Olivier De Sagazan

Conformal Electronics Wrapped Around Daily Life Objects Using an Original Method: Water Transfer Printing

The water transfer printing method is used to transfer patterned films on random three-dimensional objects. This industrially viable technology has been demonstrated to intimately wrap metallic and polymeric films around different materials. This method avoids the use of rigid substrate during the transfer step. Patterns can be transferred to objects without folds even when holed, addressing a challenging issue in the field of conformal electronics. This technique allows high film bending properties to be reached. This promising method enables us to integrate large-area films onto daily life objects. A bent capacitive touchpad is fabricated showing the potential applications of this technology.

Highly Flexible Microcrystalline Silicon n-Type TFT on PEN Bent to a Curvature Radius of 0.75 mm

Electrical and mechanical performances of microcrystalline silicon top-gate thin-film transistors (TFTs) on flexible substrate under high bending is presented. These devices are directly fabricated on 25-μm-thick Polyethylene naphthalate (PEN) at a maximum temperature of 180 °C. Tensile and compressive bending are performed and revealed that the TFTs can hold curvature radii of 1.5 mm without losing their performance and 0.75 mm with lower electrical performances. The limiting factor on the flexibility is shown to be the mechanical behavior of silicon nitride film used as a gate insulator. These extremely high curvatures demonstrate the possibility to use silicon technology in foldable electronics. TFTs are also shown to fully recover their characteristics when reflattened after such very low curvature radii. It opens the way to fold in half an electronic circuit to be stored and reused when reflattened.

Contactless Microstrip Transition for Flexible Microfluidic Circuits and Antennas

This letter presents an ultrawideband contactless microstrip-to-microstrip transition connecting a conventional surface line with an embedded microfluidic line composed of a room-temperature liquid metal. The operational bandwidth of the transition spreads from about 0.8 to 7.9 GHz, which corresponds to the fractional bandwidth of ~ 165%. A detailed parametric study is reported for the transition geometrical parameters and substrate curvature. The performance of the transition is validated successfully via prototyping. The liquid metal used is galinstan, and the substrate is made of PDMS.

MOSFET on Thin Si Diaphragm as Pressure Sensor

This paper presents original designs of pressure sensor combining thin membrane micro-technology with a simple MOSFET (Metal Oxide Silicon Field Effect Transistor) detection. The proposed microelectronic process (fig. 1) is quite simple and could lead to the development of low pressure sensor. The sensor designs are based on square and cross shaped P-channel MOSFET directly integrated on the diaphragm. Electrical characterization of the FET-sensor shows wide drift of the characteristics in response to mechanical strain on the membrane. The shift importance is shown to depend on the different designs used to fabricate the FET-sensors.

pH meter based in Suspended Gate Field Effect Transistors to application in monitoring of water quality

The protocol to monitor the water pH variation during a long time using a full electronic pH-meter consisting of a SGFET (Suspended Gate Field Effect Transistor) is presented after the analysis of the transconductance and the drain current drifts under pH. The main advantages of using this device are its high sensitivity and the ability to integrate it with the electronic treatment into a miniaturized system.

Direct Electrical Detection of Biological Species

Suspended-Gate FETs, namely SGFET, with sub-micron gap, is shown to be able to detect biological species with very high sensitivity in a large range of concentration. Examples of detection of DNA (through the DelF508 mutation of the cystic fibrosis gene that is widely disseminating in Europe and North America, and one mutation of BRCA1 gene that is the main indication of the possibility for a woman to have breast cancer) and proteins (through the transferrin that is the only carrier of iron in blood) are presented. This very sensitive electrical detection without any labelling is shown to deliver directly readable signal.

(Invited) Dual-Gate TFT for Chemical Detection

Electronic devices have shown their interests to develop chemical and biological sensors based on electrical detection. Various field effect transistor structures applied to those detections exist and can be used in liquids, but have often a limited sensitivity, especially due to the Nernst limit. Dual gate field effect transistor allows to enhance this sensitivity by capacitive amplification. This paper describes the development of a field effect transistor based on polycrystalline silicon. Technological parameters as thicknesses and doping level are studied in order to obtain a good amplification. Polarization conditions are optimized in order to fit the requirements for testing in liquid media. The specific use of polycrystalline silicon as active layer can lead to a high amplification of charges and/or potential levels. A proof of sensing detection is obtain with pH measurement.

Humidity Sensor Thanks Array of Suspended Gate Field Effect Transistor

This work deals with a sensor using array of Suspended Gate Field Effect Transistor (SGFET) to measure the relative humidity (%RH). Technics of microtechnology are used to fabricate a polysilicon bridge with a gap de 0,5 μm which acts as transistor gate. Electrical measures have been realized by sampling mode, involving a sensitivity of -5 μA/%. Also the SGFET humidity sensors are very interesting due to the simplicity to polarize and to analyze the output signal.