Amer Abdulmahdi Chlaihawi

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.

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.

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.

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.

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.

Development of flexible dry ECG electrodes based on MWCNT/PDMS composite

Flexible dry electrode based on multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composite, for monitoring electrocardiogram (ECG) signals, has been developed. The dry ECG electrode was fabricated by screen printing silver (Ag) ink on flexible polyethylene terephthalate (PET) substrate, followed by bar coating of MWCNT/PDMS composite. The performance of the fabricated device was investigated by measuring ECG signals using printed dry electrodes with radii varying from 8 mm to 16 mm. The results were compared with a traditional wet Ag/AgCl ECG electrode (T716). It was observed that the dry ECG electrode, with the largest area, demonstrated better performance, in terms of signal intensity and correlation, when compared to the traditional wet ECG electrode. The response of the dry ECG electrodes are analyzed and presented in this paper.

Novel screen printed and flexible low frequency magneto-electric energy harvester

A novel low frequency magneto-electric energy harvester was developed for application in microelectronic devices. The energy harvester was fabricated by screen printing polyvinylidene fluoride (PVDF) ink, as a piezoelectric layer, on flexible and magnetic Metglas® substrate. Silver (Ag) ink, as top electrode layer, was then deposited on the printed PVDF layer using screen printed technique. The performance of the printed device was investigated by measuring the DC output voltage and maximum power delivered at varying load resistances for a frequency range of 20 Hz to 100 Hz, in steps of 20 Hz. The results demonstrated that the maximum power generated was 8.41 μW at a load resistance of 100 kΩ and frequency of 100 Hz. This relates to a power density of 639.6 μW/cm3 for the fabricated magneto-electric energy harvester.

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.

A piezoelectric based vibration energy harvester fabricated using screen printing technique

A d3i mode piezoelectric based vibration energy harvester (PVEH) has been successfully fabricated using screen printing technique for wireless micro sensor network applications. Polyvinylidene fluoride (PVDF), as a piezoelectric layer, was screen printed onto a glass substrate. The cured screen printed PVDF film was peeled off from the glass substrate and polarized by applying 10 kV across its layer. The polarized PVDF layer was sandwiched between two Metglas conductive electrodes, to form a d31 mode unimorph cantilever beam structure. The fabricated PVEH device was mechanically excited at its first resonance frequency (54 Hz) using base shaking experiments. The experimental results demonstrated that the developed energy harvester generated a maximum DC voltage of 1.35 V across a 10 Mfi load and a peak power output of 0.28 μW was delivered to a 1 MΩ resistive load at 0.53 V DC for a sinusoidal vibration of 15 g. The corresponding power density of the device was calculated to be 11.67 μW/cm3.