Sai Guruva Reddy Avuthu

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.

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.

A novel self-supported printed flexible strain sensor for monitoring body movement and temperature

A novel self-supported printed strain sensor was successfully screen printed using silver (Ag) ink on a water-soluble sacrificial polymer layer, which was pre-coated on a flexible polyethylene terephthalate (PET) film, for monitoring body movement. The printed sensor, along with the polymer layer, was peeled off the PET film and transferred onto the wrist. Then the sacrificial layer was dissolved with water. The capability of the printed sensor for monitoring the movement of the body was investigated by subjecting the sensor towards different inward and outward bending of the wrist. The average resistance of the sensor decreased by approximately 10 % for multiple inward bending and attained its base resistance, of 29 Ω, when the wrist was brought back to the original relaxed position. It was also observed that the resistance of the sensor increased by 0.1 Ω when the temperature was increased by 1 °C, thereby demonstrating the feasibility of the device to be used as a temperature sensor. The design, fabrication and response of the self-supported printed strain sensor is analyzed and presented in this paper.

Detection of heavy metal ions using screen printed wireless LC sensor

This paper reports on the successful development of a fully printed wireless LC sensor for the detection of toxic heavy metal ions. The LC sensor, consisting of inductors and interdigitated electrodes (IDE) in planar form, was screen printed on flexible polyethylene-terephthalate (PET) substrate with silver (Ag) ink as metallization layer. Palladium nanoparticles (Pd NP) were drop casted onto the IDEs as sensing layer. The resonant frequency of the LC sensor was remotely monitored by measuring the reflection coefficient (S11) of a detection coil (planar inductor). The change in resonant frequency of the LC sensor towards varying concentrations of mercury (Hg2+) and lead (Pb2+) ions, revealed micro molar detection levels. The response of the printed wireless LC sensor is analyzed and presented.

Detection of 2,4-dinitrotoluene (DNT) using gravure printed surface enhancement Raman spectroscopy (SERS) flexible substrate

In this work, gravure printing was used to fabricate a thin film of silver (Ag) nanoparticle ink on flexible polyethylene terephthalate (PET) sheet as an efficient surface enhanced Raman spectroscopy (SERS) substrate. The printed SERS substrate was used for the detection of an explosive organic compound: 2,4-dinitrotoluene (DNT), in vapor phase. An enhancement factor of four, in the intensity of the Raman spectrum of DNT vapor, was observed when compared to target molecules absorbed on bare PET. An increase in temperature, from 25 °C to 65 °C, demonstrated an 85 % decrease in the intensity of the Raman signal. The results obtained show the capability of the printed SERS substrate to be used in applications for the detection of explosive organic compounds.

Development of a novel printed flexible microfluidic sensing platform based on PCB technology

A novel printed microfluidic sensing platform (MSP) has been successfully developed for the detection of bio/chemicals. Interdigitated electrodes (IDE) were fabricated by inkjet printing silver (Ag) based ink on flexible polyethylene terephthalate (PET) substrate. For the first time, printed circuit board (PCB) technology was used to create master molds for polydimethylsiloxane (PDMS) based microfluidic channels. The printed PET substrate and PDMS microfluidic channels were bonded to form the MSP. The capability of the fabricated MSP for detecting very low concentrations of bio/chemicals was demonstrated. The electrical impedance spectroscopy (EIS) based response of the system revealed picomolar detection levels as well as the feasibility of integrating conventional PCB and printing technology to create flexible MSPs for various bio/chemical sensing applications. The response of the developed MSP is analyzed and presented in this paper.