We have developed and demonstrated a highly flexible P(VDF-TrFE) film-based energy harvesting device on a PDMS substrate, avoiding any complex composites and patterned structures. The structural and electrical properties of the P(VDF-TrFE) film was investigated using multiple characterization techniques and an optimized film of 7 µm thickness was used for the energy harvesting application. The device, with Ti/Ni metal contacts, was driven by a shaker providing an acceleration of 1.75 g, and frequencies varying from 5 to 30 Hz. The energy harvesting performance of the final fabricated device was tested using the shaker, and resulted in a maximum output capacitor voltage of 4.4 V, which successfully powered a set of 27 LEDs after several minutes of charging.

A reverse bias tunable Pd- and Pt-functionalized graphene/Si heterostructure Schottky diode H2 sensor has been demonstrated. Compared to the graphene chemiresistor sensor, the chemi-diode sensor offers more than one order of magnitude higher sensitivity as the molecular adsorption induced Schottky barrier height change causes the heterojunction current to vary exponentially in reverse bias. The reverse bias operation also enables low power consumption, as well as modulation of the atomically thin graphene's Fermi level, leading to tunable sensitivity and detection of H₂ down to the sub-ppm range.

A highly sensitive Gallium Nitride (GaN) diaphragm based micro-scale pressure sensor with an AlGaN/GaN heterostructure field effect transistor (HFET) deflection transducer has been designed and fabricated for high temperature applications. The performance of the pressure sensor was studied over a pressure range of 20 kPa, which resulted in an ultra-high sensitivity of ~0.76%/kPa, with a signal-to-noise ratio as high as 16 dB, when biased optimally in the subthreshold region. A high gauge factor of 260 was determined from strain distribution in the sensor membrane obtained from finite element simulations. A repeatable sensor performance was observed over multiple pressure cycles up to a temperature of 200 °C.

Self-polarized energy harvesting materials have seen increasing research interest in recent years owing to their simple fabrication method and versatile application potential. In this study, we systematically investigated self-polarized P(VDF-TrFE)/carbon black (CB) composite thin films synthesized on flexible substrates, with the CB content varying from 0 to 0.6 wt.% in P(VDF-TrFE). The presence of –OH functional groups on carbon black significantly enhances its crystallinity, dipolar orientation, and piezoelectric performance. Multiple characterization techniques were used to investigate the crystalline quality, chemical structure, and morphology of the composite P(VDF-TrFE)/CB films, which indicated no significant changes in these parameters. However, some increase in surface roughness was observed when the CB content increased. With the application of an external force, the piezoelectrically generated voltage was found to systematically increase with higher CB content, reaching a maximum value at 0.6 wt.%, after which the sample exhibited low resistance. The piezoelectric voltage produced by the unpoled 0.6 wt.% CB composite film significantly exceeded the unpoled pure P(VDF-TrFE) film when subjected to the same applied strain. Furthermore, it exhibited exceptional stability in the piezoelectric voltage over time, exceeding the output voltage of the poled pure P(VDF-TrFE) film. Notably, P(VDF_TrFE)/CB composite-based devices can be used in energy harvesting and piezoelectric strain sensing to monitor human motions, which has the potential to positively impact the field of smart wearable devices.

A graphene-based ISFET has been developed and demonstrated high sensitivity and direct measurement of K ⁺ ion efflux from live cells.

The effect of epoxy exposure and its curing agent (trimethyl-1, 6-hexanediamine), widely used for the biocompatible packaging of graphene-based devices, on the electrical characteristics of a graphene field effect transistor is investigated in this work. Upon 5 min of the epoxy curing agent exposure, the Dirac point shifted from 60 to 13 V, while for 15 min of the epoxy curing agent exposure, the Dirac point changed more than 130 V, from 63 to −68 V, completely changing the doping of graphene from strong p-type to strong n-type due to the electron donating nature of the adsorbed molecules. Additionally, due to exposure, the hole mobility was found to reduce from 1243 to 401 cm² V⁻¹ s⁻¹, indicating the strong impact of ionized impurity scattering. The temperature-dependent Hall measurement of single layer graphene before and after the epoxy curing agent exposure also exhibited a change in the dominant scattering mechanism from surface optical phonon scattering to Coulomb scattering near room temperature due to epoxy exposure. Reduction of initial p-type doping in chemical vapor deposited (CVD) graphene after epoxy exposure is also confirmed by Raman spectroscopy. We found that the Dirac point recovered very slowly upon storage of the epoxy (or curing agent) exposed devices, changing by only ~11 V after 4 months without significant change in carrier mobility.