A flexible glucose biosensor modified by reduced-swelling and conductive zwitterionic hydrogel enzyme membrane.

This paper reports a flexible glucose biosensor which is modified by a reduced-swelling and conductive zwitterionic hydrogel enzyme membrane that contains two forms of chemical cross-links. One chemical cross-linking is induced by thermal initiators and forms the basal network of the hydrogel. Another cross-linking is achieved by the coordination interactions between the multivalent metal ion Al and anionic group -COO of zwitterionic poly-carboxy betaine (pCBMA), which significantly increase the cross-linking density of the zwitterionic hydrogel, improving the reduced-swelling property and reducing the pore size.

A wearable microfluidic system for efficient sweat collection and real-time detection.

Sweat is an important biofluid with rich physiological information that can evaluate human health condition. Wearable sweat sensors have received widespread attention in recent years due to the benefits of non-invasive, continuous, and real-time monitoring. Currently, an efficient device integrating sweat collection and detection is still needed.

An inkjet-printed bendable antenna for wearable electronics.

104Flexible antennas, which can conform to the skin and transfer signals to terminals, are particularly useful for wearable electronics. Bending, which frequently occurs to flexible devices, significantly affects the performance of flexible antennas. Inkjet printing has been used as an additive manufacturing technology for fabricating flexible antenna in recent years.

Effect of interstitial fluid pH on transdermal glucose extraction by reverse iontophoresis.

Reverse iontophoresis (RI) is a promising technology in the field of continuous glucose monitoring (CGM), offering significant advantages such as finger-stick-free operation, wearability, and non-invasiveness. In the glucose extraction process based on RI, the pH of the interstitial fluid (ISF) is a critical factor that needs further investigation, as it directly influences the accuracy of transdermal glucose monitoring. In this study, a theoretical analysis was conducted to investigate the mechanism by which pH affects the glucose extraction flux.

Electrically Inspired Flexible Electrochemical Film Power Supply for Long-Term Epidermal Sensors.

This paper, for the first time, reports an electrically inspired flexible electrochemical film power supply for long-term epidermal sensors. This device can periodically provide electrical power for several hours after a short-time electrical activation. The electrical activation makes acetylcholine, which is infused into the subcutaneous tissue by iontophoresis.

Flexible organic field-effect transistors-based biosensors: progress and perspectives.

Organic field-effect transistors (OFETs) have been proposed beyond three decades while becoming a research hotspot again in recent years because of the fast development of flexible electronics. Many novel flexible OFETs-based devices have been reported in these years. Among these devices, flexible OFETs-based sensors made great strides because of the extraordinary sensing capability of FET.

Reverse iontophoresis with the development of flexible electronics: A review.

Skin-centric diagnosis techniques, such as epidermal physiological parameter monitoring, have developed rapidly in recent years. The analysis of interstitial fluid (ISF), a body liquid with abundant physiological information, is a promising method to obtain health status because ISF is easily assessed by implanted or percutaneous measurements. Reverse iontophoresis extracts ISF by applying an electric field onto the skin, and it is a promising method to noninvasively obtain ISF, which, in turn, enables noninvasive epidermal physiological parameter monitoring.

A thermal activated and differential self-calibrated flexible epidermal biomicrofluidic device for wearable accurate blood glucose monitoring.

This paper reports a flexible electronics-based epidermal biomicrofluidics technique for clinical continuous blood glucose monitoring, overcoming the drawback of the present wearables, unreliable measurements. A thermal activation method is proposed to improve the efficiency of transdermal interstitial fluid (ISF) extraction, enabling extraction with a low current density to notably reduce skin irritation. An Na sensor and a correction model are proposed to eliminate the effect of individual differences, which leads to fluctuations in the amount of ISF extraction.

Step emulsification in microfluidic droplet generation: mechanisms and structures.

The droplet-based microfluidic techniques have been applied widely in functional material synthesis and biomedical information measurements, wherein step emulsification as an integrated system combines the advantages of homogeneity and throughput in monodisperse droplet formation. This paper reviews the mechanisms and classical structures of step emulsification. In terms of droplet formation mechanisms, we describe the droplet size and detachment regimes related to the microchannel geometry.

Experimental investigation on the effects of the standoff distance and the initial radius on the dynamics of a single bubble near a rigid wall in an ultrasonic field.

Bubble behaviors near a boundary in an ultrasonic field are the fundamental forms of acoustic cavitation and of substantial importance in various applications, such as industry cleaning, chemical engineering and food processing. The effects of two important factors that strongly affect the dynamics of a single acoustic cavitation bubble, namely, the initial bubble radius and the standoff distance, were investigated in this work. The temporal evolution of the bubble was recorded using high speed microphotography.

Sticker Microfluidics: A Method for Fabrication of Customized Monolithic Microfluidics.

This paper proposes a novel strategy and an all-in-one toolbox that allows instrument-free customization of integrated microfluidic systems. Unlike the modular design of combining multiple microfluidic chips in the previous literature, this work, for the first time, proposes a "template sticker" method, in which sacrificial templates for microfluidic components are batch-produced in the form of standardized stickers and packaged into a toolbox. To create a customized monolithic microfluidic system, the end users only need to select and combine various template stickers following formulated steps.

Inkjet Pattern-Guided Liquid Templates on Superhydrophobic Substrates for Rapid Prototyping of Microfluidic Devices.

This paper presents a novel method of rapidly customizing microfluidic systems using a consumer-grade inkjet printer and a commercially available superhydrophobic spray. By casting polydimethylsiloxane (PDMS) on liquid templates that are defined by inkjet-printed hydrophilic patterns on superhydrophobically-coated PDMS substrates, microfluidic devices can be directly fabricated. Utilizing the interfacial properties of the superhydrophobic coating and the template liquid, the fabrication of microfluidics could be done with minimum effort and expertise, and unlike previously reported works, no mask and bonding process is necessary.

Effect of low-frequency ultrasonic field at different power on the dynamics of a single bubble near a rigid wall.

Various bubble dynamics near the boundary in an acoustic field play a significantly important role in destructive erosion which has been associated with applications in industry cleaning, chemical engineering and biomedicine. But the effect mechanism of the high pressure on the boundary induce by single acoustic cavitation bubble has not been fully elucidated, which is vital for further application. The objective of this paper is to investigate the behaviors of a gas bubble near a rigid wall in a low frequency ultrasonic field.

Flattened fiber-optic ATR sensor enhanced by silver nanoparticles for glucose measurement.

This paper proposes a novel fiber attenuated total reflection (ATR) sensor with silver nanoparticles (AgNPs) on the flattened structure based on mid-infrared spectroscopy for detecting low concentration of glucose with high precision. The flattened structure was designed to add the effective optical path length to improve the sensitivity. AgNPs were then deposited on the surface of the flattened area of the fiber via chemical silver mirror reaction for further improving the sensitivity by enhancing the infrared absorption.

From functional structure to packaging: full-printing fabrication of a microfluidic chip.

This paper presents a concept of a full-printing methodology aiming at convenient and fast fabrication of microfluidic devices. For the first time, we achieved a microfluidic biochemical sensor with all functional structures fabricated by inkjet printing, including electrodes, immobilized enzymes, microfluidic components and packaging. With the cost-effective and rapid process, this method provides the possibility of quick model validation of a novel lab-on-chip system.

A continuous glucose monitoring device by graphene modified electrochemical sensor in microfluidic system.

This paper presents a continuous glucose monitoring microsystem consisting of a three-electrode electrochemical sensor integrated into a microfluidic chip. The microfluidic chip, which was used to transdermally extract and collect subcutaneous interstitial fluid, was fabricated from five polydimethylsiloxane layers using micromolding techniques. The electrochemical sensor was integrated into the chip for continuous detection of glucose.