated together and positioned at the index, middle and ring fingers of both hands to represent the six dots of Braille. The sensors were made using flexible piezoresistive material whereas the actuator utilizes electromagnetic principle by means of a flexible coil and a tiny NdFeB permanent magnet. Both were integrated to realize a Bluetooth-enabled tactile communication glove which enables deafblind people to communicate using Braille codes. The evaluation with 20 end-users (10 deafblind and 10 sighted and hearing person) of the tactile interface under standardized conditions demonstrated that users can feel and distinguish the vibration at frequencies ranging from 10Hz to 200Hz which is within the perceivable frequency range for the FA-II receptors. The results show that it took non-experts in Braille within 25s and 55s to send and receive words like "BEST" and "JOURNAL", with an accuracy of ∼75% and 68% respectively.

2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS)

ACS Applied Materials & Interfaces, 2021

Advanced Intelligent Systems, 2021

Herein, a novel tactile sensing device (SensAct) with a soft touch/pressure sensor seamlessly int... more Herein, a novel tactile sensing device (SensAct) with a soft touch/pressure sensor seamlessly integrated on a flexible actuator is presented. The squishy touch sensor is developed with custom‐made graphite paste on a tiny permanent magnet, encapsulated in Sil‐Poxy, and the actuator (15 μ‐thick coil) is fabricated on polyimide by Lithographie Galvanoformung Abformung (LIGA) micromolding method. The actuator can operate in two modes (expansion and contraction/squeeze) and two states (vibration and nonvibration). The sensor was tested with up to 12 N applied forces and exhibited ≈70% average relative resistance variation (ΔR/Ro), ≈0.346 kPa−1 sensitivity, and ≈49 ms response time with excellent repeatability (≈12.7% coefficient of variation) at 5 N. During simultaneous sensing and actuation, the modulation of coil current, due to ΔR/Ro (≈14% at 2 N force) in the sensor, allows the close loop control (ΔI/Io ≈385%) of expansion/contraction (≈69.8 μm expansion in nonvibration state and ≈111.5 μm peak‐to‐peak in the vibration state). Finally, the soft sensor is embedded in the 3D‐printed fingertip of a robotic hand to demonstrate its use for pressure mapping along with remote vibrotactile stimulation using SensAct device. The self‐controllable actuation of SensAct could provide eSkin the ability to tune stiffness and the vibration states could be utilized for controlled haptic feedback.

IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2020

Journal of Magnetism and Magnetic Materials, 2019

Science of Advanced Materials, 2014

Journal of Superconductivity and Novel Magnetism, 2014

Frontiers in Optics 2012/Laser Science XXVIII, 2012

ABSTRACT Gold coated magnetic nanoparticles are biocompatible and could be detected easily using ... more ABSTRACT Gold coated magnetic nanoparticles are biocompatible and could be detected easily using its optical properties for various biomedical applications. In this paper we report the successful synthesis of Gold coated magnetite nanoparticles and their properties.

AIP Conference Proceedings, 2011

ABSTRACT Magnetic particle flow characteristics in a microchannel were studied using Fe particles... more ABSTRACT Magnetic particle flow characteristics in a microchannel were studied using Fe particles of average sizes 25 nm and 150 nm dispersed in Dextran. The particles were subjected to different applied fields and flow rate. The results suggest the requirement of an optimum field strength and flow rate for the two different particles.

Journal of Physics and Chemistry of Solids, 2013

Size controlled cubic Fe 3 O 4 nanoparticles in the size range 90 to 10 nm were synthesized by va... more Size controlled cubic Fe 3 O 4 nanoparticles in the size range 90 to 10 nm were synthesized by varying the ferric ion concentration using oxidation method. A bimodal size distribution was found without ferric ion concentration and the monodispersity increased with higher concentration. The saturation magnetization decreased from 90 to 62 emu/g when the particle size is reduced to 10 nm. The Fe 3 O 4 nanoparticles with average particle sizes 10 and 90 nm were surface modified with prussian blue. The attachment of prussian blue with Fe 3 O 4 was found to depend on the concentration of HCl and the particle size. The saturation magnetization of prussian blue modified Fe 3 O 4 varied from 10 to 80 emu/g depending on the particle size. The increased tendency for the attachment of prussian blue with smaller particle size was explained based on the surface charge. The prussian blue modified magnetite nanoparticles could be used as a radiotoxin remover in detoxification applications.

Journal of Magnetism and Magnetic Materials, 2013

Fe nanoparticles are prepared using a unique polyol process and modified with prussian blue (PB) ... more Fe nanoparticles are prepared using a unique polyol process and modified with prussian blue (PB) at various concentrations. The presence of PB in the Fe nanoparticles are confirmed from thermal, Fourier transform infrared spectroscopy and electron microscopic analyses. The prussian blue existed on ;the surface of the nanoparticles when the concentration is 200 μM and in excess with 1000 μM. ;Fe nanoparticles are reduced in size using Pt as nucleating agent and modified with the optimum concentration of PB. The saturation magnetization decreases with the concentration of PB whereas the coercivity is influenced by the size of the Fe nanoparticles. The presence of oxide layer in Fe nanoparticles helps in the surface modification with PB. The Fe nanoparticles of particle size 53 nm modified with 200 μM of PB showed a saturation magnetization of 110 emu/g. The magnetic properties suggest that the PB modified Fe nanoparticles are better candidates for detoxification applications.

Journal of Colloid and Interface Science, 2013