Author Archives: Flexible Electronics Group @ POSTECH

The Dermal Abyss: Interfacing with the Skin by Tattooing Biosensors

Journal: ISWC

Author: Katia Vega, Nan Jiang and Xin Liu et al.

Affiliation: MIT Media Lab, Harvard Medical School

Publication date: 2017.09.11

Summarized by Jinpyeo Jeung

 

– Health monitoring tattoos (Fig. 1)
v. Glucose, pH and Sodium sensor.
v. principle: Using biosensor ink for tattoos.

fig1.png

<Fig. 1>

 

– Biosensors (Fig.2)
v. Sodium biosensor: diaza-15-crown-5. Selectively bind to Na+ ions.
v. pH biosensor: anthocyanin.(Fig. 3)
v. Glucose biosensor: extracted from reagent strips.

fig2.png

<Fig. 2>

fig3.png

<Fig. 3>

 

– Result
v. Glucose biosensor without glucose and with glucose (Fig. 4)
v. pH biosensor at pH 8.0 and pH 7.0 (Fig. 5)
v. Sodium biosensor with 100mmol/L Na+ ions under visible light and UV light (Fig. 6)
v. designs made by a tattoo artist in ex vivo pig skin.(Fig.7)

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<Fig. 4>

fig5.png

<Fig. 5>

fig6.png

<Fig. 6>

fig7.png

<Fig. 7>

 

– Application by monitoring health status
v. Diabetes.
v. Dehydration.
v. pH Balance.

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Wearable Ring-Based Sensing Platform for Detecting Chemical Threats

Journal: ACS SENSORS

Author: J. R. Sempionatto and Joseph Wang et al.

Affiliation: University of California, United States

Publication date: 2017.10.11

Summarized by Inyeol Yun

 

– Ring-based Chemical Sensor (Fig. 1)
v. Explosives (DNT, H2O2) and nerve agent (MPOx) sensor
v. Printing fabrication (Fig. 2)
v. Sensing principle: redox reaction between working electrode and chemical (Fig. 3)

fig1

Fig. 1

fig2.png

Fig. 2

fig3.png

Fig. 3

 

– Materials
v. Working electrode: carbon ink (1), carbon-Prussian blue ink (2)
v. Reference, counter electrode: Ag/AgCl ink
v. All inks were purchased

 

– Result
v. Liquid-phase threat detection at the ring-based electrochemical system (Fig. 4)
v. Vapor-phase threat detection at the ring-based electrochemical system (Fig. 5)
v. Selectivity test (Fig. 6)

fig4.png

Fig. 4

fig5.png

Fig. 5

fig6.png

Fig. 6

A Strain-absorbing Design for Tissue–machine Interfaces Using a Tunable Adhesive Gel

Author: Sungwon Lee, Takao Someya et al.

Affiliation: The University of Tokyo, Japan Science and Technology Agency (JST)

Publication date: 2014.12.19

Summarized by Seongmin Park

 

– Structure
v. 1.4 μm PET substrate, 20 nm Au word line, 50 nm Au bit line, 30 nm DNTT active layer, 200 nm parylene gate dielectric layer

fig1

Fig. 1

v. Only the area covered by photopatterned gel maintains an adhesive contact during measurement  the floating parts of the device absorb strain

fig2.png

Fig. 2

fig3.png

Fig. 3

 

–Adhesive gel property
v. adhesion strength: Adhesion strength is enough for supporting a coin (5g)

fig4.png

Fig. 4

v. Adhesive gel constituents

fig5

Fig. 5

v. Properties controlled by PVA concentration

1. Modulus of adhesive gel

fig6.png

Fig. 6

2. Adhesion strength vs. glass

 

fig7.png

Fig. 7

3. Resistance and capacitance (Dashed line represents the capacitance.)

fig8.png

Fig. 8

– Results
v. OTFT performance: 10 times 100% compressive strainàremains its performance

fig9.png

Fig. 9

v. Device on a balloon: Can endure ~100% compressive strain

fig10.png

Fig. 10

fig11.png

Fig. 11

Self-assembled three dimensional network designs for soft electronics

Journal: Nature communications

Author: Kyung-In Jang and John A. Rogers et al.

Affiliation: Daegu Gyeongbuk Institute of Science and Technology, Northwestern University

Publication date: 2017.06.21

Summarized by Jinpyeo Jeung

 

– 3D helical coil (Fig.1)
v. 2D structures limit performance for systems that require low modulus, elastic mechanics in compact designs.
v. 2D precursors spontaneously transform into desired 3D shapes.
v. Compressive forces induced by releasing the prestrain cause the 2D precursor to geometrically transform.
v. Two ends include small discs that form strong covalent siloxane bonds to and substrate.

fig1.png

Fig. 1

 

– Result
v. Enables high levels of strechability and mechanical robustness, without the propensity for localized crack formation or fracture.
v. The elastic stretchability of the 3D helices significantly exceeds that of the 2D serpentines. (Fig.2)
v. Deformations of the 2D serpentine lead to sharp, unavoidable stress concentrations at the arc regions but 3D helices shows uniform stress. (Fig.3)

fig2.png

Fig. 2

fig3.png

Fig. 3

 

– Application
v. Actual appearance. (Fig. 4, Fig. 5)
v. It can be applied to various wireless, skin-compatible electronics. (Fig. 6)

fig4.png

Fig. 4

fig5

Fig. 5

fig6.png

Fig. 6

Accelerated Wound Healing on Skin by Electrical Stimulation with a Bioelectric Plaster

Journal: Advanced Healthcare Materials

Author: Hiroyuki Kai and Matsuhiko Nishizawa et al.

Affiliation: Tohoku University, Japan

Publication date: 2017.09.20

Summarized by Inyeol Yun

 

– Bioelectric Plaster (Fig. 1)
v. Wound healing on skin involves cell migration and proliferation in response to endogenous electric current.
v. External electrical stimulation is used to promote these biological processes for the treatment of chronic wounds.
v. An enzymatic biofuel cell (EBFC) that generates ionic current along the surface of the skin by enzymatic electrochemical reactions for more than 12h. (Fig. 2)

fig1

Fig. 1

fig2.png

Fig. 2

 

– Materials
v. Cathode : carbon fiber fabric coated with carbon nanotubes, on which reducing enzyme bilirubin oxidase
v. Anode : carbon fiber fabric coated with carbon nanotubes, on which oxidizing enzyme fructose dehydrogenase
v. Hydrogel : citrate buffer solutions with different concentrations of fructose.
v. Stretchable resistor : PEDOT/PU film

 

– Result
v. Time-dependent current changes of the bioelectric plaster with different external resistances and citrate buffer solutions with different concentrations. (Fig. 3)
v. Changes of wound width and height of Group A (gray), Group B (red), and Group C (blue) (Fig. 4)
v. Microscopy images of skin sections at the wound at day 7: a) the boundary between normal tissue and healed tissue, b) the area of normal tissue, c) the area of healed tissue, d) dermis, e) fat tissue (Fig. 5)  Group C > Group A on scar after healing, wound closure speed.

fig3

Fig. 3

fig4

Fig. 4

fig5.png

Fig. 5

 

– Reference
v. https://en.wikipedia.org/wiki/Enzymatic_biofuel_cell (accessed September 26, 2017)

Self-Powered, Paper-Based Electrochemical Devices for Sensitive Point-of-Care Testing

Journal: Advanced Materials Technologies

Publication date: 2017.08.22

Summarized by Inyeol Yun

 

– Self-powered, paper-based electrochemical devices (SPEDs)
v. Structure (Fig. 1)
v. Electrochemical detection (Fig. 2), colorimetric test
v. Triboelectric generator (TEG) (Fig. 3)

fig1

Fig. 1

fig2

Fig. 2

fig3

Fig. 3

 

– Fabrication
v. Biomarker part (Fig. 4)
v. TEG part (Fig. 5)

fig4

Fig. 4

fig5

Fig. 5

 

– Result
v. Electrochemical detection (Fig. 6)
v. TEG (Fig. 7)

fig6

Fig. 6

fig7

Fig. 7

Highly Flexible and Efficient Fabric Based Organic Light-Emitting Devices for Clothing-Shaped Wearable Displays

Journal: Scientific Reports

Publication date: 2017.07.25

Summarized by Seongmin Park

 

– Methods to achieve actual clothing-shaped information displays

  1. Attaching a display panel onto a piece of clothing → Flexibility decreases
  2. Fabricating of light emitting fiber → Low emission performance
  3. Fabricating an information display onto a fabric → Best choice

– Novel Concept

v. Spin coating of the silane-based film on fabric (Fig. 1, 2)

fig1

Fig. 1

fig2

Fig. 2

– Structure

  1. Base Structure (Fig.3)

fig3

Fig. 3

     2. Endurance vs. Number of dyads (Fig. 4, 5)

fig4

Fig. 4

fig5

Fig. 5

     3. Optimized Structure (Fig. 6)

fig6

Fig. 6

     4. Good Endurance

fig7

Fig. 7

 

– Results

  1. Similar performance (Fig. 8)

fig8

Fig. 8

     2. Light emitting performances vs. bending radius (Fig. 9)

fig9

Fig. 9

     3. Comparison between OLEDs on fabric and OLEDs on PET (Fig. 10)

fig10

Fig. 10

     4. Cyclic bending with bending radius of 1 cm (Fig. 11)

fig11

Fig. 11