advances.sciencemag.org/cgi/content/full/4/1/eaap9841/DC1

Supplementary Materials for

Soft, smart contact lenses with integrations of wireless circuits, glucose

sensors, and displays

Jihun Park, Joohee Kim, So-Yun Kim, Woon Hyung Cheong, Jiuk Jang, Young-Geun Park, Kyungmin Na,

Yun-Tae Kim, Jun Hyuk Heo, Chang Young Lee, Jung Heon Lee, Franklin Bien, Jang-Ung Park

Published 24 January 2018, Sci. Adv. 4, eaap9841 (2018)

DOI: 10.1126/sciadv.aap9841

The PDF file includes:

Supplementary Materials and Methods

fig. S1. Fabrication processing steps of the hybrid substrate.

fig. S2. AFM data analysis.

fig. S3. Optical transmittance (black) and haze (red) spectra of the silicone

elastomeric film.

fig. S4. The variation of optical properties against mechanical stretching of the

hybrid substrate (from 0 to 30% in tensile strain).

fig. S5. Original image for the photograph test to identify the clarity of hybrid

substrate.

fig. S6. Wireless display circuit composed of an antenna, a rectifier, and an LED

pixel.

fig. S7. Fabrication procedures of wireless display on the hybrid substrate.

fig. S8. Characteristics of the stretchable, transparent AgNF electrode as antenna.

fig. S9. Characteristics of the Si diode and SiO2 capacitor.

fig. S10. Sequential schematic images to transform to the lens shape.

fig. S11. Mechanism of glucose sensing on graphene channel.

fig. S12. The magnified real-time sensing result (at the first detection of glucose

level) to verify the response time.

fig. S13. Stability of the smart contact lens system.

fig. S14. The relationship between the glucose concentration and luminance of the

LED.

fig. S15. SAR simulation result.

table S1. Comparison with other noninvasive glucose monitoring technologies.

Legends for movies S1 to S4

References (43–45)

Other Supplementary Material for this manuscript includes the following:

(available at advances.sciencemag.org/cgi/content/full/4/1/eaap9841/DC1)

movie S1 (.mp4 format). Embedding procedure of the hybrid substrate in the

contact lens.

movie S2 (.mp4 format). Wireless operation of wireless display with lens shape.

movie S3 (.mp4 format). In vivo test of soft, smart contact lens for wireless

operation.

movie S4 (.mp4 format). In vivo test of soft, smart contact lens for heat

generation test.

Supplementary Materials and Methods

Preparation of the rectifier

The process began by defining p- and n-doped regions on SOI wafer (Soitec, unibond with 300 nm top

p-type Si layer with the resistivity of 14-22 Ω·cm and 400 nm-thick buried oxide layer) via impurity

diffusion. Boron was pre-deposited in the furnace at the temperature of 1,050 °C for 70 sec under the

flow of N2 (1,000 sccm) using RTA to diffuse the boron concentration uniformly across the 300 nm-

thick top silicon wafer. After photo-lithographically patterning the SiO2 (thickness: 300 nm) deposited

by PECVD on the p-doped area, phosphorus was deposited in the RTA furnace at 1,050 °C for 120 sec

under the flow of N2 (1,000 sccm) in order to convert p-type into n-type. Subsequently, the SiO2 and

SiOx on the surface were removed using buffered HF solution. The silicon p-n diode on the SOI wafer

was transferred onto the target substrate system (500 nm-thick parylene/800 nm-thick Cu film/Si wafer)

by etching away the buried oxide layer of SOI wafer with 50% HF solution, and then picking up the Si

diode with PDMS stamp. After transfer, anode and cathode (Cr/Au: 3/100 nm) of diode were deposited

and patterned photolithographically. After that, the capacitor for rectifier was manufactured. In the

capacitor, the bottom electrode is connected to the cathode (n-type side of the diode), and the 300 nm-

thick SiO2, dielectric material for capacitance, is deposited by PECVD. The top electrode of the

capacitor (Cr/Au: 3/100 nm) was also deposited and patterned.

Fabrication of AgNF electrodes for antenna and interconnects

In order to form ultra-long AgNFs, a suspension of Ag nanoparticles (NPK, Korea, average diameter: 40

± 5 nm, solvent: ethylene glycol, concentration = 50 wt.%) was electrospun continuously onto the target

substrate. Then, the electrospun sample was thermally annealed at 150 °C for 30 min to coalesce the Ag

nanoparticles into electrically-conductive AgNFs with an average diameter of 338 ± 35 nm, and these

annealed AgNFs were photolithographically patterned using wet etching process for the antenna and

interconnects.

Graphene synthesis using chemical vapor deposition (CVD) and transfer of graphene on the target

substrate

A Cu foil (Alfa Aesar, item No.: 13382) on a quartz stage was placed in the center of quartz CVD

chamber under low vacuum condition (10 mTorr). After loading, the furnace was heated up to 1,000 °C

under the flow of Ar (200 sccm) and H2 (500 sccm). Under the flow of CH4 (12 sccm) and H2 (500

sccm), the graphene synthesis was carried out for 5 min, and then the furnace was cooled rapidly to

room temperature with flowing Ar (500 sccm). A 200 nm thickness of poly(methyl methacrylate)

(PMMA, Microchem Corp., 950 PMMA) was spun on the graphene sample which is synthesized on the

Cu foil as a supporting layer. The metal foil was removed by floating on a diluted etching solution of

FeCl3: HCl: H2O (1:1:20 vol.%). After the etching process, the PMMA coated graphene layer was

floated onto the deionized water for rinsing. Subsequently, the sample was transferred onto the target

substrate, and the transferred sample was dried in the atmosphere for 4 hours. After drying, the PMMA

layer was dissolved by acetone.

Electrical characterization

The four-point probe method was used for the measurement of sheet resistance using a probe station

with a Keithley 4200-SCS semiconductor parametric analyzer. The electrical characteristics of Si diodes

and real-time sensing of glucose sensor were conducted using a probe station (Keithley 4200-SCS). (i)

The I-V curves of Si diodes were measured with the drain bias (VD) from -5 V to 5 V. (ii) The real-time

sensing of glucose sensor was conducted with the VD of 5 V.

Wireless measurements and operations

For wireless operations of wireless display and soft, smart contact lens, the power is generated and

wirelessly transmitted by the waveform generator (Keysight 33520B) connected with RF power

amplifier (A-300). The transmitted waveform is measured by the oscilloscope (Keysight MSOX3032T).

Thermal characterization

For the thermal characterization during in-vivo test, the temperature was measured by an LWIR camera

(T650sc, FLIR Systems, Wilsonille, OR, USA). The temperature distribution of images and video was

analyzed using the FLIR ResearchIR software (Research IR Max, FLIR Systems).

fig. S1. Fabrication processing steps of the hybrid substrate.

fig. S2. AFM data analysis. SEM image (left) shows the scanned location on the hybrid substrate.

Scale bar, 500 μm. The height profile (right) of AFM image (green line in Fig. 2D) shows negligible

height difference.

fig. S3. Optical transmittance (black) and haze (red) spectra of the silicone elastomeric film.

fig. S4. The variation of optical properties against mechanical stretching of the hybrid substrate

(from 0 to 30% in tensile strain).

fig. S5. Original image for the photograph test to identify the clarity of hybrid substrate.

fig. S6. Wireless display circuit composed of an antenna, a rectifier, and an LED pixel. The

rectifier converts the AC signal induced in the antenna into the DC, and the DC powers the LED pixel

which is connected to the rectifier in parallel.

fig. S7. Fabrication procedures of wireless display on the hybrid substrate.

fig. S8. Characteristics of the stretchable, transparent AgNF electrode as antenna. (A) Sheet

resistance and optical transmittance of the AgNF films as function of area fraction. (B) Relative

change in resistance of AgNF films as a function of strain. (C) Power transmission efficiency of the

AgNF antenna as a function of frequency. (D) Transmitted voltage of the AgNF antenna as a function

of frequency.

fig. S9. Characteristics of the Si diode and SiO2 capacitor. (A) Optical microscopic image of

rectifier. Scale bar, 200 μm. (B) Characteristics of the Si diode. (C) Characteristics of the SiO2

capacitor.

fig. S10. Sequential schematic images to transform to the lens shape. The circuit in the hybrid

substrate was cut off with donut shape. The circuit was located inside the lens mold, and then the

contact lens material is fulfilled. After pressing the upper mold with 313 kPa, followed by curing

process, the circuit is embedded into the contact lens.

fig. S11. Mechanism of glucose sensing on graphene channel. When the glucose approaches to the

functionalized graphene channel. The GOD will convert glucose into gluconic acid in producing a

byproduct, H2O2. After that, H2O2 will be naturally decomposed into O2, electron, proton (H+ ion). In

addition, the protons will increase the major carrier density of graphene channel.

fig. S12. The magnified real-time sensing result (at the first detection of glucose level) to verify the

response time.

fig. S13. Stability of the smart contact lens system. (A) Calibration curves for various glucose

concentrations with the passage of time in artificial tear fluid. (B) Relative change in the rectified

voltages of wirelessly transmitted power as a function of the storage time in artificial tear fluid. (C)

The relative change in luminance as a function of the stretching and releasing cycles (tensile strain of

30%).

fig. S14. The relationship between the glucose concentration and luminance of the LED.

fig. S15. SAR simulation result. The transmitting power sets as 50 W for the extreme environment

test.

table S1. Comparison with other noninvasive glucose monitoring technologies.

Type of

body fluid Type of sensor Method to display results Ref.

Tear Resistive-type RF signal (reflectance, S11) 14

Sweat Electrochemical-

type

Connection with smartphone by

Bluetooth 43

Sweat Colorimetric-type Colorimetric method and NFC

connection for quantitation 44

Saliva Electrochemical-

type

Wireless communication with

customized module (computer) 45

movie S1. Embedding procedure of the hybrid substrate in the contact lens.

movie S2. Wireless operation of wireless display with lens shape.

movie S3. In vivo test of soft, smart contact lens for wireless operation.

movie S4. In vivo test of soft, smart contact lens for heat generation test.