Ileana Manunza

Flexible, organic, ion-sensitive field-effect transistor

Organic ion-sensitive field-effect transistors assembled on flexible plastic films have been fabricated. A thin Mylar™ foil acts both as substrate and gate dielectric. The active layer is vacuum-sublimed on one side of the foil, prepatterned with bottom-contact Au source and drain electrodes. The opposite side of the insulating film is in contact with an electrolytic solution that together with a reference electrode forms an ionic gate. A sensitivity of the device to the pH of the electrolyte solution has been observed. Thanks to the flexibility of the substrate and the low cost of the employed technology, this device opens the way for flexible sensors that can be employed in a variety of innovative applications.

Tetracene light-emitting transistors on flexible plastic substrates

We report on organic light-emitting (field-effect) transistors (LETs) fabricated on a flexible and transparent plastic foil (Mylar), acting both as substrate and gate dielectric. The foil is patterned on one side with bottom-contact gold source and drain electrodes, while a thin film of gold is evaporated on the opposite side of the foil to form the gate electrode. A vacuum sublimed tetracene film is employed as an active layer for charge transport and light emission. Atomic force microscopy shows that tetracene films have a good adhesion on Mylar and exhibit a granular structure. The transistor shows unipolar p-type behavior with mobilities typically of 5×10−4cm2∕Vs. Drain-source current and electroluminescence have been simultaneously measured. Provided a suitable gate bias is applied, light emission occurs at drain-source voltages (Vds) above saturation. LETs on plastic substrates could open the way to flexible devices combining the switching function of a transistor and the light emission.

Pressure sensing by flexible, organic, field effect transistors

A mechanical sensor based on a pentacene field effect transistor has been fabricated. The pressure dependence of the output current has been investigated by applying a mechanical stimulus by means of a pressurized air flow. Experimental results show a reversible current dependence on pressure. Data analysis suggests that variations of threshold voltage, mobility and contact resistance are responsible for current variations. Thanks to the flexibility of the substrate and the low cost of the technology, this device opens the way for flexible mechanical sensors that can be used in a variety of innovative applications such as e-textiles and robotic interfaces.

Producing Smart Sensing Films by Means of Organic Field Effect Transistors

We have fabricated the first example of totally flexible field effect device for chemical detection based on an organic field effect transistor (OFET) made by pentacene films grown on flexible plastic structures. The ion sensitivity is achieved by employing a thin Mylar foil as gate dielectric. A sensitivity of the device to the pH of the electrolyte solution has been observed A similar structure can be used also for detecting mechanical deformations on flexible surfaces. Thanks to the flexibility of the substrate and the low cost of the employed technology, these devices open the way for the production of flexible chemical and strain gauge sensors that can be employed in a variety of innovative applications such as wearable electronics, e-textiles, new man-machine interfaces

Organic semiconductor field effect transistors for unconventional applications: flexible sensors and wearable devices

We have fabricated the first example of totally flexible field effect device for chemical detection based on an organic field effect transistor (OFET) made by pentacene films grown on flexible plastic structures. The ion sensitivity is achieved by employing a thin Mylar foil as gate dielectric. A sensitivity of the device to the pH of the electrolyte solution has been observed. A similar structure can be used also for detecting mechanical deformations on flexible surfaces. Thanks to the flexibility of the substrate and the low cost of the employed technology, these devices open the way for the production of flexible chemical and strain gauge sensors that can be employed in a variety of innovative applications such as wearable electronics, e-textiles, new man-machine interfaces

Organic field-effect based sensors for body parameters monitoring

In this paper we propose totally flexible organic field effect transistors (OFETs) assembled on plastic films as sensors for physiological parameters monitoring. In the first part, mechanical sensors for pressure and bending detection are presented and some biomedical sensing applications are illustrated. A sharp and reversible sensitivity of the output current of the device to an elastic deformation induced by means of a mechanical stimulus on the device channel is observed. In the second part, the possibility of using similar devices for bio- and chemo-detection is described. By exploiting the properties of the basic structure, the device can be combined with any kind of substrate to detect for instance the 3D bending of a flexible surface and/or for detecting pH of sweat. Robot skin and wearable electronics seem to be promising applications for this emerging technology.

TOWARDS THE PLASTIC ISFET: A FLEXIBLE, ORGANIC, ION SENSITIVE FIELD EFFECT TRANSISTOR

We have fabricated the first example of flexible field effect device for chemical detection based on an organic field effect transistor (OFET) made by pentacene films grown on flexible plastic structures. The ion sensitivity is achieved by employing a thin MylarTM foil as gate dielectric. The active layer is vacuum-sublimed on one side of the foil, pre-patterned with bottom-contact Au source and drain electrodes. The opposite side of the insulating film is in contact with an electrolytic solution that together with a reference electrode forms an ionic gate. A sensitivity of the device to the pH of the electrolyte solution has been observed. Thanks to the flexibility of the substrate and the low cost of the employed technology, this device opens the way for the production of flexible chemical sensors that can be employed in a variety of innovative applications.

Organic Field-Effect Based Devices for Pressure Detection

We describe pressure sensors realised starting from completely flexible organic thin film transistors (OTFTs). A flexible and transparent plastic foil (Mylar) is employed both as substrate and gate dielectric; gold source and drain electrodes are patterned on the upper side of the foil while the gate electrode lies on the opposite side; a vacuum-sublimed pentacene film acts as active layer. The pressure dependence of the output current has been investigated by applying to the gate side of the device a mechanical stimulus by means of a pressurized air flow. Experimental results show a reversible current dependence on pressure; further data analysis suggests that current variations are due to pressure-induced variations of mobility and threshold voltage.

An organic thin film transistor structure for optoelectronic applications

In this work we present an innovative structure for organic Thin Film Transistors (TFTs) that is transparent, flexible, and optimized for a good behaviour at relatively high frequencies. Starting from a basic structure, several possible options for building such kind of structure can be implemented. In this work, material, technology, and measurement issues will be discussed.