arXiv subjects

Prosenjit Sen

Publications and source records attributed to Prosenjit Sen.

4 recordsLinked to original sources

arXiv2023

Laser Etch Enabled Active Embedded Microfluidic Cooling in $\beta$-Ga$_2$O$_3$

We demonstrate active embedded microfluidic cooling in $\beta$-Ga$_2$O$_3$. We employ a cost-effective infra-red laser etch setup to achieve controlled etching of micro-channels in 500 um thick $\beta$-Ga$_2$O$_3$ substrate. The micro-channels are about 210 um deep and 340 um wide. Resistive heating is used as proof-of-concept. At a water flow rate of 50 ml/min, a 50% reduction in surface temperature from ~140$^\circ$C to ~72$^\circ$C is achieved for 3.5 W of input power. The experimental observations are backed by thermal simulation. This work is expected to lead to a new paradigm in thermal management in emerging $\beta$-Ga$_2$O$_3$ devices.

physics.app-ph↗

arXiv2021

Suppression of Droplet Breakage by Early Onset of Interfacial Instability

Hypothesis: Interfacial instabilities cause undesirable droplet breakage during impact. Such breakage affects many applications, such as printing, spraying, etc. Particle coating over a droplet can significantly change the impact process and stabilize it against breakage. This work investigates the impact dynamics of particle-coated droplets, which mostly remains unexplored. Experiments: Particle-coated droplets of different mass loading were formed using a volume addition. Then the prepared droplets were impacted on superhydrophobic surfaces, and their dynamics were recorded using a high-speed camera. Findings: We report an intriguing phenomenon where interfacial fingering instability helps suppress breakage in particle-coated droplets. This island of breakage suppression, where the droplet maintains its intactness upon impact, appears within a regime of Weber numbers where droplet breakage is inevitable. The onset of fingering instability in particle-coated droplets is observed at much lower impact energy, around two times less than the bare droplet. The instability is characterized using the rim Bond number. The instability suppresses breakage because of the higher losses associated with the formation of stable fingers. Such instability can also be seen in Leidenfrost surfaces and dust/pollen-covered surfaces, making it useful in many applications related to self-cleaning.

physics.flu-dyn↗

arXiv2020

Reduced Graphene Oxide Tattoo as Wearable Proximity Sensor

The human body is punctuated with wide array of sensory systems that provide a high evolutionary advantage by facilitating formation of a detailed picture of the immediate surroundings. The sensors range across a wide spectrum, acquiring input from non-contact audio-visual means to contact based input via pressure and temperature. The ambit of sensing can be extended further by imparting the body with increased non-contact sensing capability through the phenomenon of electrostatics. Here we present graphene-based tattoo sensor for proximity sensing, employing the principle of electrostatic gating. The sensor shows a remarkable change in resistance upon exposure to objects surrounded with static charge on them. Compared to prior work in this field, the sensor has demonstrated the highest recorded proximity detection range of 20 cm. It is ultra-thin, highly skin conformal and comes with a facile transfer process such that it can be tattooed on highly curvilinear rough substrates like the human skin, unlike other graphene-based proximity sensors reported before. Present work details the operation of wearable proximity sensor while exploring the effect of mounting body on the working mechanism. A possible role of the sensor as an alerting system against unwarranted contact with objects in public places especially during the current SARS-CoV-2 pandemic has also been explored in the form of an LED bracelet whose color is controlled by the proximity sensor attached to it.

cs.HC↗

arXiv2019

Drop Impact Printing

Hydrodynamic collapse of a central air-cavity during the recoil phase of droplet impact on a superhydrophobic sieve leads to satellite-free generation of a single droplet through the sieve. Two modes of cavity formation and droplet ejection was observed and explained. The volume of the generated droplet scales with the pore size. Based on this phenomenon, we propose a new drop-on-demand printing technique. Despite significant advancements in inkjet technology, enhancement in mass-loading and particle-size have been limited due to clogging of the printhead nozzle. By replacing the nozzle with a sieve, we demonstrate printing of nanoparticle suspension with 71% mass-loading. Comparatively large particles of 20 micrometer diameter were dispensed in droplets of 80 micrometer diameter. Printing was performed for surface tension as low as 32 mNm-1 and viscosity as high as 33 mPa-s. In comparison to existing techniques, this new way of printing is widely accessible as it is significantly simple and economical.

physics.app-ph↗