Printable Ultrathin Metal Oxide Semiconductor-Based Conformal Biosensors

Transcription

1 Supplementary Information for Printable Ultrathin Metal Oxide Semiconductor-Based Conformal Biosensors You Seung Rim, *,1,2,# Sang-Hoon Bae, 1,2,# Huajun Chen, 1,2 Jonathan L. Yang, 1,3 Jaemyung Kim, 1,4 Anne M. Andrews, 4,5 Paul S. Weiss, 1,2,4 Yang Yang, 1,2 and Hsian-Rong Tseng *,1,3 1 California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States, 2 Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States, 3 Department of Pharmacology, University of California, Los Angeles, Los Angeles, California 90095, United States, 4 Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States, and 5 Department of Psychiatry, Hatos Center for Neuropharmacology, and Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, California 90095, United States. *To whom correspondence should be addressed: ysrim79@ucla.edu (Y. S. R.) and hrtseng@mednet.ucla.edu (H.-R. T.)

2 Figure S1. Transfer characteristics of liquid-gated In 2 O 3 FETs showing that the leakage current between the liquid electrolyte (red) and the gate electrode is negligible.

3 Figure S2. Cyclic voltammetry of a Pt foil in 0.1 PBS with (blue: C G = 1 mm, red: C G = 100 µm) or without (black) glucose.

4 Stiffness and adhesion energy calculations for determining conformal contact To study the critical thickness needed to achieve conformal contact between the devices fabricated here and artificial PDMS rough substrates, which mimic human skin surface contours, we began with stiffness calculations. Stiffness values can be calculated using the following equation: where E, b, h, and y 0 are Young s modulus, device width, device thickness, and the distance between the neutral plane and the bottom, respectively. The distance between the neutral plane and the bottom, y 0, is calculated from: where E PI, E MO, h PI, and h mo are the Young s modulus of the PI film, the Young s modulus of the metal oxide layer, the height of the PI film, and the height of the metal oxide layer, respectively. For the critical adhesion energy, we built up a two-cylinder model based on the surface profile (Figure 3a). The total energy for the wrapped state is: In addition, the bending energy is:

5 The adhesion energy is: Here, the contact angle of the device with one cylinder, θ, for the overlapped cylinder model can be expressed as: The adhesion energy has a minimum value when θ=θ 0. Here, R, r 0, d, E, and γ, are 837 µm, 7.9 µm, 810 µm, 2.55 GPa, and 10 mj/m 2 respectively. Based on the above information, we can define three different cases for the contact condition. First, when γ is small, then γ c leads to non-conformal contact. The second case is partial conformal contact where γ is between γ c and γ c '. Third, once γ starts to become larger than γ c ', complete conformal contact occurs where: From the numerical modeling, the calculated critical thickness of the devices investigated here is 1.77 µm. Thus, these devices can begin to make conformal contact with the target surface at thicknesses <1.77 µm.

6 Figure S3. (a) Surface profile information of the artificial PDMS skin replicas was measured by using a surface profiler. (b) Schematic illustration of the two-cylinder model used to calculate the adhesion energy between a device and a target surface.

7 Strain calculation of ultrathin In 2 O 3 film on artificial PDMS skin replicas To evaluate the flexibility of the In 2 O 3 -based biosensors, we carried out mechanical strain calculations for the In 2 O 3 films on artificial PDMS skin replicas. For these calculations, we assumed that the overall bending radius of the devices on artificial PDMS skin replicas was approximately 837 µm using the surface profile information (Figure S3a). Since the In 2 O 3 films are expected to suffer the highest strain due to the high Young s modulus under bending, we only considered the strain of the In 2 O 3 films themselves. = + 2 (1+2 + ) (1+ )(1+ ), = and = where d s, d f, R, Y s, and Y f are the thickness of the In 2 O 3 film, the thickness of the PI film, the bending radius, the Young s modulus of the In 2 O 3 film, and the Young s modulus of the PI film, respectively. The d s and d f are 3.5 nm and 1.5 um and the Young s modulus of the In 2 O 3 and PI films are approximately GPa and 3.2 GPa, respectively. 1-4 The calculated strain value of the In 2 O 3 film is thus 0.078~0.082%. Typically, the electrical and structural properties of In-base oxide films do not change at the strain of below 1% Thus, these values of the In 2 O 3 film do not affect the electrical degradation of In 2 O 3 films even at a small bending radius of below 1 mm.

8 Figure S4. Representative trace of the change in normalized current response of an In 2 O 3 FET-based biosensor with respect to time following an abrupt ph change. Current values for sensing purposes are measured when the response magnitude has saturated (become stable) at each ph value.

9 Figure S5. (a) Representative trace of the response of an In 2 O 3 FET-based biosensor without APTES silanization as a function of ph. (b) Average response values of these devices with respect to ph. Five devices were tested. Error bars represent the standard deviations of the means.

10 Figure S6. Representative responses of In 2 O 3 sensors to physiologically relevant D-glucose concentrations. Similar L-glucose concentrations were tested to investigate the specificity of the sensor responses. References 1. Bartolome, J.; Hidalgo, P.; Maestre, D.; Cremades, A.; Piqueras, J. In-SituScanning Electron Microscopy and Atomic Force Microscopy Young's Modulus Determination of Indium Oxide Microrods for Micromechanical Resonator Applications. Appl. Phys. Lett. 2014, 104, IFukuhara, M.; Sampei, A. Temperature Dependence of Elastic Moduli and Internal Dilational and Shear Frictions of Polyimide. J. Polym. Sci., Part B: Polym. Phys. 1996, 34, Yoshikawa, T.; Yagi, T.; Oka, N.; Jia, J. J.; Yamashita, Y.; Hattori, K.; Seino, Y.; Taketoshi, N.; Baba, T.; Shigesato, Y. Thermal Conductivity of Amorphous Indium- Gallium-Zinc Oxide Thin Films. Appl. Phys. Express 2013, Zhang, K. H. L.; Lazarov, V. K.; Veal, T. D.; Oropeza, F. E.; McConville, C. F.; Egdell, R. G.; Walsh, A. Thickness Dependence of the Strain, Band Gap and Transport Properties of Epitaxial In 2 O 3 Thin Films Grown on Y-Stabilised ZrO 2 (111). J. Phys. Condens. Matter 2011, 23,

11 5. Sharma, B. K.; Jang, B.; Lee, J. E.; Bae, S. H.; Kim, T. W.; Lee, H. J.; Kim, J. H.; Ahn, J. H. Load-Controlled Roll Transfer of Oxide Transistors for Stretchable Electronics. Adv. Funct. Mater. 2013, 23, Chen, Z.; Cotterell, B.; Wang, W. The Fracture of Brittle Thin Films on Compliant Substrates in Flexible Displays. Eng. Fract. Mech. 2002, 69, Kwak, K.; Cho, K.; Kim, S. Stable Bending Performance of Flexible Organic Light- Emitting Diodes Using IZO Anodes. Sci. Rep. 2013, Lin, C. Y.; Chien, C. W.; Wu, C. C.; Yeh, Y. H.; Cheng, C. C.; Lai, C. M.; Yu, M. J.; Leu, C. M.; Lee, T. M. Effects of Mechanical Strains on the Characteristics of Top-Gate Staggered a-igzo Thin-Film Transistors Fabricated on Polyimide-Based Nanocomposite Substrates. IEEE Trans. Electron Device 2012, 59, Cantarella, G.; Munzenrieder, N.; Petti, L.; Vogt, C.; Buthe, L.; Salvatore, G. A.; Daus, A.; Troster, G. Flexible In-Ga-Zn-O Thin-Film Transistors on Elastomeric Substrate Bent to 2.3% Strain. IEEE Electron Device Lett. 2015, 36, Chen, Z.; Cotterell, B.; Wang, W.; Guenther, E.; Chua, S. J. A Mechanical Assessment of Flexible Optoelectronic Devices. Thin Solid Films 2001, 394,