Ten years of laser-induced graphene: impact and future prospect on biomedical, healthcare, and wearable technology.

Since its introduction in 2014, laser-induced graphene (LIG) from commercial polymers has been gaining interests in both academic and industrial sectors. This can be clearly seen from its mass adoption in various fields ranging from energy storage and sensing platforms to biomedical applications. LIG is a 3-dimensional, nanoporous graphene structure with highly tuneable electrical, physical, and chemical properties. LIG can be easily produced by single-step laser scribing at normal room temperature and pressure using easily accessible commercial level laser machines and materials. With the increasing demand for novel wearable devices for biomedical applications, LIG on flexible substrates can readily serve as a technological platform to be further developed for biomedical applications such as point-of-care (POC) testing and wearable devices for healthcare monitoring system. This review will provide a comprehensive grounding on LIG from its inception and fabrication mechanism to the characterization of its key functional properties. The exploration of biomedicals applications in the form of wearable and point-of-care devices will then be presented. Issue of health risk from accidental exposure to LIG will be covered. Then LIG-based wearable devices will be compared to devices of different materials. Finally, we discuss the implementation of Internet of Medical Things (IoMT) to wearable devices and explore and speculate on its potentials and challenges.

Basic Guide to Multilayer Microfluidic Fabrication with Polyimide Tape and Diode Laser.

For normal operations, microfluidic devices typically require an external source of pressure to deliver fluid flow through the microchannel. This requirement limits their use for benchtop research activities in a controlled static environment. To exploit the full potential of the miniaturization and portability of microfluidic platforms, passively driven capillary microfluidic devices have been developed to completely remove the need for an external pressure source. Capillary microfluidics can be designed to perform complex tasks by designing individual components of the device. These components, such as the stop valve and trigger valve, operate through changes in microchannel dimensions and aspect ratios. A direct, maskless fabrication protocol that allows the precise fabrication of microchannels and other microfluidic components is introduced here. A diode laser and polyimide tape on a PMMA substrate are the only components needed to start fabrication. By varying the laser power used and the number of laser repetitions, various depths and widths of the microchannel can be quickly created to meet specific needs. As an example of a functional unit, a trigger valve was fabricated and tested, as proof of the validity of the fabrication protocol.

Diode Laser and Polyimide Tape Enables Cheap and Fast Fabrication of Flexible Microfluidic Sensing Devices.

Wearable devices are a new class of healthcare monitoring devices designed for use in close contact with the patient's body. Such devices must be flexible to follow the contours of human anatomy. With numerous potential applications, a wide variety of flexible wearable devices have been created, taking various forms and functions. Therefore, different fabrication techniques and materials are employed, resulting in fragmentation of the list of equipment and materials needed to make different devices. This study attempted to simplify and streamline the fabrication process of all key components, including microfluidic chip and flexible electrode units. A combination of diode laser CNC machine and polyimide tape is used to fabricate flexible microfluidic chip and laser-induced graphene (LIG) electrodes, to create flexible microfluidic sensing devices. Laser ablation on polyimide tape can directly create microfluidic features on either PDMS substrates or LIG electrodes. The two components can be assembled to form a flexible microfluidic sensing device that can perform basic electrochemical analysis and conform to curved surfaces while undergoing microfluidic flow. This study has shown that simple, commonly available equipment and materials can be used to fabricate flexible microfluidic sensing devices quickly and easily, which is highly suitable for rapid prototyping of wearable devices.

Sustainable and Efficient: A Reusable DIY Three-Electrode Base Plate for Microfluidic Electroanalysis and Biosensing.

A sustainable three-electrode platform for affordable microfluidic electroanalysis is described. The device can be handmade using common tools and, facilitating broad applicability, is indefinitely reusable through simple surface polishing. Compact prototypes with Pt counter, Pt working, and Ag/AgCl reference electrode disks were combined with silicone lid plates containing a microchannel for electrolyte flow. Redox voltammetry/amperometry of excellent quality was achieved in static and flowing ferricyanide solutions, respectively. Modified with a glucose oxidase surface layer, base plate Pt WEs performed very well as amperometric biosensors for microfluidic blood glucose testing. The electrode system is recyclable, compatible with matching lid plate microchannels, and functionally adaptable regarding the constituent metal and electrode surface modifications. This asset combination makes the device a sustainable detection tool for microfluidic electroanalysis, with applications ranging from direct detection of redox-active analytes to bioreceptor-assisted biosensing. It avoids costly microfabrication with clean-room use, and the accessibility of microfluidic EC (bio)sensing is thus greatly increased, especially for users with restricted budgets.

Rapid sub-micromolar amperometric enzyme biosensing with free substrate access but without nanomaterial signalling support: oxidase-based glucose detection as a proof-of-principle example.

High-sensitivity electrochemical glucose biosensing has so far been possible only through incorporation of nanomaterials into the glucose oxidase-(GOx) containing polymer layer on the detector surface. Here, as a conceptionally novel simplified option, pure gelatin thin films with covalently attached GOx were used to convert platinum (Pt) disk electrodes into rapidly responding amperometric glucose probes with a sub-micromolar limit of detection. The advanced enzymatic tools are easy to make and, as is crucial for a focus on waste minimization, green and sustainable, through restriction of sensor modification to readily available economical materials.