A novel capacitive pressure sensor based on micro-structured polydimethylsiloxane (PDMS) dielectric layer was developed for wearable E-skin and touch sensing applications. The pressure sensor was fabricated on a flexible polyethylene terephthalate (PET) substrate, using PDMS and silver (Ag) as the dielectric and electrode layers, respectively. A set of PDMS films with pyramid shaped micro-structures were fabricated using a laser engraved acrylic mold. The electrodes (top and bottom) were fabricated by depositing Ag on PET films using additive screen-printing process. The pressure sensor was assembled by attaching the top and bottom Ag electrodes to the smooth side of pyramid shaped micro-structured PDMS (PM-PDMS) films. The top PM-PDMS was then placed on the bottom PM-PDMS. The capability of the fabricated pressure sensor was investigated by subjecting the sensor to pressures ranging from 0 to 10 kPa. A sensitivity of 0.221% Pa-1, 0.033% Pa-1 and 0.011% Pa-1 along with a correlation coefficient of 0.9536, 0.9586 and 0.9826 was obtained for the pressure sensor in the pressure range of 0 Pa to 100 Pa, 100 Pa to 1000 Pa, and 1 kPa to 10 kPa, respectively. The pressure sensor also possesses a fast response time of 50 ms, low hysteresis of 0.7%, recovery time of 150 ms and excellent cycling stability over 1000 cycles. The results demonstrated the efficient detection of pressure generated from various activities such as hand gesture and carotid pulse measurement. The PM-PDMS based pressure sensor offers a simple and cost-effective approach to monitor pressure in E-skin applications.

A novel flexible capacitive pressure sensor based on hybrid micro-structured (HM) polydimethylsiloxane (PDMS) dielectric layer was developed. The HM-PDMS with M-tooth structured patterns was fabricated using a laser engraved acrylic master mold. The top and bottom electrodes were fabricated by depositing silver (Ag) on flexible polyethylene terephthalate PET) substrate using additive screen-printing process. The pressure sensor was assembled by sandwiching two HM-PDMS based dielectric layers between the top and bottom electrodes. The capability of the developed pressure sensor to detect a wide range of pressure was investigated by applying varying pressure from 0 to 1 kPa, 1 to 10 kPa, and 10 kPa to 40 kPa. A sensitivity of 51.36% kPa ⁻¹ , 8.37% kPa ⁻¹ , and 2.46% kPa ⁻¹ was obtained for the pressure ranges of 0 to 1 kPa, 1 to 10 kPa, and 10 to 40 kPa, respectively. The capacitive pressure sensor response, hysteresis, and repeatability of the fabricated pressure sensor is investigated and presented in this paper. To demonstrate the wide sensing range of the pressure sensor, the sensor was attached to face mask for breath monitoring applications that require low pressure sensing of ~20 Pa, and to the hand glove for fingertip pressure monitoring applications that require relatively high pressure sensing of ~3 kPa.

Four designs (D1-D4) of flexible triboelectric nanogenerators (TENGs) were successfully fabricated in three different configurations for energy harvesting applications. Typically, TENG consists of anode layer, cathode layer, and electrodes. Combination of materials were investigated in this study using polyethylene terephthalate (PET), thermoplastic polyurethane (TPU) and a flexible fabric as top triboelectric (cathode) layers; Kapton and polydimethylsiloxane (PDMS) as bottom triboelectric (anode) layers. Copper (Cu) tape and screen-printed silver (Ag) were used as electrodes. Each of these designs (D1-D4) has three configurations C1, C2 and C3 in which the top substrate (cathode layer) was different from one configuration to other. In order to determine the best material combination that would provide better TENG performance, different configurations were considered. The capability of the TENGs in terms of open circuit voltage (V _oc ) and short circuit current (I _sc ) were demonstrated by subjecting them to ~5 to 6 N force at 10 Hz operating frequency. A maximum V _oc of 21.61 ± 2.27 V _pp , 35.32 ± 0.89 V _pp , 31.21 ± 1.43 V _pp and 45.75 ± 5.09 V _pp resulted in a power density of 0.29 μW/cm², 1.12 μW/cm², 0.47 μW/cm² and 0.91 μW/cm² from the D1, D2, D3 and D4 designs, respectively. The TENG fabricated using screen printed Ag flake on PDMS and fabric (D4) exhibited the highest open circuit output and a good repeatability after six months of re-testing with a maximum difference of ~ 7.39 % change(ΔV/V) in the output signal. In addition, a cyclic test was performed on D4, the results obtained demonstrate a good durability of the TENG sensor over 1000 cycles. The fabricated TENG device has a simple design, compact size, and demonstrated a better performance in comparison with some of the other works in terms of output voltage.

A flexible anode was developed with graphene nanoplatelet (xGnP) as the anode material for fabricating fast charging lithium-ion battery. The ink consists of graphene nanoplatelets as active material along with C-45 carbon black as conductive additive and polyvinylidene fluoride (PVDF) as binder. The ink was bar coated on to two flexible copper films to form anodes with mass loadings of 2.8 mg/cm ² and 7.2 mg/cm ² . Then the anode was laser patterned to introduce secondary pore network (SPN) consisting of pores with a diameter of ~33 μm and an edge-to-edge distance of ~42 μm between the pores. The mass loadings of laser patterned anodes were measured to be 2.1 mg/cm ² and 5.6 mg/cm ² . Half-cell lithium-ion batteries was assembled with fabricated anodes with lithium metal foil as counter electrode. Ethylene carbonate and dimethyl carbonate (EC: DEC) in 50/50 (v/v) mixed with 1M lithium hexafluorophosphate (LiPF ₆ ) was used as electrolyte in assembled coin-cells. Formation, rate and cycling tests were performed for bar-coated (without SPN) and laser patterned (with SPN) cells with different mass loadings at different C-rates. Cells with SPNs exhibited higher specific capacities of 420 mAh/g, 315 mAh/g and 207 mAh/g at high mass loading, at fast charging C-rates of 2C, 4C and 6C, respectively. Cells with SPNs showed superior capacity retention close to 90% when compared to cells without SPNs (38%) after 200 cycles at 2C-rate. Effect of SPN’s was significantly evident during rate and cycling performance of anodes at high mass loading. This study demonstrated the significance of implementing SPNs in the electrodes for achieving fast charging lithium-ion batteries with high mass loading.

Fabricating electrodes with low tortuosity and fast charging capabilities is pivotal for advancing the field of electric vehicles. A cathode ink was prepared using NMC 811 (LiNi 0.8 Co 0.l Mn 0.l O 2 ) as active material alongside carbon black as conductive additive, polyvinylidene fluoride (PVDF) as binder and n-methyl-2-pyrrolidone (NMP) as solvent. The cathodes were fabricated by bar-coating the ink on an aluminum foil, which acts as a current collector. Laser patterning was performed to introduce structured pore networks (SPNs) into the cathode with a pore diameter of 80 $\mu \mathrm{m}$ and edge-to-edge distance (ETE) of 75 $\mu\mathrm{m}$ between the pores. The significance of the structured electrode was investigated by conducting electrochemical tests on the coin-cells assembled with and without SPNs at high mass loadings of approximately 14 $\text{mg}/\text{cm}^{2}$ . The cathode with SPNs exhibited superior capacity of 134 mAh/g compared to the capacity of control bar-coated electrode (without SPNs) 93 mAh/g at highest C-rate of 6C. The structured electrode also displayed excellent capacity retention of 99% at the end of rate test. The improvement in the performance of cells is due to the reduction in tortuosity resulted from laser patterned SPNs in the cathode.