Memoon Sajid

Hybrid Surface Acoustic Wave- Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PEDOT:PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films’ characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

Bio-compatible organic humidity sensor transferred to arbitrary surfaces fabricated using single-cell-thick onion membrane as both the substrate and sensing layer.

A bio-compatible disposable organic humidity sensor has been fabricated that can be transferred to any arbitrary target surface. Single cell thick onion membrane has been used as the substrate while it also doubles as the active layer of the sensor. Two different types of sensors were fabricated. In type-1, the membrane was fixed into a plastic frame with IDT patterns on one side while the other side was also exposed to environment. In type-2, onion membrane was attached to a glass substrate with one side exposed to environment having an IDT screen-printed on top of it. The electrical output response of the sensors showed their ability to detect relative humidity between 0% RH and 80% RH with stable response and good sensitivity. The impedance of the sensors changed from 16 MΩ to 2 MΩ for type-1 and 6 MΩ to 20 KΩ for type-2. The response times of type-1 and type-2 were ~1 and 1.5 seconds respectively. The recovery times were ~10.75 seconds and ~11.25 seconds for type-1 and type-2 respectively. The device was successfully transferred to various randomly shaped surfaces without damaging the device.

All-printed highly sensitive 2D MoS 2 based multi-reagent immunosensor for smartphone based point-of-care diagnosis

Immunosensors are used to detect the presence of certain bio-reagents mostly targeted at the diagnosis of a condition or a disease. Here, a general purpose electrical immunosensor has been fabricated for the quantitative detection of multiple bio-reagents through the formation of an antibody-antigen pair. The sensors were fabricated using all printing approaches. 2D transition metal dichalcogenide (TMDC) MoS2 thin film was deposited using Electrohydrodynamic atomization (EHDA) on top of an interdigitated transducer (IDT) electrode fabricated by reverse offset printing. The sensors were then treated with three different types of antibodies that were immobilized by physisorption into the highly porous multi-layered structure of MoS2 active layer. BSA was used as blocking agent to prevent non-specific absorption (NSA). The sensors were then employed for the targeted detection of the specific antigens including prostate specific antigen (PSA), mouse immunoglobulin-G (IgG), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). IgG was then selected to test the sensors for point of care (POC) diagnosis through a specially designed electronic readout system for sensors and interfacing it with a smartphone using Bluetooth connection. The sensors showed promising performance in terms of stability, specificity, repeatability, sensitivity, limit of detection (LoD), and range of detection (RoD).

3D printing for soft robotics – a review

Abstract Soft robots have received an increasing attention due to their advantages of high flexibility and safety for human operators but the fabrication is a challenge. Recently, 3D printing has been used as a key technology to fabricate soft robots because of high quality and printing multiple materials at the same time. Functional soft materials are particularly well suited for soft robotics due to a wide range of stimulants and sensitive demonstration of large deformations, high motion complexities and varied multi-functionalities. This review comprises a detailed survey of 3D printing in soft robotics. The development of key 3D printing technologies and new materials along with composites for soft robotic applications is investigated. A brief summary of 3D-printed soft devices suitable for medical to industrial applications is also included. The growing research on both 3D printing and soft robotics needs a summary of the major reported studies and the authors believe that this review article serves the purpose.

Liquid assisted exfoliation of 2D hBN flakes and their dispersion in PEO to fabricate highly specific and stable linear humidity sensors

A highly specific and sensitive linear humidity sensor has been fabricated using a dispersion of 2D hexagonal boron nitride (hBN) flakes in polyethylene oxide (PEO). Bulk hBN powder was exfoliated via liquid-assisted mechanical exfoliation to achieve few-layered 2D nano-flakes with thicknesses in the range of 3–4 nm. PEO was used as the polymer matrix to disperse the hBN flakes evenly throughout the suspension. An interdigitated transducer (IDT) electrode pair fabricated via reverse off-set printing using silver nanoparticles ink (AgNPs) on a piezoelectric LiNbO3 substrate serves as the transducing portion of the sensor. Electrohydrodynamic atomization was used to spray a uniform thin film of the active composite material onto the sensor electrodes. All the fabrication methods used are compatible with printed electronics approaches and are suitable for mass production. The sensors show excellent stability for up to 40 days of testing. The sensitivity of the near-linear sensors was ∼24 kΩ/%RH, which is better than most of the previously reported studies. The sensors showed response and recovery times of 2.6 s and 2.8 s, respectively. The selectivity of the sensors was tested by exposing the sensors to O2, N2, and CH4 gases in addition to humidity and the results showed no effect of the other gases on the sensors output. The fabricated sensors based on the 2D hBN/polymer composite can be employed in high-end target specific applications requiring accurate and high performance humidity sensors.

Remote monitoring of environment using multi-sensor wireless node installed on quad-copter drone

Environmental monitoring and radiation detection in the vicinity of nuclear power plants is a tricky task and there is a potential radiation exposure hazard for the human beings and wildlife. To remotely monitor the environmental parameters like humidity, temperature, radiation, etc., the sensors were installed on a remotely controlled quad-copter drone. A GPS was also installed to determine the location and height of the drone for the particular parameters. An Arduino Yun based circuit interface was designed and was mounted on the drone as a multi-sensor standalone wireless node. Built-in Wi-Fi of the Yun board was used to transmit all the data to the base station. Android based application was developed to communicate with the node and display the data in real time along with logging it to device. Furthermore, a humidity and a temperature sensor were fabricated in through printed electronics methods and were also mounted on the drone with aim to replace commercial sensors. The aim of this research work was to build a system that can be used in future for monitoring of nuclear power plant vicinity and study the changes in environmental parameters in that region.