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RESEARCH












RADIOSKIN

Epidermal Electronic Technology for battery-less skin sensors with wireless reading


Abstract


The next wave following the wearable devices (smart watch, and smart bands) is the rise of Epidermal Electronics comprising wireless sensors directly stuck onto the human skin. Radio plasters and tattoos will monitor the personal health and the wellness of people even more tightly and discreetly.

The project RADIOSKIN will provide a substantial advance to the state of the art of epidermal sensors that currently require a battery or a nearly contacting interrogator for data exchange. RADIOSKIN will instead enable a new family of battery-less smart plasters, true “Labs on Skin”, capable to multi-parameter sensing and to be comfortably interrogated from a distance of 1m or more.

Thanks to an already experimented multi-disciplinary synergy (Electromagnetics, Bio-mechanics and Chemical Sensors), RADIOSKIN will face the open challenges of i) the design of devices and antennas placed at a micrometric distance from the human skin and subjected to body deformation, ii) the selection of the most appropriate coating materials for sensing and iii) the hosting membranes suitable to a multi-material inkjet printing technology.

Investigation on models and manufacturing will generate an original knowledge base for the design and demonstration of devices having concrete applicability to the aid to log-term patients and aged users and to the control of epidemic diffusion within base hospitals and airports.

INDEX

TEAM

Expected Results

I. MAIN SCIENTIFIC OUTCOMES
1. Basic Technologies
1.1 Optimal performance of epidermal antennas
1.2 Experimental characterization of biocompatible membranes for epidermal antennas fabrication
1.3 The use of Inkjet Printed Self-Sintering Conductive Ink to fabricate epidermal antennas
1.4 Integration of Skin polymeric flexible batteries onto Skin Antennas
1.5 The use of Graphene-oxide as bio-compatible sensitive nanomaterial onboard skin antennas
2. Proofs of Concepts
2.1 Use of Epidermal Sensors to Restore Peripheral Thermal Feeling
2.2 Clinical Trial at the University of Tor Vergata Hospital of Wireless Epidermal Temperature Sensor in Real Conditions
II. LIST OF PUBLICATIONS
Journals Papers
Conferences Papers
Book Chapters
III. AWARDS
IV. DISSEMINATION



TEAM

Principal investigator
Prof. Gaetano Marrocco, Diaprtimento di Ingegneria Civile ed Ingegneria Informatica, Macro Area di Ingegneria

Research Team (Faculties)
Prof. Corrado Di Natale (University of Roma Tor Vergata)
Prof. Pier Paolo Valentini (University of Roma Tor Vergata)

Master Thesis and PhD Students
Dr. Sara Amendola (University of Roma Tor Vergata)
Eng. Cristina Caccami (University of Roma Tor Vergata)
Eng. Carolina Miozzi (University of Roma Tor Vergata)
Eng. Veronica Di Cecco (University of Roma Tor Vergata)
Eng. Valentina Greco (University of Roma Tor Vergata)
Dr. M. Yussuf Mulla (University of Roma Tor Vergata) 

External Collaborations
Prof. John Batchelor (University of Kent, Canterbury, UK)
Prof. Maria Alfredsson (University of Kent, Canterbury, UK)
Dr. Cecilia Occhiuzzi (Radio6ense srl)
Prof. Gaelle Lissorgues (University of Paris Est, FR)


Expected Results

1) most appropriate layouts for the epidermal antenna in the UHF band and corresponding design guidelines;

2) most appropriate bio-compatible membranes, capable to absorb sweat, for the inkjet-printing procedure and their electromagnetic parameters;

3) most appropriate choice of sensitive materials where the pH strongly impacts on the electric permittivity;

4) proof of concept of the developed technology.



I. MAIN SCIENTIFIC OUTCOMES

1. Basic Technologies







 
1.1 Optimal performance of epidermal antennas

Skin-mounted electronics is the new frontier for unobtrusive body-centric monitoring systems. In designing the wireless devices to be placed in direct contact with the human skin, the presence of the lossy body cannot be ignored because of strong electromagnetic interactions. The performance of epidermal antennas, for application to radio frequency identification (RFID) links in the UHF band, was investigated by means of numerical simulations and laboratory tests on fabricated prototypes. The analysis demonstrated the existence of an optimal size of the antennas (from 3 to 6 cm for loops and from 6 to 15 cm for dipoles) and of upper bounds in the achievable radiation gain (less than −10 dB in the case of 0.5 mm thick application substrates) as a consequence of the balance between the two opposing mechanisms of radiation and loss. This behavior, which is controlled by the hosting medium, does not depend on the antenna shape, but the loop layout permits considerably minimizing the device size. Even the conductivity of the antenna trace plays only a second-order role; low-cost inkjet printable paints with conductivity higher than 104 S/m are suitable to provide radiation performance comparable with the performance of copper-made antennas. Starting from the investigation of the above cited physical phenomena, including the effect of common classes of suitable substrate membranes, guidelines have finally derived for the optimal design of real RFID epidermal antennas.




 


      



1.2 Experimental characterization of biocompatible membranes for epidermal antennas fabrication
Membranes play a crucial role in the manufacturing of epidermal antennas as they represent the interface between the radiators and the human skin. Their mechanical and thermal properties must closely match the skin itself, such to permit an effective adhesion to the skin surface without altering its natural metabolism. From an electromagnetic point side, the presence of thin separating layer helps moreover mitigating the loss of body tissue by concentrating the near field in the low loss region between the antenna and the epidermis. We have focused on the radiofrequency characterization of a set of different wound dressings having potentiality as exudate/sweat sensitive element with the purpose of a forthcoming integration within an RFID epidermal tag. The selected and experimentally characterized membranes involved i) membranes capable of reversibly absorbing/releasing of body fluids, like hydrogels and ii) moisture-retentive dressings undergoing to irreversible transformation after exposure to fluids. The dielectric properties of the selected dressings were measured by a ring resonator device coupled with numerical simulations. The considered materials exhibit different and wide variation range in the UHF band when moving from dry state to the wet condition, which renders them suitable for sensing applications and for being used as the substrates for epidermal RFID transponders.
 


1.3 The use of Inkjet Printed Self-Sintering Conductive Ink to fabricate epidermal antennas
The recently introduced inkjet printing technology with ambient-sintering has been successfully investigated for the fabrication of epidermal antennas suitable for Radiofrequency Identification (RFID) and Sensing. The attractive feature of this manufacturing process is the possibility to use low-cost printers without any high-temperature curing. In spite of the estimated maximum achievable conductivity of the ink (sUHF = 1 x 105 S/m) in UHF-RFID band is two orders of magnitude lower than that of the bulk copper, a three-fold printing process provides the same on-skin radiating performance as manufacturing technologies using bulk conductors. Experiments demonstrated that the epidermal antennas printed on PET substrate are insensitive to moderate mechanical stress, like the natural bending occurring over the human body, and to the possible exposure to body fluids (e.g. sweat). Moreover, the electromagnetic response remains stable over the time when the printed layouts are coated with biocompatible membranes.







1.4 Integration of Skin polymeric flexible batteries onto Skin Antennas

For the acceptance of bio-integrated devices in daily life, radio-systems must be developed that are minimally invasive to the skin, and they must have ultra-low profile local power sources to support data-logging functionality without compromising shape-conformability. We have investigated a tightly integrated multilayer battery-antenna system (65 ×23 mm^2) that is ultra-thin (just 200 μm), flexible, and lighter than 1 g, making it suitable for epidermal applications. The negative electrode (anode) current collector of the battery is an RFID tag antenna coated by a conductive polymer (Pedot:PSS) working as anode material. Since the battery is a dynamic device, subjected to discharging, the antenna design must include the variable dielectric properties of the conductive polymer that are here first characterized in the UHF band for real charge/discharge battery conditions. The communication performance of the prototype composite device has been hence evaluated through the measurement of the realized gain of the tag antenna (-19.6 dBi at 870 MHz) when it was placed directly onto a volunteer's forearm.  The read range of 1.3 - 3 m is suitable for occasional data download from the epidermal data-logger when the user comes close to a reader-equipped gate.





              


1.5 The use of Graphene-oxide as bio-compatible sensitive nanomaterial onboard skin antennas
The monitoring of the human breathing process, including the presence of biomarkers, is of growing interest in noninvasive diagnosis of diseases. We have developed a wearable radiofrequency identification device hosting a flexible antenna suitable for integration into a facemask and a sensor made of graphene oxide sensitive to the humidity variations. The resulting sensor tag was characterized in reference conditions while its communication performance was estimated by electromagnetic simulations as well as by measurements over a simplified model of the human head. Finally, the whole system was tested on a volunteer and was experimentally demonstrated to can detect the inhalation/exhalation cycles and abnormal patterns of respiration like the apnea by measuring the changes in graphene oxide resistance.

                 



Wireless Monitoring of Breath by means of
Graphene Oxide-based RFID Wearable Sensor



2. Proof of Concepts



          










2.1 Use of Epidermal Sensors to Restore Peripheral Thermal Feeling

Finger-Augmented Devices (FAD) identify a particular wearable technology suitable to turn the human fingers into enhanced sensing surfaces for advanced human-computer interfaces. The feasibility of a full on-body UHF RFID-based FAD has been investigated for the first time. The system is aimed at providing impaired people suffering from a lack of thermal feeling, due to pathological disorders, with a real-time feedback of the temperature sensed by the fingertips. The considered RFID-FAD comprises an epidermal tag suitable to conformal application over the fingertip and an interrogation wrist patch antenna. The electromagnetic challenge concerns the possibility to establish a robust RFID link when both the reader antenna and the passive fingertip tag are attached onto the lossy human skin. The occurring near-field interaction is modeled by a two-port system and experimentally tested by means of a 3D hand mockup made by additive manufacturing. Simulations and measurement permitted to derive the upper-bound performance and to estimate the required power budget. The idea was finally demonstrated with a proof of concept in a realistic application.
 

                      
to Restore Peripheral Neuropathy


Finger-Augmented Device to restore
peripheral thermal feeling


RADIOFingerTip: estimation of the temperature
    




 





2.2 Clinical Trial at the University of Tor Vergata Hospital of Wireless Epidermal Temperature Sensor in Real Conditions

Body temperature is among most important biometric indicators that are normally checked in both domestic and hospital environments. The way to collect such parameter could be dramatically improved thanks to the Epidermal Electronics technology enabling plaster-like devices suitable to on-skin temperature sensing and capable of wireless communication with an electromagnetic reading module. The practical applicability of an eco-friendly battery-less epidermal thermometer, compatible with the UHF RFID standard, has been finally discussed by the help of experimentation with some volunteers upon our University Hospital, following an authorized Clinical Trial. Comfortable reading procedures can be applied for both the operator and the patient. Experiments revealed a non-negligible sensitivity of the temperature measurement versus the mutual distance between the reader and the sensor, that must be removed by a proper threshold filtering. Finally, the analysis of the sensor response for different placement position over the body, demonstrated that the axilla and chest loci provide only 0.6°C deviation from a reference tympanic measurement and are well accepted by the user which does not complain about the presence of the sensor.



II. LIST OF PUBLICATIONS

Journals Papers

 

  1. S. Amendola, G. Bovesecchi, A. Palombi, P. Coppa, G. Marrocco, “Design, Calibration and Experimentation of an Epidermal RFID Sensor for Remote Temperature Monitoring”, IEEE Sensors Journal, Vol.16, N.19, pp. 7250-7257, 2016

 

  1. S. Amendola, G. Marrocco, “Optimal Performance of Epidermal Antennas for UHF Radiofrequency Identification and Sensing”, IEEE Transactions on Antennas and Propagation, vol. 65, no. 2, pp. 473–481, Feb. 2017.

 

  1. S. Amendola, A. Palombi and G. Marrocco, “Inkjet Printing of Epidermal RFID Antennas by Self-Sintering Conductive Ink”, IEEE Trans. Microwave Theory Tech. – in press

 

  1. M. C. Caccami, M. P. Hogan, M. Alfredsson, G. Marrocco and J. C. Batchelor, “A Tightly Integrated Multilayer Battery-Antenna for RFID Epidermal Applications”, IEEE Trans. Antennas Propagat.  DOI: 10.1109/TAP.2017.2780899

 

  1. V. Di Cecco, S. Amendola, and G. Marrocco, “Numerical and Experimental Characterization of Wrist-Fingers Communication Channel for RFID-based Finger Augmented Devices”, IEEE Trans. Antennas Propagat. - under review

 

  1. M. C. Caccami, M- Y. S. Mulla, C. Di Natale, G- Marrocco, “Graphene Oxide-based Radiofrequency Identification Wearable Sensor for Breath Monitoring”, IET Microwave and Antennas Journal, - under review

 

  1. M.C. Caccami and G. Marrocco, “Electromagnetic Modeling of Self-tuning RFID Sensor Antennas in Linear and Nonlinear Regimes”, IEEE Trans. Antennas Propagat. - under review

 

 

 

Conferences Papers

 

  1. S. Amendola, G. Marrocco, “Epidermal UHF antennas for skin sensing: fundamental limitations and optimal performance”, XXI RiNEm Riunione Nazionale di Elettromagnetismo, Parma, Settembre 2016.
  2. S. Amendola, G. Bovesecchi, P. Coppa  and G. Marrocco, “Thermal characterization of epidermal RFID sensor for skin temperature measurements,” 2016 IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, Fajardo, Puerto Rico, June 26 - July 1, 2016, pp. 461 - 462. DOI: 10.1109/APS.2016.7695939
  3. S. Amendola, A. Palombi, L. Rousseau, G. Lissorgues, and G. Marrocco, “Manufacturing technologies for UHF RFID epidermal antennas,” European Microwave Conference (EuMC), London, Oct. 2016.
  4. S. Amendola, G. Marrocco “Epidermal UHF Antennas for Skin Sensing: Fundamental Limitations and Optimal Performance”, 2016 USNC-URSI, Puerto Rico, June 26 - July 1, 2016
  5. M. C. Caccami, C. Miozzi, M. Y. S. Mulla, C. Di Natale, and G. Marrocco, “An Epidermal Graphene Oxide-based RFID Sensor for the Wireless Analysis of Human Breath,” 8th Annual IEEE International Conference on RFID Technology and Applications, 20 - 22 September 2017, Warsaw, Poland. DOI: 10.1109/RFID-TA.2017.8098641
  6. M. C. Caccami, M. P. Hogan, M. Alfredsson, G. Marrocco, and J. C. Batchelor, “Development of a new class of on-skin radio-sensors boosted by thin polymer-based batteries,” IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes, 20 - 22 September 2017, Pavia, Italy
  7. M. C. Caccami, M.Y. S. Mulla, C. Di Natale, and G. Marrocco, “Wireless Monitoring of Breath by means of a Graphene Oxide-based Radiofrequency Identification Wearable Sensor,” 11th European Conference on Antennas and Propagation, 19 - 24 March 2017, Paris, France, DOI: 10.23919/EuCAP.2017.7928355
  8. C. Miozzi, S. Amendola, A. Bergamini, G. Marrocco, “Reliability of a re-usable wireless Epidermal temperature sensor in real conditions”, IEEE  Body Sensor Networks (BSN) 2017,  Eindhoven (Netherlands), May 2017. DOI: 10.1109/BSN.2017.7936016
  9. C. Miozzi, S. Amendola, A. Bergamini, G. Marrocco, “Clinical Trial of Wireless Epidermal Temperature Sensors: preliminary results”, EMBEC’17 & NBC’17 Conference,  Tampere (Finland), June 2017. DOI: 10.1007/978-981-10-5122-7_260
  10. C. Miozzi, S. Amendola, A. Bergamini, G. Marrocco, “Clinical Trial of Wireless Epidermal Temperature Sensors: preliminary results”, EMBEC’17 & NBC’17 Conference,  Tampere (Finland), June 2017. DOI: 10.1007/978-981-10-5122-7_260
  11. V. Di Cecco, S. Amendola, P.P. Valentini, and G. Marrocco, “Finger-Augmented RFID System to Restore Peripheral Thermal Feeling”, IEEE International Conference on RFID, Arizona, USA, May 2017. DOI: 10.1109/RFID.2017.7945587
  1. M. C. Caccami, C. Miozzi, V. Greco, and G. Marrocco, “Epidermal Radio-Sensors for Wireless Detection of Physiological Parameters and Sense Augmentation”, 12th European Conference on Antennas and Propagation (EuCAP 2018), London (UK), 9-13 April 2018.
  2. C. Miozzi, S. Guido, G. Saggio, E. Gruppioni and G. Marrocco, “Feasibility of an RFID-based Transcutaneous Wireless Communication for the Control of Upper-limb Myoelectric Prosthesis”, 12th European Conference on Antennas and Propagation (EuCAP 2018), London (UK), 9-13 April 2018.
  3. (Under review) C. Miozzi, S. Nappi, S. Amendola, G. Marrocco, “A General-Purpose Small RFID Epidermal Datalogger for Continuous Human Skin Monitoring in Mobility”, International Microwave Symposium (IMS 2018), Philadelphia, Pennsylvania (US), 10-15 June 2018.



Book Chapters

 

  1. S. Amendola, C. Occhiuzzi, and G. Marrocco, “More than Wearable: Epidermal Antennas for Tracking and Sensing”, Chapter of Electromagnetics of Body-Area Networks: Wearable Antennas, Propagation, and RF Systems, Douglas H. Werner and Zhi-Hao Jiang (Editors), Wiley/IEEE, July 2016.



III. AWARDS

1. Best Paper Award at IEEE RFID-TA 2017  Warsaw, Polland

M. C. Caccami, M. Y. S. Mulla, C. Di Natale, and G. Marrocco

“An Epidermal Graphene Oxide-based RFID Sensor for the wireless analysis of human breath2

 

2. Best Student Paper Award at EUCAP-2017, Paris

M. C. Caccami, M. Y. S. Mulla, C. Di Natale, and G. Marrocco

“Wireless Monitoring of Breath by means of a Graphene Oxide-based Radiofrequency Identification Wearable Sensor”

 

3. Best Paper Finalist IEEE-RFID 2017, Phoenix (US)

V. Di Cecco, S. Amendola, P.P. Valentini, and G. Marrocco, “Finger-Augmented RFID System to Restore Peripheral Thermal Feeling”

 

4. Best Paper Award at IEEE 14th International Conference on Wearable and Implantable Body Sensor Networks (BSN2017), Eindhoven (The Netherlands),

C. Miozzi; S. Amendola; A. Bergamini; G. Marrocco, “Reliability of a Re-usable Wireless Epidermal Temperature Sensor in Real Conditions”   



IV. DISSEMINATION

The proof of concepts developed during this research have been demonstrated to the public during the 2017 edition of Romecap (2017.romecup.org) where visitors were allowed to test the epidermal sensors for the wireless measurement of body temperature and for sense augmentations.