Avuthu Sai Guruva Reddy

Screen Printing of Multilayered Hybrid Printed Circuit Boards on Different Substrates

This paper reports on the successful fabrication of a multilayered hybrid printed circuit board (PCB) for applications in the consumer electronics products, medical technologies, and military equipment. The PCB was fabricated by screen-printing silver (Ag) flake ink, as metallization layer, and UV acrylic-based ink, as dielectric layer, on different substrates such as paper, polyethylene terephthalate, and glass. Traditional electronic components were attached onto the printed pads to create the multilayered hybrid PCB. The feasibility of the hybrid PCB was demonstrated by integrating an embedded microcontroller to drive an liquid-crystal display (160 × 100 pixels). In addition, the amount of the ink spreading after printing, the effect of bending on the printed lines, and the effect of the roughness of the substrates on the resistance of the printed lines was investigated. It was observed that the resistance of the lines increased by ≈1.8%, after 10000 cycles of bending, and the lowest resistance of 1.06 Ω was measured for the 600 μm printed lines on paper, which had a roughness of 0.175 μm. The advantage of fabricating PCBs on flexible substrates is the ability to fold and place the boards on nearly any platform or to conform to any irregular surface, whereas the additive properties of printing processes allow for a faster fabrication process, while simultaneously producing less material waste in comparison with the traditional subtractive processes. The results obtained show the promising potential of employing screen printing process for the fabrication of flexible and light-weight hybrid PCBs.

Printed electrochemical based biosensors on flexible substrates

A flexible substrate electrochemical biosensor was successfully printed on a polyethylene terephthalate (PET) film with silver (Ag) electrodes using silver nanoparticle based ink. The electrochemical impedance spectroscopy (EIS) response of the printed sensor for detecting low concentrations of bio/chemical species revealed a very high sensitivity at pico molar (pM) concentration levels of D-Proline, Sarcosine, Cadmium sulphide (CdS) and Potassium chloride (KCl). The impedance response of the biosensor towards these species was analyzed and is reported in this paper.

A novel fully printed and flexible capacitive pressure sensor

A novel fully printed flexible capacitive pressure sensor was fabricated using conventional screen and gravure printing techniques. The sensor was successfully printed on a flexible polyethylene terephthalate (PET) substrate with silver (Ag) nanoparticle (NP) ink as the metallization layer and polydimethylsiloxane (PDMS) as the dielectric layer. The capacitive response of the sensor demonstrated a percentage change of 5 % and 40 % for minimum and maximum detectable compressive forces of 800 kPa and 18 MPa, respectively when compared to the base capacitance of 26 pF. At the minimum detectable pressure, the stability measurements resulted in a maximum variation of ± 0.15 % from the average capacitance value of 28 pf. The response of the printed device demonstrated the feasibility of employing traditional printing techniques for the fabrication of flexible pressure sensing devices.

Gravure printed paper based substrate for detection of heavy metals using surface enhanced Raman spectroscopy (SERS)

A novel paper based surface enhancemed Raman spectroscopy (SERS) substrate was fabricated by gravure printing single and double layers of silver nanoparticle (NP) ink, with a particle size of ~20-50 nm, as metallization layer on a paper from Mitsubishi (NB-RC3GR120). The capability of the SERS substrate for detection of toxic heavy metal compounds such as mercury sulfide (HgS) was demonstrated. The SERS based response of the printed substrate produced an enhanced Raman signal when compared to target molecules adsorbed on bare paper. An enhancement factor of five orders of magnitude, due to existence of hot spots between NP, was obtained. In addition, the effect of bending of the flexible paper substrate on the intensity of the Raman spectrum was also investigated. An enhancement of 500 % in the intensity of Raman spectra was obtained for a bending of 70°. The SERS based response of the printed substrate is analyzed and presented in this paper.

Investigation of SH-SAW sensors for toxic heavy metal detection

In this study, a guided shear horizontal mode surface acoustic wave (SH-SAW) sensor with 64° YX-LiNbO3 based piezoelectric substrate and gold (Au) interdigitated electrodes (IDE) was used for the detection of toxic heavy metal compounds. A flow cell, with a reservoir volume of 3 μl, which employs inlet and outlet valves for the microfluidic chamber and polydimethylsiloxane (PDMS) based microfluidic channels, was also designed and fabricated using an acrylic material. As the SAW propagates through the substrate between input and output IDEs, a change in the velocity of the wave due to the varying concentrations of the test analytes, causes a change in the resonant frequency. This frequency based response of the SAW sensor towards mercury sulfide (HgS) and lead sulfide (PbS) demonstrated the capability of the system to detect picomolar level concentrations. The response of the SAW sensor is analyzed and presented in this paper.

Opto-electrochemical based dual detection of heavy metal compounds using a novel flow cell

An efficient sensing system that detects heavy metal compounds, by employing opto-electrochemical based dual detection technique, has been successfully developed. A novel microfluidic flow cell consisting of an inlet and outlet port with a reservoir volume of 25 μl was designed and fabricated using acrylic material. An electrochemical sensor with gold (Au) interdigitated electrodes (IDE) on a glass substrate was used for the electrical impedance spectroscopy (EIS) of various heavy metal compounds. EIS performed on cadmium sulfide (CdS) and mercury sulfide (HgS) yielded picomolar (pM) concentration detection levels. Selective detection of heavy metal compounds was made possible based on optical signals produced in the Raman emission spectra. The response of this dual detection sensing system is analyzed and presented in this paper.

Fully printed organic thin film transistors (OTFT) based flexible humidity sensors

A flexible fully printed organic thin film transistor (OTFT) was successfully fabricated and employed as a humidity sensor. The bottom gated OTFT, with width to length ratio (w/l) ratio of 26, was printed on a flexible poly ethylene terephthalate (PET) substrate. Conductive gate and dielectric layers were printed using gravure printing technique. Source and drain electrodes were deposited by means of screen printing. An active layer of pentacene, a humidity sensitive material, was deposited using inkjet printing. The current-voltage characteristics of the fully printed device were studied from 25% RH to 90% RH. A percentage change of 2000 % at 90% RH, in the drain current (ID), was registered when compared to the ID at 25% RH. The response of the fully printed sensor towards relative humidity was studied and is reported in this paper.

Gravure printed surface enhanced Raman spectroscopy (SERS) substrates for detection of toxic heavy metal compounds

A novel flexible surface enhanced Raman spectroscopy (SERS) substrate was successfully fabricated by gravure printing a silver (Ag) nanoparticle ink, with a particle size of ~20-50 nm particle size, as a metallization layer on a flexible polyethylene terephthalate film (PET). The capability of the fabricated SERS substrate to be used as a sensor for detecting toxic heavy metal compounds, such as mercury sulfide (HgS) was demonstrated. An enhancement factor of 5 orders of magnitude was obtained when compared to the intensity of a Raman spectrum of for target molecules adsorbed onto bare PET. Theis response obtained demonstrated the feasibility of thise novel SERS substrate to be used in applications for the detection of toxic heavy metals. In addition, the effect of temperature on the intensity of the Raman spectrum was also tested. The results showed an 85 % decrease in intensity at 85 °C, when compared with the intensity of te Raman sprectrum at 25 °C.

P1.9.12 Fully printed wireless LC sensor for heavy metal detection

This paper reports on the successful development of a fully printed wireless LC sensor for the detection of toxic heavy metals. The sensor, consisting of an inductor, detection coil and interdigitated electrodes (IDE) in planar form, was fabricated using screen and gravure printing technologies on a flexible polyethylene-terephthalate (PET) substrate with silver based ink as metallization. The capability of the printed LC sensor for detecting very low concentrations of toxic heavy metals was demonstrated. The wireless response of the printed LC sensor revealed a very high sensitivity at picomolar levels of cadmium sulphide (CdS) and lead sulphide (PbS).