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. An electrochemical sensor with a 3D nanostructured working electrode surface is designed to enable precise in situ glucose measurement. A differential structure is proposed to eliminate the effect of passive perspiration, which leads to inaccurate blood glucose prediction. Fabrications of the epidermal biomicrofluidic device including formation of flexible electrodes, nanomaterial modification, and enzyme immobilization are fully realized by inkjet printing to enable facile manufacturing with low cost, which benefits practical production.

In recent years, DNA-based biosensors have shown great potential as the candidate of the next generation biomedical detection device due to their robust chemical properties and customizable biosensing functions. Compared with the conventional biosensors, the DNA-based biosensors have advantages such as wider detection targets, more durable lifetime, and lower production cost. Additionally, the ingenious DNA structures can control the signal conduction near the biosensor surface, which could significantly improve the performance of biosensors. In order to show a big picture of the DNA biosensor’s advantages, this article reviews the background knowledge and recent advances of DNA-based biosensors, including the functional DNA strands-based biosensors, DNA hybridization-based biosensors, and DNA templated biosensors. Then, the challenges and future directions of DNA-based biosensors are discussed and proposed.

An additive method using inkjet-printed silver nanoparticles to fabricate a microelectrode-based biosensor inside microchannels of PDMS with MPTMS modification is proposed.

Flexible fiber-shaped strain sensors show tremendous potential in wearable health monitoring and human‒machine interactions due to their compatibility with everyday clothing. However, the conductive and sensitive materials generated by traditional manufacturing methods to fabricate fiber-shaped strain sensors, including sequential coating and solution extrusion, exhibit limited stretchability, resulting in a limited stretch range and potential interface delamination. To address this issue, we fabricate a fiber-shaped flexible capacitive strain sensor (FSFCSS) by direct ink writing technology. Through this technology, we print parallel helical Ag electrodes on the surface of TPU tube fibers and encapsulate them with a high dielectric material BTO@Ecoflex, endowing FSFCSS with excellent dual-mode sensing performance. The FSFCSS can sense dual-model strain, namely, axial tensile strain and radial expansion strain. For axial tensile strain sensing, FSFCSS exhibits a wide detection range of 178%, a significant sensitivity of 0.924, a low detection limit of 0.6%, a low hysteresis coefficient of 1.44%, and outstanding mechanical stability. For radial expansion strain sensing, FSFCSS demonstrates a sensitivity of 0.00086 mmHg⁻¹ and exhibits excellent responsiveness to static and dynamic expansion strain. Furthermore, FSFCSS was combined with a portable data acquisition circuit board for the acquisition of physiological signals and human‒machine interaction in a wearable wireless sensing system. To measure blood pressure and heart rate, FSFCSS was combined with a printed RF coil in series to fabricate a wireless hemodynamic sensor. This work enables simultaneous application in wearable and implantable health monitoring, thereby advancing the development of smart textiles.

A novel cylindrical flexible enzyme-electrode sensor was fabricated with a bigger working electrode (WE) surface than the traditional pin-like one for implantable continuous glucose monitoring. On the WE surface, a 3D nanostructure consisting of graphene and platinum nanoparticles was constructed to enhance the sensitivity; in conjunction with the bigger WE, this nanostructure enabled hypoglycemia detection, which is still a big challenge in clinics. The cylindrical sensor was fabricated by rotated inkjet printing which enabled direct patterning of microstructures on a curved surface, thus overcoming the restriction of the traditional planar micromachining by photolithography. Specifically, the cylindrical substrate (polyetheretherketone, PEEK) was modified by (3-aminopropyl) trimethoxysilane and (3-mercaptopropyl) trimethoxysilane to facilitate surface wettability, which discourages the coalescence of adjacent droplets, and to facilitate the adhesion of metals to PEEK in order to construct robust electrodes. A synchronous heating method was used to evaporate the solvent of the droplets quickly to prevent them from running along the cylindrical surface, which affects the formation of the printed electrode significantly. In vitro experimental results showed that the proposed sensor was able to detect the glucose concentration ranging from 0 to 570 mg dL⁻¹ which demonstrated its capability for physiological glucose detection. In vivo experiments were conducted with rats, and the measurement results recorded using the implanted cylindrical sensor showed great compliance to those recorded using a commercial glucometer which exhibited the viability of the proposed sensor for implantable continuous glucose monitoring, even under the hypoglycemic conditions.