Ali Eshkeiti

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.

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.

A novel flexographic printed strain gauge on paper platform

A novel flexible printed strain gauge was fabricated successfully on a flexible paper substrate using flexography printing process. Silver (Ag) ink was printed on the paper substrate as metallization layer. The performance of the printed device was investigated by subjecting the strain gauge to a 3-point bend test, with a displacement of 1 mm and 2 mm at 3 Hz operating frequency for 500 cycles. The electro-mechanical response of the strain gauge for the 1 mm displacement demonstrated an overall resistance change of 6.4 % and 6.5 % for the base resistance and bend resistance, respectively after 500 cycles of bending. Similarly an overall resistance change of 87.97 % and 28.8 % was observed for the base resistance and bend resistance, respectively after 500 cycles of bending for 2 mm displacement. The response of the fabricated strain gauge, as a function of electrical resistance, is analyzed and presented in this paper.

Fully printed and flexible piezoelectric based touch sensitive skin

A fully printed piezoelectric based touch sensitive skin has been successfully fabricated using screen printing technique. The device, consisting of a 4×4 array of printed sensors and interconnect lines, was fabricated on a flexible polyethylene terephthalate (PET) substrate, using silver (Ag) ink. Screen printed polyvinylidene fluoride (PVDF), as a piezoelectric layer, was sandwiched between the printed Ag top and bottom electrode metallization layers. The effective polarization of the printed piezoelectric PVDF layer was verified using capacitance-voltage analysis. Piezoelectric-voltage analysis demonstrated the capability of the device to generate voltage peaks as high as 10 V as well as the ability to turn on location based light-emitting diodes (LEDs). The response of the touch sensitive skin is analyzed and presented in this paper.

Screen printed flexible capacitive pressure sensor

A novel flexible fully printed capacitive based pressure sensor was designed and fabricated using screen printing technique. Silver (Ag) ink and polydimethylsiloxane (PDMS) were printed on a flexible polyethylene terephthalate (PET) substrate as metallization and dielectric layers, respectively. The capacitive response of the sensor demonstrated a percentage change of 1 % and 3.6 % for compressive forces of 0.2 MPa and 2.4 MPa, respectively when compared to the base capacitance. The response of the pressure sensor is analyzed and presented in this paper.

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.

Detection of heavy metals using fully printed three electrode electrochemical sensor

A flexible three electrode electrochemical sensor was successfully screen printed on a polyethylene terephthalate (PET) film. Silver (Ag) ink, silver/silver chloride (Ag/AgCl) ink and carbon ink was used for the counter, reference and working electrodes, respectively. The feasibility of the fully printed sensor for detecting very low concentrations of toxic heavy metal ions was demonstrated. The electrochemical impedance spectroscopy (EIS) response of the printed sensor revealed a very high sensitivity at nano molar (nM) concentration levels of lead nitrate (Pb(NO3)2) and cadmium nitrate (Cd(NO3)2). A percentage change of 18 %, in impedance, was observed for the 1 nM concentration of Pb(NO3)2 when compared with DI water. The response of the electrochemical sensor is analyzed and presented in this paper.

Screen printed MWCNT/PDMS based dry electrode sensor for electrocardiogram (ECG) measurements

This paper reports on the development of a novel printed and flexible dry electrode sensor consisting of multi-walled carbon nanotube (MWCNT)/ polydimethylsiloxane (PDMS) composite for electrocardiogram (ECG) measurements. The sensor was screen printed using silver (Ag) flake ink on flexible polyethylene terephthalate (PET) substrate. MWCNT/PDMS was then bar coated on the screen printed electrode. The capability of the printed sensor, which is conformal enough to have a better electrode-skin contact without the use of wet gel and skin preparation, was demonstrated. The response of the flexible dry electrode sensor is analyzed and presented in this paper.

Development of a Microfluidic Sensing Platform by Integrating PCB Technology and Inkjet Printing Process

A microfluidic sensing platform (MSP) for the detection of bio/chemicals has been successfully developed. Polydimethylsiloxane (PDMS)-based microfluidic channels were fabricated using master molds created with printed circuit board (PCB) technology. Silver (Ag)-based ink was employed to inkjet print interdigitated electrodes on flexible polyethylene terephthalate (PET) substrate. The printed PET substrate and PDMS were bonded to form the MSP. The capability of the fabricated MSP for detecting very low concentrations of heavy metal compounds was investigated. The electrochemical impedance spectroscopy response of the MSP revealed picomolar concentration levels of detection for mercury sulfide and cadmium sulfide. The results obtained demonstrated the feasibility of integrating conventional PCB and printing technology to create flexible MSPs for heavy metal sensing applications.

A stretchable and wearable printed sensor for human body motion monitoring

A stretchable and wearable sensor was successfully screen printed for monitoring human motions. The sensor was fabricated by printing carbon nanotube (CNT) ink on a water-soluble polymer based polyvinyl alcohol (PVA) substrate. The printed sensor was transferred onto the bicep and water was used to dissolve the sacrificial PVA layer. The sensor was subjected to flexion and extension movements of the elbow to observe the capability of the sensor for monitoring body movement. The average resistance of the sensor increased by approximately 10 % for multiple flexion movements. In addition, for extension movements, a 2 % increase was observed in the base resistance, after 10 cycles. The response of the stretchable and wearable printed sensor is analyzed and presented in this paper.