Evolution of Wearable Devices with Real-Time Disease Monitoring for Personalized Healthcare

Abstract

Wearable devices are becoming widespread in a wide range of applications, from healthcare to biomedical monitoring systems, which enable continuous measurement of critical biomarkers for medical diagnostics, physiological health monitoring and evaluation. Especially as the elderly population grows globally, various chronic and acute diseases become increasingly important, and the medical industry is changing dramatically due to the need for point-of-care (POC) diagnosis and real-time monitoring of long-term health conditions. Wearable devices have evolved gradually in the form of accessories, integrated clothing, body attachments and body inserts. Over the past few decades, the tremendous development of electronics, biocompatible materials and nanomaterials has resulted in the development of implantable devices that enable the diagnosis and prognosis through small sensors and biomedical devices, and greatly improve the quality and efficacy of medical services. This article summarizes the wearable devices that have been developed to date, and provides a review of their clinical applications. We will also discuss the technical barriers and challenges in the development of wearable devices, and discuss future prospects on wearable biosensors for prevention, personalized medicine and real-time health monitoring.

Keywords: attachable devices; biosensor; implantable devices; personal health; physiological signals; point-of-care; portable devices; real-time monitoring; wearable devices.

Figure 1

Industrial wearable technologies. (A) Evolution of wearable medical devices (B) Application of wearable devices in the healthcare and biomedical monitoring systems. Reproduced with permission from Hwang, I.; et al. Multifunctional smart skin adhesive patches for advanced health care; Wiley, 2018 [9] and Yao, H.; et al. A contact lens with embedded sensor for monitoring tear glucose level; Elsevier, 2011 [10].

Figure 2

Portable medical and healthcare devices worn on body parts.

Figure 3

Stretchable ultrasonic device to identify and capture arterial blood-pressure waveforms. The high-performance 1–3 composite with piezoelectric microrods embedded in an epoxy matrix suppresses shear vibration modes and improves ultrasonic penetration into the skin. The wearable device can monitor peripheral vessel hemodynamics at different locations, for example, to sites of the brachial, radial, femoral or dorsalis pedis arteries. Reproduced with permission from Wang, C.; et al. Monitoring of the central blood pressure waveform via a conformal ultrasonic device; Springer Nature, 2018 [61].

Figure 4

Flexible and stretchable sensing platforms. (A) Optical images of patch consisting of a humidity, glucose, pH, tremor, heater and temperature sensor. The diabetes patch is laminated on the human skin and is connected to a portable electrochemical analyzer with external devices via Bluetooth. Sweat glucose concentrations measured by the diabetes patch (red circles) and a commercial glucose assay kit (red dots) are well matched. In addition, changes in the sweat glucose concentration are well correlated with those of the blood glucose concentration. (B) The transparent and stretchable integrated platform of temperature and strain sensors shows the simultaneous responses to temperature of human skin during muscle movements or drinking of hot water when the integrated sensor platform was placed on the neck of a male subject. Reproduced with permission from Lee, H.; et al. A graphene-based electrochemical device with thermoresponsive microneedles for diabetes monitoring and therapy; Springer Nature, 2016 [76], and Trung, T.Q.; et al. An all-elastomeric transparent and stretchable temperature sensor for body-attachable wearable electronics; Wiley, 2016 [79].

Figure 5

Examples of smart contact lens for detecting glucose. Schematic diagrams of the measurement setup. Continuous monitoring of the reflected power in response to various glucose concentrations (0–50 mM) versus time measured using the optical powermeter. Reproduced with permission from Elsherif, M.; et al. Wearable contact lens biosensors for continuous glucose monitoring using smartphones; American Chemical Society, 2018 [87].

Figure 6

Schematic of implantable devices. (A) Tattoo-based glucose detection platform. (B) Photograph of an e-tattoo incorporating two electrocardiogram (ECG) electrodes, two hydration sensors and an RTD, all in filamentary serpentine (FS) layout. Synchronously measured ECG under skin indentation. (C) Schematic illustration shows direct hydrogel ink writing. The packing of Pluronic F127-DA micelles in the ink leads to a physically crosslinked hydrogel after printing; photoinitiator allows postphotocrosslinking of the living structures after printing; engineered bacterial cells are programmed to sense the signaling chemicals. 3D printed living tattoo is printed as a tree-like pattern on a thin elastomer layer and adhered to human skin. Reproduced with permission from Bandodkar, A.J.; et al. Tattoo-based noninvasive glucose monitoring: A proof-of-concept study; American Chemical Society, 2015 [98], Liu, X.; et al. 3D printing of living responsive materials and devices; Wiley, 2018 [101] and Wang, Y.; et al. Low-cost, μm-thick, tape-free electronic tattoo sensors with minimized motion and sweat artifacts; Springer Nature, 2018 [106].

Figure 7

Overview of ingestible pill sensor system.