Highly Stretchable Potentiometric pH Sensor Fabricated via Laser Carbonization and Machining of Carbon−Polyaniline Composite

Abstract

The development of stretchable sensors has recently attracted considerable attention. These sensors have been used in wearable and robotics applications, such as personalized health-monitoring, motion detection, and human-machine interfaces. Herein, we report on a highly stretchable electrochemical pH sensor for wearable point-of-care applications that consists of a pH-sensitive working electrode and a liquid-junction-free reference electrode, in which the stretchable conductive interconnections are fabricated by laser carbonizing and micromachining of a polyimide sheet bonded to an Ecoflex substrate. This method produces highly porous carbonized 2D serpentine traces that are subsequently permeated with polyaniline (PANI) as the conductive filler, binding material, and pH-sensitive membrane. The experimental and simulation results demonstrate that the stretchable serpentine PANI/C-PI interconnections with an optimal trace width of 0.3 mm can withstand elongations of up to 135% and are robust to more than 12 000 stretch-and-release cycles at 20% strain without noticeable change in the resistance. The pH sensor displays a linear sensitivity of -53 mV/pH (r = 0.976) with stable performance in the physiological range of pH 4-10. The sensor shows excellent stability to applied longitudinal and transverse strains up to 100% in different pH buffer solutions with a minimal deviation of less than ±4 mV. The material biocompatibility is confirmed with NIH 3T3 fibroblast cells via PrestoBlue assays.

Flexible and Robust Electro‐Optically Responsive Films Based on Novel Silica/Oligoaniline/Carbon Dots Composite

“…[1][2][3][4] Organic semiconductors, especially those based on conjugated polymers, are promising towards these ends and have been explored extensively. [5][6][7][8] While these materials offer extraordinary properties, production scale manufacturing of devices based on many of these materials remains a chemistry and engineering challenge due to a variety of factors. One issue relates to making large, even, and defect free films on transparent electrodes that are sufficient for device applications.…”

Stretchable sensors for environmental monitoring

“…Because of the straightforward transduction principle and simple readout configuration, potentiometric pH sensors have been the dominant instrument used for pH sensing, including stretchable pH sensors. 112,121,188 The spectrometric pH sensor is an alternative sensing technique. Unlike electrochemical pH sensing, the spectrometric technique indirectly acquires the pH of a solution by measuring the concentration of the acidic and basic forms of the pH indicators.…”

“…Non-stretchable ISE materials were optimized through geometry engineering into meander/serpentine patterns and island-bridge configurations to produce stretchable pH sensors. 121,188 In 2014, Chung et al reported an island-bridge strategy enabled stretchable pH sensor array. 191 In 2015, Hwang et al reported the production of stretchable Si NM-and Si NR-based transient electronics with device islands connected by serpentine or out-out-plane interconnects that allow the system to accommodate large deformations without fracture.…”

“…In 2017, Rahimi et al introduced a low-cost technique to fabricate a highly stretchable electrochemical pH sensor. 188 The stretchable conductive interconnection consists of porous carbonized 2D serpentine traces fabricated by direct laser carbonizing and micromachining of a PI sheet bonded to an Ecoflex substrate [ Fig. 7(b)].…”

Microcontact Printing with Laser Direct Writing Carbonization for Facile Fabrication of Carbon‐Based Ultrathin Disk Arrays and Ordered Holey Films

“…[3] With a soft polymer, to the traditionally adopted direct heating method for polymer carbonization lie on its patternability in ambient environment with more flexibility, versatility, and highly controlled fashion. DLWc has been successfully applied to fabricate carbon patterns targeted for a variety of interesting applications, e.g., supercapacitors, [37][38][39][40][41] flexible electrodes, [42] heating elements, [43] various sensors for detecting/measuring sound and vibration, [39] strain or stress, [44][45][46] humidity, [46] pH value, [47] and biomolecules. [48] Given the success of DLWc, its use for fabricating dense, homogenous, and ultrathin carbon films is still a challenge.…”