Bioassay on a Robust and Stretchable Extreme Wetting. Substrate through Vacuum-Based Droplet Manipulation

Transcription

1 Supporting Information for A Single-Droplet Multiplex Bioassay on a Robust and Stretchable Extreme Wetting Substrate through Vacuum-Based Droplet Manipulation Heetak Han, Jung Seung Lee, Hyunchul Kim, Sera Shin, Jaehong Lee, Jongchan Kim, Xu Hou, Seung-Woo Cho, Jungmok Seo,,#,* and Taeyoon Lee,* School of Electrical and Electronic Engineering, Yonsei University, Seoul, 03722, Republic of Korea Department of Biotechnology, Yonsei University, Seoul, 03722, Republic of Korea Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, 48109, USA College of Chemistry and Chemical Engineering, Collaborative Innovation Center of Chem istry for Energy Materials, and State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, , China Center for Biomaterials, Biomedical Research Institute, Korea Institute of Science and Tech nology (KIST), Seoul, 02792, Republic of Korea # Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology (UST), Seoul, 02792, Republic of Korea *Address correspondence to jungmokseo@kist.re.kr, taeyoon.lee@yonsei.ac.kr

2 Wetting stability of the SPO/ SPI-layer-coated PDMS substrate. To examine the wetting stability of the coating upon stretching, the water contact angle (WCA) of the three types of coatings (SPO, SPI, and SPI with GL reagent) was determined at a 50% static strain (Figure S11). The SPO PDMS substrate exhibited a stable WCA greater than 150 without noticeable changes up to 24 h. In contrast, the SPI PDMS substrate, exhibited an extremely low WCA of 0 after the plasma treatment, which gradually increased to over 100 after 24 h. The increased WCA of the SPI PDMS over time is attributed to the migration of the lower molecular weight species from the organic ingredients of the substrate, such as bonding material and bulk PDMS. 1,2 Interestingly, when the glucose (GL) reagent solution was coated onto the SPI pattern following the plasma treatment, the WCA was maintained after storage. This permanent hydrophilization is attributed to hydrogen bonding between the protein in the GL reagent solution and the hydroxyl (-OH) groups on the substrate surface. 3 Evaporation time of the dispensed liquid droplet. The evaporation time (t e ) of the dispensed liquid droplet can be determined by size of the SPI pattern, as follows 4 : = ( ) (S1) where, is the density of the liquid, is the radius of the SPI pattern, is the contact angle of liquid droplet, D is the diffusion constant of vapor in air, n s is the density of the saturated vapor just above the liquid-air interface, and H is the relative humidity. According to the equation, the evaporation time rapidly increases as the radius of SPI pattern is increased. To examine the actual correlation between evaporation time and pattern size, various sizes of

3 droplets were dispensed onto the SPI patterns with dimeters ranging from 0.6 to 2.0 mm. The time required for the complete drying of the water droplets was determined using a video camera (room temperature and 75% relative humidity). As shown in Figure S14, the experimental results and the calculated results are in agreement. Furthermore, we confirm that the droplet evaporation time at the SPI pattern is sufficient for the completion of colorimetric reactions. 5,6

4 Figure S1. SPO layer coatings on various materials. Photographs of SPO layer coatings on a) metal, b) paper, c) plastic, and d) wood. The insets show the EG droplets on the SPO-coated surfaces. Scale bars: 2 cm. e) EG CAs on the SPO-layer-coated surfaces.

5 Figure S2. SPO-SPI patterned PDMS substrate after oxygen plasma treatment with a shadow mask.

6 Figure S3. Typical SEM images showing micro/nano hierarchical structures of the SPO layer a) before and b) after oxygen plasma treatment. Scale bars: 100 µm. There are no noticeable morphological changes after oxygen plasma treatment.

7 Figure S4. SAs of various liquid droplets on the SPO surfaces.

8 Figure S5. CAs and SAs of the various liquid droplets on the SPO substrate. Liquid droplets with various surface tensions were prepared by mixing deionized water (72 mn/m) and ethanol (21.8 mn/m) with different mixing ratios. The green region indicates the limit of liquid repellency.

9 Figure S6. Typical SEM images showing morphologies of the spray coated layer a) adhesive only and b) F-NPs only. Scale bars: 100 µm. The inset shows a higher-magnification image. Scale bar: 1 µm. Many nanopores containing tiny air pockets were formed by the agglomerated F-NPs after spray-coating.

10 Figure S7. Wettability of a) bare, b) fluorinated, and c) plasma treated-fluorinated SiO 2 surfaces. The CAs of the water droplets decreased to almost zero after the O 2 plasma treatment.

11 Figure S8. Typical SEM images of an SPO PDMS substrate after 1,000 cycles of stretching with a 100% strain. Scale bar: 200 µm. No noticeable damage (delamination or cracking of the SPO layer) was observed after 1,000 stretching cycles.

12 Figure S9. Instability of the droplet meniscus. Sequential photographs of a water droplet with increasing volume on a tilted SPO-SPI patterned PDMS substrate. The red dashed line indicates the angle between the upper meniscus of the water droplet and the substrate. With increasing volume of the water droplet, the upper meniscus became unstable due to gravitational forces.

13 Figure S10. Optical image of a circularly patterned shadow mask with different diameters ranging from 0.2 to 2.0 mm, and the corresponding SPI patterns on the SPO substrate.

14 Figure S11. a) WCAs of droplets on the three types of coatings (SPO, SPI, and SPI with GL reagent) with different storage times. b) Optical images of water droplets on the three coatings at various storage times.

15 Figure S12. a) Color intensity changes of the colorimetric GL assay using the SPO-SPI patterned PDMS substrate with different storage times (1, 3, 5, 7, and 14 days) and temperatures (room temperature and refrigerator). The color intensity changes after 1 day were considered to be the reference point. b) Photographs of the colorimetric assay results where a stable colorimetric response was observed.

16 Figure S13. Photograph of the droplet manipulation system with the SPO-SPI patterned PDMS substrate.

17 Calculated result Experimental result Figure S14. Theoretically calculated evaporation time (black line) and observed (red dot and line) evaporation time of the dispensed droplets on different SPI pattern diameters.

18 Figure S15. Mass loss of the water droplet on the SPO PDMS substrate. The mass loss rate is ~0.01 mg/s, which is negligible and did not affect the colorimetric assay results.

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