Carbon Nanotube Chemiresistor for Wireless pH Sensing

Abstract

The ability to accurately measure real-time pH fluctuations in-vivo could be highly advantageous. Early detection and potential prevention of bacteria colonization of surgical implants can be accomplished by monitoring associated acidosis. However, conventional glass membrane or ion-selective field-effect transistor (ISFET) pH sensing technologies both require a reference electrode which may suffer from leakage of electrolytes and potential contamination. Herein, we describe a solid-state sensor based on oxidized single-walled carbon nanotubes (ox-SWNTs) functionalized with the conductive polymer poly(1-aminoanthracene) (PAA). This device had a Nernstian response over a wide pH range (2–12) and retained sensitivity over 120 days. The sensor was also attached to a passively-powered radio-frequency identification (RFID) tag which transmits pH data through simulated skin. This battery-less, reference electrode free, wirelessly transmitting sensor platform shows potential for biomedical applications as an implantable sensor, adjacent to surgical implants detecting for infection.

Cross-Point Resistive Switching Memory and Urea Sensing by Using Annealed GdOxFilm in IrOx/GdOx/W Structure for Biomedical Applications

“…Considering the smallest drift, a lower detection of pH change is found to be 0.034 (i.e., drift/sensitivity = 1.8/53.2), which is similar to the reported value of detection limit (0.04). 53 To improve the sensing of bio-analyte, a new application of resistive switching memory has been demonstrated for the first time (Figure 1a). Due to high pH sensitivity of the annealed GdO x films, the cross-point memory after annealing treatment has been performed for urea sensing.…”

A Highly Miniaturized Low-Power CMOS-Based pH Monitoring Platform

“…Recently, there have been reports of the implementation of fully-integrated pH sensing systems [20]- [22], however the large size of the final packaged device will prove to be a challenge in vivo as it has been shown that device size and degree of tissue trauma dictate the magnitude of both chronic and acute inflammation [23], [24]. Recent advancements in implantable powering schemes, including advanced high-efficiency miniature battery design as well as localized electromagnetic powering, present the ability to drive low-technology node analog and mixedsignal fabricated integrated circuits (ICs) utilized for analyte detection and signal conditioning [25], [26].…”

Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique

“…Research studies have attempted to detect pH in the following areas: potentiometric [12], micro-electro-mechanical systems (MEMS) [13], capacitive [14], surface acoustic waves [15], complementary metal–oxide–semiconductor (CMOS) [16], carbon nanotubes [17,18], chemiresistors [19,20], red green blue (RGB) colors array [21], fluorescent [22], surface plasmon resonance (SPR) [23,24], localized surface plasmon resonance (LSPR) [25,26], etc. …”