700 IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. 53, NO. 3, AUGUST 2011

Ultrathin and Flexible Screen-Printed Metasurfacesfor EMI Shielding Applications

Lin Biao Wang, Student Member, IEEE, Kye Yak See, Senior Member, IEEE, Jun Wu Zhang, Budiman Salam,and Albert Chee Wai Lu, Member, IEEE

Abstract—An ultrathin, lightweight, and flexible metasurface forband-stop electromagnetic interference (EMI) shielding purposehas been designed and fabricated using screen-printing technol-ogy. Using a 1.8 GHz band-stop EMI shield as a design example, aprototype of a screen-printed metasurface has been validated usingmeasured and numerically computed results. Hence, screen print-ing can be an attractive option for flexible and lightweight shieldsthat can be easily applied on the walls and windows of a room toblock specific wireless communication band so as to protect criticalelectronics instruments from possible EMI.

Index Terms—Electromagnetic interference (EMI), electromag-netic shielding, metasurfaces, screen printing.

I. INTRODUCTION

DUE to the exponential growth of wireless communica-tion, portable communication devices are common sights

in our daily life. However, with the heavy reliance on wirelesscommunications, an increasing number of base stations are ex-pected to ensure good wireless coverage. Such a trend has posedpotential electromagnetic interference (EMI) risk or radiationhazards for some buildings. For examples, the intensive careunit in a hospital, where life-supporting medical instrument ishoused and storage space in a warehouse, where explosive ma-terial or flammable liquid is stored [1]–[3]. The conventionalapproach to block intentional wireless communication is to in-stall a solid metallic shielded enclosure. However, this approachcan be costly and labor intensive. In addition, structural loadingto existing building has to be considered due to the weight ofthe shielded enclosure [4]. Inspired by the properties of metasur-faces, this paper explores the use of a screen-printing techniqueto realize band-stop EMI shield that can be easily applied aswallpaper on the walls of a room without the structural loadingissue to existing architecture.

Frequency selective surface (FSS) has been studied exten-sively since the 1960s. It was deployed in the design of ran-domes, reflectors, and reflect-array lenses, mostly for defenseapplications [5], [6]. Recent work and study in 2-D metama-

Manuscript received November 29, 2010; revised May 13, 2011; acceptedJune 2, 2011. Date of publication July 14, 2011; date of current version August18, 2011.

L. B. Wang, K. Y. See, and J. W. Zhang are with the Schoolof Electrical and Electronic Engineering, Nanyang Technological Univer-sity, 639798 Singapore (e-mail: wang0474@e.ntu.edu.sg; ekysee@ntu.edu.sg;zhan0291@e.ntu.edu.sg).

B. Salam and A. C. W. Lu are with the Large Area Processing Pro-gram, Singapore Institute of Manufacturing, 638075 Singapore (e-mail:budimans@SIMTech.a-star.edu.sg; cwlu@SIMTech.a-star.edu.sg).

Digital Object Identifier 10.1109/TEMC.2011.2159509

terials, also known as metasurfaces or metafilms, have shownstable resonant frequencies that are independent of the angleof the incident wave [7]–[10]. Such properties are desirable forlarge area frequency selective shielding, where the incident an-gle of an external EMI wave can be unknown. This propertyhas been well explained theoretically [11] and will not be re-peated here. This paper extends the work done and realizes themetasurfaces for practical EMI shielding applications. There arevarious fabrication techniques to realize metasurfaces, usuallyon rigid structure and limited to small area [12], [13]. Screenprinting is explored here as it has the ability to fabricate largevolume reel-to-reel printing, making it an attractive option forEMI shielding that occupies a large surface area.

In this paper, the preliminary design of the metasurfaces withband rejection characteristic begins with the use of the equiv-alent circuit model of an infinite array of Jerusalem crosses todetermine its frequency response for different geometrical pa-rameters. The design is finalized through fine tuning the bandrejection frequency using a full-wave simulation tool. The final-ized design is implemented by screen printing of a silver pasteonto a flexible polyethylene terephthalate (PET) substrate [14].An ultrathin and flexible band-stop EMI shield prototype thatblocks the 1.8 GHz GSM band is fabricated with the screen-printing technology and its band rejection EMI shielding per-formance at 1.8 GHz is also demonstrated experimentally.

II. DESIGN OF BAND-STOP EMI SHIELD

A. Fabrication Process

PET is selected as the substrate for screen printing as it of-fers excellent flexibility and durability. The chosen PET has athickness h of 0.1 mm and dielectric constant εr of 2.2. Thescreen-printing process uses an ink blocking stencil, which de-fines the area to be patterned onto the substrate with conductivesilver paste. A circular disk of radius 130 mm is printed on thesubstrate to characterize the electrical property of the coatedsilver paste. Based on a four-point measurement technique [15],the conductivity of the coated silver paste disk is found to be 2×106 S/m. The conductivity is lower than pure silver due to themixture of adhesive and slider powder in the silver paste. How-ever, the conductivity is high enough for practical EMI shieldingapplications. The thickness of the printed silver paste is foundto be 10 μm with the help of post curing profile measurement.As both the silver powder and adhesive are nonferrous materi-als, the relative permeability μr will be unity. These electricaland geometrical parameters will be used later in the full-wavesimulation analysis of the band-stop EMI shield.

0018-9375/$26.00 © 2011 IEEE

WANG et al.: ULTRATHIN AND FLEXIBLE SCREEN-PRINTED METASURFACES FOR EMI SHIELDING APPLICATIONS 701

Fig. 1. Geometrical parameters of Jerusalem crosses and the equivalent circuitmodel.

B. Band-Stop EMI Shield Design

As a first step, the band reject frequency of the shield hasto be determined. The Jerusalem crosses pattern is selected,as it is more compact in design as compared to conventionalcross dipoles. The loaded ends of Jerusalem crosses offer anadditional degree of freedom to fine tune the final design toachieve the desired band rejection frequency accurately. Thedesign procedure for the band-stop shield will be as follows.

1) Based on the equivalent circuit model for an infinite arrayof Jerusalem crosses, the band rejection frequency due toeach critical geometrical parameter of Jerusalem crosseswill be studied.

2) Obtain the preliminary dimensions of the geometrical pa-rameters of the unit cell so as to achieve the desired rejec-tion band frequency.

3) Perform full-wave simulation on the preliminary designedband-stop EMI shield and fine tune the critical geometri-cal parameters to achieve the desired band rejection fre-quency; and

4) Experimental validation of the fabricated band-stop EMIshield.

The aforementioned design steps will be described in de-tail in the following section. Preliminary design through para-metric study on the various critical geometrical dimensions ofJerusalem crosses using a full-wave model and simulation canbe computationally prohibitive. Hence, the equivalent circuitmodel of Jerusalem crosses will be used to obtain the prelimi-nary design without heavy computational effort [16]. The equiv-alent circuit of an infinite array of Jerusalem crosses is describedin [17]. Fig. 1 shows the geometry parameters and equivalentcircuit model of an array of Jerusalem crosses.

Each Jerusalem cross unit cell exhibits both inductive and ca-pacitive reactance when excited by an incident electric field. Thecapacitance is due to the capacitive coupling between adjacentcrosses while the inductance is due to the straight conductorsof the cross. XL and BC are the normalized (with respect tothe free-space impedance) inductive reactance and capacitivesusceptance of the equivalent circuit model, respectively. XL

and BC are given as follows:

XL = F (p,w, λ, θ)

=pcosθ

λ[G (p,w, λ, θ) − ln (sinβ)] (1)

where

G(p,w,λ, θ) =

0.5(1 − β2)2 [(1 − (β2/4))(C+ + C−) + 4β2C+C−](1−(β2/4))+β2(1+(β2/2)−(β4/8))(C+ +C−)+2β6C+C−

(2)

β = sin(

πw

2p

)(3)

C± =1√

1 ± (2p sin θ/λ) − (p cos θ/λ)2− 1 (4)

BC =4l

pF (p, s,λ, θ) +

4 (2w + s)p

F (p, p − l,λ, θ) (5)

where p is the periodicity of the unit cell, w is the width ofthe conductive strip, l is the length of the loaded ends of theJerusalem cross, s is the separation distance between adjacentunit cells, λ is the wavelength of the incidence plane wave, andθ is the angle of incidence between the plane wave and screen.Equations (1)–(5) are valid when f < c/p(1 + sinθ), where c isthe speed of light [18].

Once the equivalent circuit elements are found, the reflectionand transmission S-parameters S11 and S21 of the metasurfacecan be evaluated with ABCD matrices as follows [19]:

S11 =A + B − C − D

A + B + C + D(6)

S21 =2(AD − BC)

A + B + C + D(7)

where A is 1, B is 0, C is the normalized admittance of the LCbranch, and D is 1.

XL is a function of its periodicity p, which is dependent on thelength of the cross and BC is a function of the conductor lengthof the loaded ends l and the separation distance between adjacentcells s. The geometrical parameters p and s are varied to extractXL and BC , and then, S21 is computed. By performing theparametric study on p and s, the preliminary design to obtaina resonant frequency f 0 of around 1.8 GHz can be achievedefficiently. By narrowing the range of p and s, we could proceedwith the use of full-wave modeling and simulation to furtherfine tune the final design.

The suggested equivalent circuit model provides a quick esti-mation of f 0 . However, the analytical equations presented ear-lier do not include the substrate. It is expected that the presenceof the dielectric substrate shifts the f 0 downwards [20], [21].The shift of f 0 is a function of the substrate thickness. Forthe proposed screen-printed metasurface with substrate on oneside, f 0 will shift by a factor between unity and

√(εr + 1)/2

depending on the substrate thickness. For the given substratethickness (t = 0.1 mm), it has been shown in [5] that the shiftin f 0 is negligible as t (0.1 mm) < λ0 /100 (1.7 mm), where λ0is the resonant wavelength of the structure.

III. FULL-WAVE ANALYSIS OF DESIGN

To accurately predict the resonant frequency of the rejectionband and its corresponding shielding performance, a full-wave

702 IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. 53, NO. 3, AUGUST 2011

Fig. 2. 3-D EM simulation model to evaluate the SE of the band-stop EMIshield.

simulator CST Microwave Studio, which is based on a finiteintegration technique, is employed for the simulation [22]. The3-D geometrical model to evaluate the performance of the band-stop EMI shield is depicted in Fig. 2. The model is constructedto closely resemble the fabricated band-stop EMI shield and theexperimental validation setup.

To replicate as close to the measurement setup as possible,the horn antennas are modeled, even if they requires exten-sive modeling and computational efforts. The dimension of thewhole solution domain is 350 mm × 350 mm × 1200 mm. Inthe simulation, absorbing boundary conditions are enforced onall the six faces of the defined volume. Both horn antennas areplaced at a distance of 300 mm away from the band-stop shieldin order to ensure that far-field criterion is met.

Two planes of symmetry are used, with one in the y–z planeand another in the x–y plane. We take advantage of the planesof symmetry to reduce the computational time. Nx , Ny , and Nz

denote the number of gridded cells in x-, y-, and z-axes, respec-tively. In the simulation model, the whole volume is discretizedinto a Cartesian mesh of gridded cells. Nx , Ny , and Nz are 94,96, and 273, respectively. The total number of cells is 2.4 mil-lion with the use of planes of symmetry. Adaptive nonuniformmeshed grids are used so that finer cells are distributed aroundthe band-stop shield for better solution accuracy. The maximumand minimum grid cells are 6.7 and 0.0033 mm, respectively.The substrate thickness (0.1 mm) and its electrical properties(εr = 2.2 and μr = 1) as well as the silver paste thickness(10 μm) and its electrical properties (σ = 2 × 106 S/m and μr =1) are taken into account for the simulation. With one horn an-tenna as the transmitting source and the other as the receivingport, the transmission coefficient S21 of the simulated modelis obtained. By obtaining S21 with and without the band-stopEMI shield, the shielding effectiveness (SE) of the shield can bedetermined as follows [23]:

SEdB = S21, without shield − S21, with shield (8)

where S21,without shield is the transmission coefficient withoutthe EMI shield and S21,with shield is the transmission coeffi-cient with the EMI shield. The simulated S21 between the hornantennas with and without the shield are shown in Fig. 3.

Fig. 3. Simulated S21 between the horn antennas without and with the band-stop EMI shield.

TABLE IGEOMETRICAL DIMENSIONS FOR THE FINAL FSS SHIELD

Fig. 4. Comparison of simulated S21 for a free-standing band-stop Jerusalemcross element being excited with an incident wave at different angles.

Through full-wave simulation, the geometrical dimensionsfor the different parameters are fine-tuned to achieve the finaldesign. Table I shows the final geometrical dimensions of theband-stop EMI shield. A strong resonant frequency at 1.8 GHzis clearly observed with the designed band-stop EMI shield.

To check the impact of the angle of the incident wave onthe resonant frequency of the shield, simulations with incidentwave of various angles (0◦, 20◦, 40◦, and 60◦) are carried outfor a free-standing band-stop shield. Fig. 4 shows the simulatedS21 with an incident wave at various angles of incidence. Theresults indicate that the resonant frequency of the shield is inde-pendent of the angle of the incident wave. It is important, as the

WANG et al.: ULTRATHIN AND FLEXIBLE SCREEN-PRINTED METASURFACES FOR EMI SHIELDING APPLICATIONS 703

Fig. 5. Picture of fabricated ultrathin and flexible band-stop EMI shield.

Fig. 6. Experimental setup for measuring SE of band-stop EMI shield.

band-stop frequency shall remain stable regardless of the direc-tion of external EMI signal.

IV. RESULTS AND EXPERIMENTAL CHARACTERIZATION OF

BAND-STOP EMI SHIELD

Extending from the simulated case study, a prototype of theband-stop EMI shield is fabricated. The geometrical dimensionsare the same as that given in Table I. The design is fabricatedusing screen-printing technology. Fig. 5 shows the photographof the band-stop EMI shield fabricated. The size of the prototypeis 450 mm by 450 mm.

Due to the size of each Jerusalem cross, it is impossible tomeasure the SE of the band-stop shield using the transmissionline test jig methods in the gigahertz range, as the cross-sectionalarea of the test jig is much smaller than the dimension of theJerusalem cross to ensure TEM wave propagation [24]. Hence,the measurement method proposed in [25] is adopted to measurethe SE of the band-stop shield. The measurement setup is shownin Fig. 6. This measurement setup overcomes the edge contactproblem, as the fabricated prototype is ultrathin.

A pair of double-ridged waveguide horn antennas EMCO3115 (1–18 GHz) is chosen to transmit and receive the EMwave propagating across the band-stop shield for their direc-

Fig. 7. Measured S21 between the horn antennas with and without the band-stop shield.

Fig. 8. Comparison of simulated and measured SEs of the band-stop EMIshield.

tivity and antenna gain. The receiving antenna is placed insidea metallic enclosure while the transmitting antenna is placedon top of it. A square aperture of size 350 mm by 350 mm isinserted on the top of the box and RF absorbers are placedaround both antennas in the measurement setup so as to repli-cate as close as possible the full-wave 3-D simulation model.The absorbers used have reflectivity of −20 dB from 30 MHzto 18 GHz. The distance between each antenna and band-stopEMI shield is 300 mm. The measured results are obtained by avector network analyzer (VNA), RS ZVB8 (300 kHz–8 GHz).Ports 1 and 2 of the VNA are connected to the horn antennasfor the S-parameters measurement. Fig. 7 shows the measuredS21 between the antennas with and without the shield.

Through (8), measured and simulated SEs of the band-stopshield are shown in Fig. 8. By comparing the results obtainedusing simulation with that of measurement, good agreementbetween them can be observed. The measured result shows thatSE of 28 dB at the rejection frequency of 1.8 GHz is achieved.Using SE of 15 dB as benchmark, a rejection bandwidth of

704 IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. 53, NO. 3, AUGUST 2011

200 MHz is achievable. This bandwidth is enough to effectivelyattenuate the GSM 1800 transmission signals.

V. CONCLUSION

In this paper, we have realized a flexible and ultrathin meta-surface using a screen-printing technique for band-stop EMIshielding purposes. The band-stop frequency of the shield isindependent of the angle of the incident wave, making it verysuitable for band-stop EMI shielding applications. Good SE atthe rejection band is demonstrated through both measurementand full-wave simulation. The use of a screen-printing techniqueto fabricate this kind of EMI shield has proven to be a viable op-tion for low cost and high-volume production of wallpaper-typeEMI shielding applications.

REFERENCES

[1] S. W. Shah, M. I. Babar, M. N. Arbab, K. M. Yahya, T. Adnan, andA. Masood, “Cell phone jammer,” in Proc. IEEE Int. Multitopic Conf.,Dec. 2008, pp. 579–580.

[2] C. Sage. (2008). Microwave and radio frequency exposure: A growingenvironmental health crisis. [Online]. Available: http://www.sfms.org

[3] S. Rao, A. Sathyanarayanan, and U. K. Nandwani, “EMI problem formedical devices,” in Proc. Int. Conf. Electomagn. Interference Compat.,Aug. 2002, pp. 21–24.

[4] L. H. Hemming, Architectural Electromagnetic Shielding Handbook—ADesign and Specification Guide. New York: Wiley, 1992.

[5] B. A. Munk, Frequency Selective Surfaces. New York: Wiley, 2000.[6] T. K. Wu, S. W. Lee, and M. L. Zimmerman, “Evaluation of frequency-

selective reflector antenna systems,” Microw. Opt. Technol. Lett., vol. 6,no. 3, pp. 175–179, Mar. 1993.

[7] E. F. Kuester, M. A. Mohamed, and C. L. Holloway, “Averaged transitionconditions for electromagnetic fields at a metafilm,” IEEE Trans. AntennasPropag., vol. 51, no. 10, pp. 2641–2651, Oct. 2003.

[8] C. L. Holloway, M. A. Mohamed, and E. F. Kuester, “Reflection andtransmission properties of a metafilm: With an application to a control-lable surface composed of resonant particles,” IEEE Trans. Electromagn.Compat., vol. 47, no. 4, pp. 853–865, Nov. 2005.

[9] C. L. Holloway, P. Kabos, M. A. Mohamed, E. F. Kuester, J.Gordon, M. D. Janezic, and J. Baker-Jarvis, “Realization of a controllablemetafilm/metasurface composed of resonant magnetodielectric particles:Measurements and theory,” IET Microw., Antennas, Propag., vol. 4, no. 8,pp. 1111–1122, Aug. 2010.

[10] C. L. Holloway, A. Dienstfrey, E. F. Kuester, J. F. O’Hara, A. K. Azad,and A. J. Taylor, “A discussion on the interpretation and characterizationof metafilms-metasurfaces: The two-dimensional equivalent of metama-terials,” Metamaterials, vol. 3, pp. 100–112, 2009.

[11] J. Gordon, C. L. Holloway, and A. Dienstfrey, “A physical expla-nation of angle independent reflection and transmission properties ofmetafilms/metasurfaces,” IEEE Antennas Wireless Propag. Lett., vol. 8,pp. 1127–1130, Oct. 2009.

[12] J. A. Bossard, D. H. Werner, T. S. Mayer, J. A. Smith, Y. U. Tang, R. P.Drupp, and L. Li, “The design and fabrication of planar multiband metal-lodielectric frequency selective surfaces for infrared applications,” IEEETrans. Antennas Propag., vol. 54, no. 4, pp. 1265–1276, Apr. 2006.

[13] J. C. Batchelor, E. A. Parker, J. A. Miller, V. Sanchez-Romaguera, andS. G. Yeates, “Ink jet printing of frequency selective surfaces,” Electron.Lett., vol. 45, no. 1, pp. 7–8, Jan. 2009.

[14] B. Gao and M. M. F. Yuen, “Optimization of silver paste printed passiveUHF RFID tags,” in Proc. Int. Conf. Elecron. Packag. Technol. HighDensity Packag., Aug. 2009, pp. 512–515.

[15] D. K. Schroder, Semiconductor Material and Device Characterization.Hoboken, NJ: Wiley, 2006.

[16] R. J. Langley and A. J. Drinkwater, “Improved empirical model for thejerusalem cross,” IEE Microw. Opt. Antennas, vol. 129, no. 1, pp. 1–6,Feb. 1982.

[17] N. Marcuvitz, Waveguide Handbook. New York: McGraw Hill, 1951.[18] T. K. Wu, Frequency Surface and Grid Array. New York: Wiley, 1995.[19] D. M. Pozar, Microwave Engineering. New York: Wiley, 1998.

[20] T. Cwik, R. Mittra, K. Lang, and T. K. Wu, “Frequency selective screens,”IEEE Antennas Propag. Soc. Newslett., vol. 29, no. 2, pp. 5–10, Apr. 1987.

[21] T. K. Wu, “Dielectric properties measurement of substrate and supportmaterials,” Microw. Opt. Technol. Lett., vol. 3, no. 8, pp. 283–286, Aug.1990.

[22] CST Microwave Studio. (2010). [Online]. Available: www.cst.com[23] C. R. Paul, Introduction to Electromagnetic Compatibility, 2nd ed.

Hoboken, NJ: Wiley, 2006.[24] S. Celozzi, R. Araneo, and G. Lovat, Electromagnetic Shielding. Hobo-

ken, NJ: Wiley, 2006.[25] A. C. Marvin, L. Dawson, I. D. Flintoft, and J. F. Dawson, “A method for

the measurement of shielding effectiveness of planar samples requiring nosample edge preparation or contact,” IEEE Trans. Electromagn. Compat.,vol. 51, no. 2, pp. 255–262, May 2009.

Lin Biao Wang (S’11) received the B.Eng. andM.Sc. degrees in electrical and electronic engineeringfrom Nanyang Technological University, Singapore,in 2006 and 2009, respectively, where he is currentlyworking toward the Ph.D. degree under the guidanceof Dr. See.

His research interests include electromagneticinterference (EMI) reduction techniques, EMI/electromagnetic compatibility modeling, and fre-quency selective shielding.

Kye Yak See (SM’02) received the B.Eng. de-gree from the National University of Singapore,Singapore, and the Ph.D. degree from Imperial Col-lege, London, U.K., in 1986 and 1997, respectively,both in electrical engineering.

Between 1986 and 1991, he was with SingaporeTechnologies Electronics Ltd. as the Head of Electro-magnetic Compatibility (EMC) Centre. From 1991to 1994, he held the position of Lead EMC DesignEngineer in ASTEC Custom Power, Singapore. Heis currently an Associate Professor in the School of

Electrical and Electronic Engineering, Nanyang Technological University, Sin-gapore. He also holds concurrent designations as the Head of the Circuitsand Systems Division and the Director of Electromagnetic Effects ResearchLaboratory. His research interests include EMC design for power electronics,high-speed signal integrity design, and EMC measurement techniques.

Dr. See is the Founding Chair of the IEEE Singapore EMC Chapter and aTechnical Assessor of Singapore Accreditation Council. He was also the Orga-nizing Committee Chairs for the 2006 EMC Zurich Symposium and 2008 AsiaPacific EMC Conference in Singapore. Since January 2011, he has been theTechnical Editor of the IEEE EMC Society Newsletter.

Jun Wu Zhang received the B.Eng.(Hons.) degree inelectrical and electronic engineering from NanyangTechnological University (NTU), Singapore, wherehe is currently working toward the Ph.D. degree.

His research interests include electromagnetic in-terference reduction techniques and RF-energy har-vesting for low-power devices.

WANG et al.: ULTRATHIN AND FLEXIBLE SCREEN-PRINTED METASURFACES FOR EMI SHIELDING APPLICATIONS 705

Budiman Salam received the B.Eng.(Hons.) de-gree from the Institut Sains dan Teknologi Nasional,Jakarta, Indonesia, and the Ph.D. degree from theUniversity of Greenwich, London, U.K., in 1996 and2006, respectively.

He is currently a Research Scientist with theLarge Area Processing Program, Singapore Instituteof Manufacturing Technology, Singapore, a researchinstitute of the Agency for Science, Technology,and Research. His research interests include largearea manufacturing and roll-to-roll patterning and

structuring.

Albert Chee Wai Lu (M’98) received theB.Eng.(Hons.) degree in electrical and electronic en-gineering and the Ph.D. degree in electrical engineer-ing from the University of Manchester Institute ofScience and Technology, Manchester, U.K., in 1994and 1998, respectively.

He is currently the Program Manager and a SeniorScientist with the Large Area Processing Program,Singapore Institute of Manufacturing Technology,Singapore, a research institute of the Agency for Sci-ence, Technology, and Research. He currently leads

a multidisciplinary research team on disruptive manufacturing processes, flex-ible substrates, and multifunctional integration for functional films and printedelectronics.

Dr. Lu was the recipient of the Lee Kuan Yew Award for Mathematics andScience in Singapore and the Institution of Electrical Engineers Prize in U.K.