Dinesh Maddipatla

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.

Development of a novel carbon nanotube based printed and flexible pressure sensor

A flexible carbon nanotube (CNT) based capacitive pressure sensor was developed for the detection of varying applied pressures. The sensor was successfully fabricated using the screen printing technique. Polydimethylsiloxane (PDMS) was used as a dielectric layer and it was prepared using a PDMS pre-polymer and a curing agent mixed in a 10:1 ratio. The electrode was directly screen printed using conductive CNT ink onto the PDMS. The capability of the sensor to distinguish between varying applied pressures were investigated based on its capacitive response. It was observed that the CNT-based pressure sensor produced an 8.2% change in capacitance when compared to the base capacitance, for a maximum detectable pressure of 337 kPa. A 0.021% change in capacitance per kPa and a correlation coefficient of 0.9971 was also determined for the CNT-based pressure sensor. The capacitive response of the printed sensor demonstrated the feasibility of employing CNT-based electrodes for the development of efficient, flexible and cost-effective pressure sensors for sports, military, robotic, automotive and biomedical applications.

Development of a printed impedance based electrochemical sensor on paper substrate

A novel printed impedance based electrochemical sensor has been successfully developed on a paper substrate for the detection of various bio/chemicals. This flexible analytical device was fabricated by screen printing a two electrode sensor configuration on a wax-printed chromatography paper substrate. Silver (Ag) ink was used for screen printing the working and circular electrodes. The capability of the fabricated electrochemical sensor for detecting trace concentrations of bio/chemicals such potassium chloride (KCl) and glucose (C6H12O6) was investigated. The electrical impedance spectroscopy (EIS) based response of the printed sensor revealed detection levels as low as picomolar (pM) concentrations as well as the capability of the sensor to distinguish among varying levels (pico, nano, micro and milli) of sample concentrations. The response of the developed electrochemical sensor has been analyzed and is 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.

Eutectic Ga-In liquid metal based flexible capacitive pressure sensor

A novel flexible pressure sensor has been successfully developed for detecting varying applied pressures. Polydimethylsiloxane (PDMS) and eutectic gallium indium (EGaIn) based liquid metal, as the conductive electrodes, were used to fabricate the sensor. The sensor was designed with four capacitors (C1, C2, C3 and C4) which were formed by overlapping the liquid metal based electrodes. The capability of the fabricated capacitive pressure sensor was investigated by applying varying pressures. A maximum average capacitance change of 10.14%, 11.56%, 11.57% and 11.82% was obtained for C1, C2, C3 and C4 respectively, when pressures were applied from 0.25 MPa to 1.1 MPa. A sensitivity of 0.11%/MPa and correlation coefficient of 0.9875 was obtained for the fabricated pressure sensor. The results thus demonstrated the potential of using liquid metal based electrodes for the development of flexible pressure sensors.

Rapid prototyping of a flexible microfluidic sensing system using inkjet and screen printing processes

A novel microfluidic sensing system (MSS), for the detection of bio/chemicals, has been successfully developed. Screen printing process was employed, as an additive manufacturing method, to create master molds for fabricating polydimethylsiloxane (PDMS) based microfluidic channels. Silver (Ag) ink was inkjet printed on flexible polyethylene terephthalate (PET) substrate, to form interdigitated electrodes (IDE). The MSS was created by bonding the PDMS based microfluidic channels and printed PET substrate. The electrochemical impedance spectroscopy (EIS) based response of the MSS towards heavy metal compounds: cadmium sulfide (CdS) and mercury sulfide (HgS), revealed picomolar concentration detection levels. The results obtained also demonstrated the capability of using inkjet and screen printing processes for the rapid prototyping of MSSs. The response of the developed MSS is analyzed and presented in this paper.