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A flexible wireless electrocardiogram (ECG) device, integrated with fabric was fabricated for monitoring physiological signals in wearable biomedical applications. The ECG device consists of dry electrodes and a readout module. The dry electrode was fabricated by depositing multi-walled carbon nanotube (MWCNTs)/polydimethylsiloxane (PDMS) composite on a thermoplastic polyurethane (TPU) substrate with screen printed silver (Ag) layer. The readout module with wireless data transmission capability was designed and fabricated on a flexible polyimide substrate. The ECG device was attached to fabric, and its performance was investigated by measuring the ECG signals and comparing them with the results of conventional wet Ag/AgCl electrode. It was observed that the device demonstrated similar performance in terms of signal intensity and correlation when compared to the conventional wet ECG electrodes. Signal-to-noise-ratio (SNR) analysis clearly showed that the dry electrodes with an average SNR of 23.1 dB, perform better than the commercially available Ag/AgCl electrodes (SNR of 21.2 dB). In addition, the capability of the fabric based dry electrodes to measure ECG signals during the physiological activities under exercise motions was studied. This enabled understanding the effect of motion artifacts on the dry electrode response and allowed comparing the obtained ECG signals with the responses of conventional wet ECG electrodes (subjected to similar conditions). It was observed that, even though dry electrodes didn’t use any kind of adhesive gel for measuring the ECG signals, they performed very similar to conventional wet electrodes. The results obtained clearly demonstrated the feasibility of employing fabric based flexible dry ECG electrodes for continuous monitoring of ECG signals in health care applications and can potentially replace the wet electrodes.

Design and rapid prototyping of a tunable and compact microstrip antenna for industrial, scientific and medical (ISM) band applications is presented in this paper. Laser machining is introduced as a fast and accurate method for the antenna fabrication. The antenna, with an overall dimension of $65\times 46\times0.127$ mm, was fabricated by sandwiching a flexible Kapton polyimide substrate, with a dielectric constant of 3.5, between two flexible copper tapes, as the radiating patch and ground plane, respectively. The radiating patch was patterned in a meander configuration, with three slots, demonstrating the capability to reduce the resonant frequency of the microstrip antenna from 2.4 GHz to 900 MHz, without increasing the overall size of the antenna (87% compact). The effect of mechanical stress on the antenna performance was investigated by performing bend and stretch tests. The antenna was subjected to compressive bend with a minimum radius of curvature of 86 mm and 150 mm along the x-axis and y-axis which resulted in a maximum increase of resonant frequency by 3.1% and 1.3%, respectively. Similarly, the antenna was subjected to tensile bend with a minimum radius of curvature of 79 mm and 162 mm along the x-axis and y-axis which resulted in a maximum decrease of the resonant frequency by 4.2% and 0.3%, respectively. An overall 0.9% decrease in the resonant frequency was measured for an applied strain of 0.09% during stretching the antenna along the y-axis.

This paper is focused on the development of a flexible and portable electrochemical system that can be used with a variety of two and three-electrode sensors while maintaining tremendous accuracy. Both the two-electrode and three-electrode sensors were created from a copper sheet using a laser etching process. The fabricated sensor was connected to a printed circuit board that was custom designed to measure the sensor response using different electrochemical techniques such as cyclic voltammogram as well as chronoamperogram towards varying concentrations of analytes. Once the sensor is calibrated, the system was able to detect the chemical concentrations and transmit the results wirelessly through Bluetooth. The system is powered with a 3.7V rechargeable lithium polymer battery which pulls ~2.8 mA resulting in a very low power consumption. Post analysis was performed on the custom smartphone application to view the analyte concentrations and record the results.

This paper is focused on the design and fabrication of a fully functional handheld and portable electrochemical analyzer for flexible hybrid electronics applications. A three-electrode sensor was fabricated from copper tape using laser etching process. The sensor was connected to a custom designed and programmed printed circuit board to measure the sensor response through electrochemical techniques for a large variation of chemical ion concentrations. The electronic circuit can perform cyclic voltammogram and chronoamperogram tests. After calibration, the measurements can be wirelessly transmitted to a smartphone and enables the user to view post analysis results including the analyte concentrations. The system is power efficient running off a 3.7V lithium polymer battery pulling ~2.8 mA.

A novel porous polydimethylsiloxane (PDMS)-based capacitive pressure sensor was fabricated by optimizing the dielectric layer porosity for wide-range pressure sensing applications in the sports field. The pressure sensor consists of a porous PDMS dielectric layer and two fabric-based conductive electrodes. The porous PDMS dielectric layer was fabricated by introducing nitric acid (HNO3) into a mixture of PDMS and sodium hydrogen bicarbonate (NaHCO3) to facilitate the liberation of carbon dioxide (CO2) gas, which induces the creation of porous microstructures within the PDMS dielectric layer. Nine different pressure sensors (PS1, PS2,..., PS9) were fabricated in which the porosity (pore size, thickness) and dielectric constant of the PDMS dielectric layers were varied by changing the curing temperature, the mixing proportions of the HNO3/PDMS concentration, and the PDMS mixing ratio. The response of the fabricated pressure sensors was investigated for the applied pressures ranging from 0 to 1000 kPa. A relative capacitance change of ∼100, ∼323, and ∼485% was obtained by increasing the curing temperature from 110 to 140 to 170 °C, respectively. Similarly, a relative capacitance change of ∼170, ∼282, and ∼323% was obtained by increasing the HNO3/PDMS concentration from 10 to 15 to 20%, respectively. In addition, a relative capacitance change of ∼94, ∼323, and ∼460% was obtained by increasing the PDMS elastomer base/curing agent ratio from 5:1 to 10:1 to 15:1, respectively. PS9 exhibited the highest sensitivity over a wide pressure sensing range (low-pressure ranges (

A flexible wireless electrocardiogram (ECG) device was fabricated for monitoring physiological signals in wearable biomedical applications. The ECG device consists of dry electrodes and a readout module. The dry electrode was fabricated by depositing multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composite on a thermoplastic polyurethane (TPU) substrate with screen printed silver (Ag) layer. The readout module with wireless data transmission capability was designed and fabricated on a flexible polyimide substrate. The ECG device was attached to a fabric, and its performance was investigated by measuring the ECG signals and comparing the signals with the results of conventional wet Ag/AgCl ECG electrode ECG signals. It was observed that the device demonstrated equal performance in terms of signal intensity and correlation when compared to the conventional wet ECG electrodes. The methodology and results of the device are analyzed and presented in this paper.

A fabric based porous polydimethylsiloxane (PDMS) pressure sensor was developed and the effect of curing temperature on the porosity as well as the sensitivity was investigated. Three different porous PDMS dielectric layers (D1, D2 and D3) were prepared by curing a mixture of PDMS, sodium hydrogen bicarbonate (NaHCO 3 ), and nitric acid (HNO 3 ) at 110 $^{\circ}C$, 140$^{\circ}C$ and 170$^{\circ}C$, respectively. The top and bottom electrodes of the pressure sensor were fabricated by screen printing silver (Ag) on a thermoplastic polyurethane (TPU) film. The screen-printed Ag-TPU film was permanently attached to a fabric using heat lamination process. Three pressure sensors, PS1, PS2 and PS3 were assembled by sandwiching the porous dielectric layers D1, D2 and D3 between the top and bottom electrodes, respectively. An average pore size of $411 \mu \mathrm{m}, 496 \mu \mathrm{m}$, and $502 \mu \mathrm{m}$ was measured for D1, D2 and D3, respectively. A relative capacitance change of $\sim 100$%, $\sim$ 323%, and $\sim$ 485% was obtained for the pressure sensors PS1, PS2, PS3, respectively, for varying applied pressures ranging from 0 to 1000 kPa. The effect of curing temperatures on the thickness as well as the dielectric constant of the porous PDMS layer, which in turn changes the sensitivity of the pressure sensors, was investigated and is presented in this paper.

A novel porous polydimethylsiloxane (PDMS) capacitive pressure sensor was fabricated on a fabric platform using additive screen printing process. The porous PDMS was prepared using a mixture of PDMS, sodium hydrogen bicarbonate (NaHCO3) and nitric acid (HNO3) and implemented as a dielectric layer. The fabric based top and bottom electrodes were developed by screen printing silver (Ag) ink on thermoplastic polyurethane (TPU) and permanently attaching it on to a fabric using heat lamination process. The capacitive response of the pressure sensor was recorded for varying pressures ranging from 0 to 900 kPa. A relative capacitance change of ~10%, ~180% and ~300% was obtained for the applied pressure ranges of 0 to 20 kPa, 50 to 200 kPa and 300 to 900 kPa, respectively. The detailed fabrication process of the pressure sensor as well as its capacitive response is analyzed and reported in this paper.

In this paper, we present the design and implementation of a smart strain based sensory glove for remote control (RC) car applications. This glove would control the RC car with individual finger movements. Laser carbonization was implemented as a fabrication method for developing strain sensors which were integrated on a Polydimethylsiloxane (PDMS) platform. Various sensor designs were fabricated and tested to determine the effectiveness of the glove design. This laser carbonization method resulted in a directional anisotropic characteristic with a relative resistance change of 170× when bent from an angle of 0 ° to 145 ° (complete finger bend).

A novel fluorinated graphene-based humidity sensor was successfully developed for humidity monitoring applications. The humidity sensor was fabricated by screen printing silver (Ag) interdigitated electrodes (IDEs) on a flexible polyimide substrate. A fluorinated graphene powder, that was uniformly dispersed in isopropyl alcohol (IPA) using the ultra-sonication process, was drop casted on the IDEs as a humidity sensing layer. The resistive response of the fabricated humidity sensor towards varying relative humidity (RH) levels ranging from 20% RH to 70% RH, in steps of 10% RH, was investigated at a constant temperature of 24 °C. A maximum resistance change of 12.1% was observed when the humidity was changed from 20% RH to 70% RH, with a sensitivity of 0.24 %/%RH.

Design and rapid prototyping of a tunable and compact microstrip antenna for industrial, scientific and medical (ISM) band applications is presented in this paper. Laser machining is introduced as a fast and accurate method for the antenna fabrication. The antenna, with an overall dimension of 65×46×0.125 mm, was fabricated by sandwiching a flexible Kapton polyimide substrate, with a dielectric constant of 3.5, between two flexible copper tapes, as the radiative patch and ground plane, respectively. The radiative patch was patterned in a meander configuration, with three slots, demonstrating the capability to reduce the resonant frequency of the microstrip antenna from 2.4 GHz to 900 MHz, without increasing the overall dimension of the antenna. Copper tape, with a thickness of 0.03 mm was selected, not only for its ease of use but also for its flexibility in tuning the antenna response to achieve the exact simulated results during the antenna experiment and eliminating the unavoidable differences between simulation and measurement outputs.

A resistive flexible humidity sensor based on carbon nanotubes (CNT) was designed and fabricated. Screen and gravure printing processes were used for the fabrication of the humidity sensor containing interdigitated electrodes (IDE), a sensing layer and a meandering conductive heater. The capability of the printed sensor was investigated by subjecting it to relative humidity (RH) ranging from 30% to 60%. This response demonstrated an overall resistance change of ~29% when the sensor was subjected to 60% RH, when compared to 30% RH. A maximum hysteresis of ~5.8%, at 40% RH, was calculated for the resistive response of the sensor. The fabrication method and sensor response are analysed and presented in this paper.