title: Stretchable, multiplexed pH sensors with demonstrations on rabbit and human hearts undergoing ischemia.
abstract: Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces, and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrOx pH sensors encapsulated in thin, low-modulus elastomers to yield conformal monitoring systems capable of noninvasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In vitro testing reveals super-Nernstian sensitivity with excellent uniformity (69.9 ± 2.2 mV/pH), linear response to temperature (-1.6 mV °C(-1) ), and minimal influence of extracellular ions (<3.5 mV). Device examples include sensor arrays on balloon catheters and on skin-like stretchable membranes. Real-time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia-reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long-term implants.
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 2V4, Canada; Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Hyun-Joong
authors.initials: HJ
authors.lastname: Chung
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Sulkin
authors.forename: Jong-Seon
authors.initials: JS
authors.lastname: Kim
authors.forename: Camille
authors.initials: C
authors.lastname: Goudeseune
authors.forename: Hsin-Yun
authors.initials: HY
authors.lastname: Chao
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Song
authors.forename: Sang Yoon
authors.initials: SY
authors.lastname: Yang
authors.forename: Yung-Yu
authors.initials: YY
authors.lastname: Hsu
authors.forename: Roozbeh
authors.initials: R
authors.lastname: Ghaffari
authors.forename: Igor R
authors.initials: IR
authors.lastname: Efimov
authors.forename: John A
authors.initials: JA
authors.lastname: Rogers
mesh_terms: D000818:Animals; D006328:Cardiac Catheterization; D004581:Electronics; D004867:Equipment Design; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry / Q000378:metabolism; D007511:Ischemia / Q000378:metabolism / Q000473:pathology; D008839:Microelectrodes; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism*; D019736:Prostheses and Implants; D011817:Rabbits; D015424:Reperfusion; D013696:Temperature
chemical_list: D007477:Ions
keywords: heart ischemia; microfabrication; pH sensor; spatiotemporal mapping; stretchable electronics