Supplementary Information for Printable Ultrathin Metal Oxide ...
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, 2Department 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, 4Department 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: [email protected] (Y. S. R.) and [email protected] (H.-R. T.)
Figure S1. Transfer characteristics of liquid-gated In2O3 FETs showing that the leakage current between the liquid electrolyte (red) and the gate electrode is negligible.
Figure S2. Cyclic voltammetry of a Pt foil in 0.1× PBS with (blue: CG = 1 mM, red: CG = 100 µM) or without (black) glucose.
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 y0 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, y0, is calculated from:
where EPI, EMO, hPI, and hmo 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:
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=θ0. Here, R, r0, d, E, and γ, are 837 µm, 7.9 µm, 810 µm, 2.55 GPa, and 10 mJ/m2 respectively.
Based on the above information, we can define three different cases for the contact condition. First, when γ is small, then γc leads to non-conformal contact. The second case is partial conformal contact where γ is between γc and γc'. Third, once γ starts to become larger than γc', 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
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, 2Department 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, 4Department 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: [email protected] (Y. S. R.) and [email protected] (H.-R. T.)
Figure S1. Transfer characteristics of liquid-gated In2O3 FETs showing that the leakage current between the liquid electrolyte (red) and the gate electrode is negligible.
Figure S2. Cyclic voltammetry of a Pt foil in 0.1× PBS with (blue: CG = 1 mM, red: CG = 100 µM) or without (black) glucose.
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 y0 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, y0, is calculated from:
where EPI, EMO, hPI, and hmo 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:
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=θ0. Here, R, r0, d, E, and γ, are 837 µm, 7.9 µm, 810 µm, 2.55 GPa, and 10 mJ/m2 respectively.
Based on the above information, we can define three different cases for the contact condition. First, when γ is small, then γc leads to non-conformal contact. The second case is partial conformal contact where γ is between γc and γc'. Third, once γ starts to become larger than γc', 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
