Streaming Current Based Microtubular Enzymatic Sensor for Self‐Powered Detection of Urea

Abstract

The emergence of microfluidic techniques coupled with flow‐induced electrification has advanced the development of innovative self‐powered sensors. However, selective detection of target substances using these sensors is extremely challenging, owing to the lack of recognition elements in the flow pathway. To overcome this, catalytic enzymes are immobilized on the microfluidic channel and the concentration of targets is measured via monitoring the streaming current. As an example, a urease equipped self‐powered microtubular sensor is developed to selectively detect urea, a physiologically and industrially important molecule. The urease catalyzes the hydrolysis of urea into ions, increasing the pH of the fluid, which serves as the basis of the sensing mechanism. Remarkably, high sensitivity, wide detection range, short response time, and superior selectivity are reported for urinary urea detection. The accuracy and reliability of sensing in artificial urine are validated with the standard spectrophotometric method. The microtubular sensor features facile fabrication and operation and circumvents the need for sophisticated peripherals, highlighting its enormous potential in chemical and biomedical applications, such as pollutant detection, food quality assessment, disease diagnosis, and point‐of‐care testing.

Flexible Hybrid Sensors for Health Monitoring: Materials and Mechanisms to Render Wearability

“…Our group has recently reported a self-powered chemical sensor that can detect urea with high sensitivity and selectivity. [213] Streaming current as the measurable electrical signal was generated by continuously infusing the solution through the microtubular channel of the sensor. Meanwhile, the hydrolysis of urea was catalyzed by the urease immobilized on the channel surface.…”

Whispering Gallery Mode Optical Microresonators: Structures and Sensing Applications

“…In 2018, Yu et al. proposed a microtubule enzyme sensor (μTES) that can selectively detect self‐supplied current flow of noncharged species, as shown in Figure c, and used urease as the recognition element to selectively detect urea in the microtubular . This simple and effective sensing technology had great potential in the next generation of biochemical sensors.…”

“…c) 3D schematic of the sensor, comprising a PDMS microtube, an ammeter, and a syringe pump (pump not shown). Reproduced with permission . Copyright 2018, Wiley‐VCH Verlag GmbH and Co. KGaA.…”

Surface Potential/Charge Sensing Techniques and Applications

“…Li et al [3] designed a DNA detection system based on DNA-PNA hybridization inside a microchannel, measured with a streaming potential analyzer, and obtained a detection limit of 10 nM. Yu et al [114] developed a self-powered urea sensor by immobilizing catalytic enzymes on the microfluidic channel. The fluid pH increased when hydrolyzing urea into ions, which changed the measured streaming current.…”

“…(a) A schematic setup (top) and characterization of surface treatment to silicon nitride surface (bottom)[109]; (b) schematic of urea hydrolysis catalyzed by the urease immobilized on microtube wall (top), and current output increases with increasing urea concentration from 0.0-10.0 mM (red line). The current output is independent of urea concentration without urea (blue line)[114]; (c) AFM (scan width 20 µm) of latex particle monolayers on mica (top), and the zeta potential at different MgCl 2 concentration (bottom)[113]; (d) schematic diagram of a plug for detecting hydroxyapatite particles with flow potential (top), and relationship between the zeta potential and KCl ion concentrations (bottom)[115].…”