Combination of CP and CSA WP8 Flexible Electronics ... D8.5Fully-flexible... · scope of the...

Project funded by the European Commission under grant agreement n°604391

GRAPHENE Graphene-Based Revolutions in ICT and Beyond

Combination of CP and CSA

WP8 Flexible Electronics

Deliverable 8.5 “Fully flexible electronic device which combines several key technology enablers for flexible electronics”

Main Author(s): Samiul Haque, Darryl Cotton, Adam Robinson, Salvatore Zarra, Matteo Bruna, Stefano Borini (Nokia

R&D UK), Salvatore Abbisso, Santo Smerzi, Sebastiano Ravesi (ST), Sanna Arpiainen, Vladimir

Ermolov, Henrik Sandberg (VTT), Emanuele Treossi, Alessandra Scida’, Vincenzo Palermo (CNR),

Jamal Tallal, Etienne Quesnel (CEA), Andrea C. Ferrari, Felice Torrisi, Lucia Lombardi, Panagiotis

Karagiannidis (UCAM), Heiner Friedrich (TUE), Christoph Stangl (VMI), Aldo Di Carlo (UTV), Mark

Spratt, John Meschter (G24), Francesco Bonaccorso (IIT)

Due date of deliverable: M30

Actual submission date: M30

Dissemination level: PU

GRAPHENE D8.5 15 March 2016 2 / 15

LIST OF CONTRIBUTORS

Partner Acronym Partner Name Name of the contact

2 CNR Consiglio Nazionale delle Ricerche Vincenzo Palermo

11 CEA Commissariat à l’énergie atomique

et aux énergies alternatives

Jamal Tallal

23 STM STMicroelectronics Sebastiano Ravesi

24 VTT VTT Henrik Sandberg

25 VMI Varta MicroInnovation Christoph Stangl

26 GRAPHENEA Graphenea Amaia Zurutuza

28 UCAM The Chancellor, Masters and

Scholars of the University of

Cambridge

Andrea C. Ferrari

38 IIT Fondazione Istituto Italiano di

Tecnologia

Francesco Bonaccorso

77 NOKIA.UKL Nokia R&D UK Ltd. Samiul Haque

102 TUE Technical University Eindhoven Heiner Friedrich

105 Tor Vergata Università degli Studi di Roma "Tor

Vergata"

Aldo Di Carlo

107 G24 G24 Power Ltd Mark Spratt


TABLE OF CONTENTS Deliverable Summary ...........................................................................................................................4 Flexible electronic system including several graphene-based flexible components ...............................5

System design and architecture .......................................................................................................5 System assembly.............................................................................................................................7

Fully flexible wearable device including graphene-based enabling technologies ...................................8 System design and architecture .......................................................................................................8 Manufacturing and assembly ...........................................................................................................8 Demonstration of system functionality ............................................................................................ 11

Flexible wireless demonstrators ......................................................................................................... 11 Flexible NFC tag ............................................................................................................................ 11 Other flexible wireless tags/antennas ............................................................................................. 13

Flexible biosensor system .................................................................................................................. 14 Conclusions ....................................................................................................................................... 15


Deliverable Summary

The objective of this deliverable is the demonstration of a flexible electronic device enabled by various

graphene-based technologies combined together into a system.

This has been achieved in two ways:

• In a first demonstrator, several graphene-based flexible components – including sensors,

batteries, and PV cells - have been combined together into a functional flexible electronic

system, using flexible connectors to integrate the components with standard Si-based

electronics.

The flexible electronic system has been tested and its functionality successfully demonstrated.

• In a second demonstrator, a fully flexible wearable device – based on graphene sensors and

conductive interconnects – has been realised, in order to illustrate a possible application field

enabled by graphene technology. Such a demonstrator represents a first step towards a

seamless integration of graphene components into flexible modules, which shall be in the

scope of the flexible electronics related activity within the Core1 project.

The second demonstrator is a hand worn flexible device, featuring infrared sensors (positioned at the

fingertips) and strain gauge sensors (monitoring the fingers position) both based on graphene. The

sensors are interconnected by graphene conductive tracks, and LEDs are used as a wearable user

interface.

In addition to these prototypes, graphene flexible antennas have also been realised and demonstrated

at a system level: for example, a graphene NFC tag has been realised and read out by a smartphone,

and printed UHF tags have been demonstrated with commercially available readers. This illustrates

the potential of graphene technology as an enabler for flexible wireless devices.

Finally, a flexible system based on the graphene FET technology has been demonstrated. A flexible

graphene solution-gated FET-type biosensor has been realised, with a Point-of-Care (PoC) reader

sized Programmable System on Chip (PSoC) connected to a laptop, showing the promise of graphene

as a PoC sensor platform for quantitative electrical biosensing.

The latter device-level demonstrators could potentially be easily integrated as additional modules

within the flexible electronic platform (demo above), and several other device-level demonstrators

have been produced in the Work Package and are reported elsewhere.


Flexible electronic system including several graphene-based flexible components A flexible electronic system has been realised, including the following graphene-based components

(see description of selected components in the deliverable report D8.3 at M24):

• IR sensor (Temperature sensor) (NOKIA)

• Strain Gauge sensor (UCAM and VTT)

• Flexible battery (VMI)

A flexible graphene-based PV module has been realised by WP9 partners (UTV in collaboration with

G24 and IIT) and integrated within the platform. The PV module is based on the Dye Solar Cell

photovoltaic technology that shows superior performance with indoor lightening with respect to

conventional silicon PV. The module has been realised by using Graphene catalysts on the top

electrode of the module. Graphene has been spray coated onto a PET-ITO flexible substrate

These components cooperate in order to define an electronic platform to monitor physical and

environmental parameters as force (strain gauge sensor) and temperature (IR sensor).

System design and architecture

Figure 1: Electronic Platform – System Architecture

An electronic platform has been developed, based on the architecture shown in Figure1. Design and

layout of the printed circuit board (PCB) where the Si-based ICs are assembled have been realised by

CADENCE tools (Orcad Capture and PCB Editor). The electronic platform is able to manage up to

three different graphene based sensors. The analogue signals (related to the environmental

conditions) provided by graphene-based sensors, are digitised by analogue to digital converters, and

sent through the I2C bus to the STM8 microcontroller. This latest manage a wireless communication by

means of a radio (ML24LR) in Near Field Communication protocol (NFC). The transferred data are

visualised by a dedicated Graphical User Interface (GUI). PV module and flexible battery realise the

energy management for the electronic platform where the energetic part of the system is regulated by

an SPV1050 silicon IC (made by STMicroelectronics).

The schematic of the support PCB is structured in different pages (Figure 2).


Figure 2: Support PCB – Electronic Design

Starting from the design, the board layout has been realised (Figure 3).

Figure 3: Support PCB – Layout 3D

A dedicated software allows showing the environmental and physical parameter caught by sensors

directly on a monitor in real time (Figure 4).

Figure 4: Support PCB – Software interface

When the “Start Detection” is ticked, the reader starts the seeking of a tag. If a tag is detected, the

LED, which indicates the “Tag detection”, becomes green and the ID code of the radio is shown in the


“Device detection code”. Pushing the “Start" button the information about temperature and bending are

shown in the dedicated boxes.

System assembly

The sensors foils are connected to the electronic platform using flexible connectors (FPC – Flexible

Printed Circuits) and classical ZIF connectors (Figure 5).

Figure 5: Flexible connector

The contact between the flexible connector and the sensor foils is assured using Anisotropic

Conductive Films (ACF). The ACF consists of metallic particles in an insulating matrix. When the FPC

is pressed at high temperature against the ACF, an electrical path will be created by the metallic

particles allowing a good electrical contact between the FPC and the sensor. Classical ZIF connectors

assure the electrical link between the electronic platform and the sensors foils + FPC system.

Figure 6 shows an example of ACF thermal bonding of FPC with graphene-based biosensor (figure

6-a) and graphene-based infra-red sensor (figure 6-b).

Figure 6: Examples of thermally bonded sensors: G-FET biosensor (left); printed IR sensor (right)

Figure 7: Electronic platform – System assembled

To the ZIF connector

To the flexible sensor

(a) (b)


Fully flexible wearable device including graphene-based enabling technologies A hand-worn flexible device has been realised, based on graphene materials and printed electronics

manufacturing methods.

System design and architecture

Figure 8 Left: Mechanical Design of the assembly for the fully flexible demo. Right: Final Demonstrator

integrated with IR and Strain Sensors, Graphene Interconnects and LEDs for feedback from the

sensors with associated electronics board.

Manufacturing and assembly

Mechanical Design: A two fingered flexible device was designed to showcase the panoply of functional

inks developed within the project. The design was formulated around a 125µm thick planar A4 sheet of

Polyethylene Napthalate (PEN) substrate, selected for its compatibility with the functional inks and the

range of printing and spray coating equipment available to fabricate the device across the different

sites. The PEN substrate is also utilised as the structural frame of the device acting as an anchor point

for 3D printed strap components, feedback LEDs from each sensor and the connection to the external

electronics. The device is designed to be printed on a planar sheet and subsequently cut out for

assembly. During assembly the rGO temperature sensor is folded around the finger and held in place

by a 3D printed buckle therefore demonstrating the sensors compatibility with flex to install

applications.

The demonstrator can be adjusted to fit a range of adults hand sizes to enable multiple users to test

the device. During fabrication of the device, the graphene-based resistive strain gauges align with the

proximal interphalangeal joints of the first and second digit of the hand, allowing the extension flexion

movements of these digits to be monitored. The high gauge factor of the strain gauges enable the low

strains on the surface of the PEN substrate to be easily detected. Conversely, the low strain sensitivity

of the graphene conductors allow them to be printed on the same plane as the strain gauges without


interfering with the strain gauge or IR sensor signals. Finally, the conductors and strain gauges are

encapsulated with a printed dielectric to prevent damage though light scratches.

Assembly fabrication and printing process: Graphene based inks have been developed within the

consortium during this project. The processing parameters and the screen parameters have been

selected to achieve a combination of sufficient electrical conductivity and spatial definition of the

material. A particular requirement for this demonstrator is the sequential compatibility of processes and

materials. After the initial ink-jet deposition of strain sensor material no further conditioning of the

substrate is possible as that would affect the sensitive sensor material. Therefore it is a great

advantage to be able to apply only graphene based active materials but in quite different formulation.

Electrical leads to the sensors were printed at VTT with the TUE ink. In order to reach the desired form

factor of the demonstrator the flexible integrated device is cut out into the glove shape before

attachment to the external electronics. This cut-out is performed using a programmable laser cutter.

The connecting flat cable and the electronics unit are manufactured separately as well as the plastic

buckles that are 3D printed. The flexible unit is then assembled by additive solution based processes

onto a thin sheet of plastic. First, a strain sensor material (see details below) is deposited by ink-jet

printing onto the bare substrate together with positioning marks in the corners of the area covered by

the full pattern, then electrical leads are deposited by screen printing of graphene based paste in two

steps, first long connection lines which are wider (1 mm) to minimize the electrical resistance, and then

thinner lines where a finer pitch is required closer to the connector. Then a clear encapsulant (Dupont

7165) is added by screen printing to cover the leads and the strain sensor area for protection.

Connector pads for further processing are left uncoated. Next, the device is completed by hybrid

integration of LEDs, connector and the plastic buckles. Finally, the temperature sensor is added by

spray coating or drop casting of a graphene based formulation onto the bare finger electrodes at the far

end of the device. Coarse patterning is achieved by applying a mask.

Figure 9: Printed architecture of the demo showing the various sensors and LEDs mounted on the

flexible substrate.

IR Sensors

FPC Flat Cable

with soldered ZIF

connector


Flexible Sensors on the wearable device: Strain Sensor: UCAM developed a graphene based ink to inkjet print strain sensors on PEN plastics

foils. The use of low boiling point solvent as ethanol was required to inkjet print the graphene ink onto

the non-porous PEN substrates to dry the ink quickly after the jetting of the ink droplets.

Mildly functionalised graphene powder was dispersed in pure ethanol using bath sonication.

Centrifugation steps were then used to purify the produced ink and remove the aggregates.

Each strain gauge consists in 3mmx20mm inkjet printed graphene stripes. 40 printing passes, using

25μm as inter drop distance, were used to decrease the total resistance of each strain sensors. The

strain sensors have a nominal resistance comprised between 100kOhm and 1 MOhm.

The individual strain sensors were used to evidence the functionality of the device. A gauge factor~15

was measured by Nokia showing an advantage with respect to commercial metallic strain sensors. The

figure below shows the testing of the strain sensor on a finger and then on the process substrates

where two strain sensors were printed for the demo.

Figure 10 Left: Printed Strain Sensor tested on the finger for changes in electrical resistance. Right:

Printed Strain sensor on PEN planarised substrate for initial processing of the demo.

Infrared Sensor: The infrared sensor development was carried out by Nokia. The sensing component

employed was a reduced graphene oxide (rGO) film with a reduction level suitable to make it

responsive to incoming infrared radiation. The radiation is absorbed by the rGO sensing material,

heating it and thus changing its electrical resistance (temperature coefficient of resistance of -1.2 %/K,

comparable with a-Si commercial bolometers). An aqueous ink made with this rGO was deposited onto

interdigitated screen printed Ag electrodes on flexible PEN and tested. Its response to mid-infrared

(MIR) radiation was characterised by illuminating the sensor with a source emitting in the wavelength

range 2-14 μm (constant or pulsed light at 2 Hz) and measuring the change in the current (rise time of

250 ms under the conditions employed) passing through at constant voltage.

0 10 20 30 403.03E-006

3.03E-006

3.03E-006

3.03E-006

3.04E-006

3.04E-006

3.04E-006

3.04E-006

3.04E-006

Cur

rent

(A)

Time

SampleB_Step_Sampling50msIntmedium_10mV.csv

10 12 14 16 18 20

3.10E-005

3.11E-005

3.11E-005

3.11E-005

Cur

rent

(A)

Time

SampleB_2HzSampling10msIntmedium_100mV.csv

IR source ON


Figure 11: Response of the IR sensor from a hot source with constant radiation (left) and pulsing at

2Hz (right).

Mechanical and environmental tests were carried on the rGO-based sensor. In particular, its resistance

with varying bend radius (range 6-13 mm) at constant relative humidity and temperature was measured

and compared with the change in resistance due solely to change in temperature, thus concluding that

in the final hand-worn device the bending of the rGO-based sensors will not compromise the detection

of temperature changes due to the incoming infrared radiation of a nearby hot body if these are 5 °C or

higher.

Demonstration of system functionality

Electronics Platform: The wearable device is driven by electronic boards dedicated to acquire the

analogue signals of the sensors (IR and strain gauge) and drive opportunely four LEDs where the

blinking frequency is related to the analogue signals amplitude.

The electronic interface is mainly made up two boards: (i) Analogue board (ii) Digital Board

The design and layout of the Analog Board are below depicted.

Figure 12: Circuit design showing the LED driver and analogue to digital interface. Digital board which

is a commercial evaluation board (STM3221G-EVAL) for the STM32F217 is shown. Connection

assembly for electronics board

Strip line connectors on the Digital board allow interfacing both the analogue signals with the ADCs

inputs and the timer of the microcontroller with the Analog Board. Once connected to the wearable

device when the strain sensors are exploited by moving the fingers the LEDs start to blink with a lower

frequency that can be interchanged with the firmware electronics. As the finger strapped with IR sensor

comes in close proximity (few cm) then the red LEDs start to change frequency. The higher the

temperature the slower or higher the rate of blinking.

Flexible wireless demonstrators

Flexible NFC tag

A graphene based NFC wireless antenna integrated with an ST microelectronics chip has been

demonstrated. The use of highly conductive graphene paper with sheet resistance Rs as low as 0.07

Digital Board


Ω/□ has been investigated and applied to manufacture a highly flexible graphene based NFC wireless

antenna. The antenna showed full compatibility with a commercial reader when flexed at various bend

radii (down to 45 mm) and could also withstand a million bending cycles. The antenna was simulated

and designed to be resonating at 13.56MHz. The antenna was tuned to operate at 13.56 MHz via an

additional parallel capacitor along with the RFID chip control circuit that showed strong resonance and

inductive characteristics after fabrication.

Figure 13: Left: NFC Antenna integrated with Flex FPC Right: Antenna resonance before and after 1

million bending cycles.

Flexible NFC antennas based on graphene nanoplatelets have been prepared by CNR and

Nokia with two different fabrication processes: blade cutting and laser ablation. Several layouts,

materials and configurations were studied and tested in order to maximise the performance. The first

trials were performed by using commercially available products as starting materials, but we then

developed within the Graphene Flagship the capability to produce a graphene paper suitable for the

antennas (collaboration with Nanesa company within WP10). We prepared antennas with conductive

paths characterised by track width of 1-2 mm and gap width until 0,5 mm, with connection of the inner

arm over and below the supporting substrate. In order to obtain a highly flexible antenna with a uniform

mechanical stress along the whole device, several polymeric substrates were tested like PEN, PET,

PVC and Kapton. We explored also the possibility to use graphene for wearable devices realizing a

silk/graphene antenna (fig. 14-4).

Finally, several completely flexible graphene NFC devices were realised by substituting the conductive

path of a ST M24LR NF flexible device with the graphene antenna (fig.14-1).

Different kinds of graphene paper were employed for the preparation of two demonstrators, the first

one with a gap width of 1mm, track width of 2mm and a resistance of 26 ohm, the second one with a

gap of 0.5mm, track width of 2mm and a resistance of 120 ohm. The completely flexible graphene NFC

device demonstrators were tested with a mobile phone through the ST NFC reader App showing good

functionality whether flat or fixed on curved objects (fig. 14-1 and 14-2). Thanks to the ST app is also

possible to program the NFC tag writing a text that can be read after by phone (fig. 14-3).


Figure 14 (1) Graphene NFC Antenna attached on Flexible FPC (2) Antenna bent around a curved

surface (3) Antenna tested with NFC application on Android platform (4) Antenna encapsulated with

silk material for super flexibility

System Testing & Results: A specific testbed has been developed to validate experimentally the

Graphene antennas in a NFC system. For this purpose, two types of FR4 PCBs have been designed

and fabricated: one of them, named antenna PCB, is dedicated to assembly the flexible foil of the

antenna on the PCB rigid substrate and to electrically connect the antenna’s terminals to RF

connectors; the other, named tag PCB, is used to host the ST Microelectronics M24LR device, which is

a NFC passive RF harvester compliant with the ISO 15693 standard. This system has been

successfully powered and interrogated by a commercial NFC reader (the CR96HF reader of ST) and

by NFC-enabled smartphones.

Other flexible wireless tags/antennas

The demo (shown in Fig.15) includes: a reader, a reader antenna and RFID tags. The reader is a

commercial reader Sirit Infinity 510, with an external antenna. The UHF RFID tag consists of a

commercial microchip NXP Ucode G2XM and printed graphene antenna. In the tag prototypes the

microchip is attached using a copper strap that is glued with silver epoxy to the antenna. Tag antennas

were printed of inks developed by TUE on different flexible substrates: kapton, PEM, paper. Testing of

the system shown that at frequency range 865-868 MHz and maximum power of the reader 2 W ERP

reading distance of tags was 4 m. The microchip NXP Ucode G2XM used in the current studies has a

sensitivity of −15 dBm. If state of the art Impinj Monza R6 microchip with a sensitivity of −20 dBm

would be used in combination with the designed antenna, the reading distance would increase up to

7.3 m. The performance of the antenna after 1000 cycles have been tested, does not degrade, and can

be used for verification.


Figure 15 Left: Demo setup including a reader, an antenna of the reader and UHF tags with printed

graphene antennas. Right: Antenna structure design (from VTT) and actual printed antenna with

microchip (graphene ink by TUE).

In addition, two types of flexible UHF antennas were also designed and screen printed by UCAM using

water based graphene inks (DC sheet resistance 5 to 15 Ohm/sq): a meandered design matching the

impedance of the RF Impinj EPC Gen2 Monza4 IC, and the VTT design matching the impedance of

NXP Ucode G2XM microchip.

The read range of the UHF antennas was evaluated by VTT to be 2.5 m using the NXP Ucode G2XM

microchip.

These demonstrators prove that printed flexible graphene antenna can be used in a commercial UHF

RFID system.

Flexible biosensor system A flexible system based on graphene FET technology was also demonstrated. Solution-gated

graphene FET biosensor was fabricated on PET by transferring CVD graphene (VTT, Graphenea) on

prepatterned PET sheet and patterning into devices with UV-lithography (VTT). The devices were

sealed (besides the graphene sensor and reference areas) with Parylene and integrated with flexible

microfluidic channels. These channels do not yet allow capillary fluidics (requires laboratory

dispensers), but for demonstrator purposes, the analysis can also be performed by dispensing a

droplet on the sensor area. The graphene sensor and referencing elements can be contacted from the

side of the sheet with a ZIF connector, allowing interfacing with PSoC4 (Nokia) or with flexible

connector (fig 6.) to the flexible electronic platform. The liquid gate voltage is regulated by graphene

reference electrode, tested to allow as accurate analysis with graphene SGFET as the bulky Ag/AgCl

electrode, and the sensor channel analysis is driven by constant current, both controlled by the PSoC4.

The signal is transferred via USB cable into a laptop, which serves as a user interface, displaying the

analysis results. The sensor operation (Figure 16b,c) was tested after 1000 bending cycles with 15 mm

radius.


Figure 16 a) SGFET biosensor, connectors and control unit (PSoC4) on a green Post-it® sheet during

the measurement. b) Sensor unit with the laptop screen displaying the response to NaP buffer (pH 2,

100 mM) and increasing concentrations of perfluorooctanoic acid (PFOA), shown more precisely in c).

Conclusions

• Graphene materials developed within the work package have been used to successfully

demonstrate several flexible components (sensors, antennas, batteries and signal

interconnects) - all integrated with conventional driving electronics into an electronic system.

• Fully flexible graphene-based electronic systems have been realised, in the form of a hand

worn device and of RFID tags, showing full compatibility with conventional electronics.

• CVD graphene-based flexible biosensor devices have been developed to the level of

robustness allowing sensor readout with handheld electronics, showing potential for the

construction of truly selective quantitative PoC bioanalysis platform.

• The functionality of the flexible systems is shown in videos available at the Graphene Flagship

intranet Onboard

• Good collaboration across WPs (in particular with WP9 and WP10) has contributed to the

successful achievement of the objectives of this Deliverable.

https://onboard.graphene-flagship.eu/wp8/Media%20Library/Forms/Thumbnails.aspx

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