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Biodegradable stretchable electronics have demonstrated great potential for future applications in stretchable electronics and can be resorbed, dissolved, and disintegrated in the environment. Most biodegradable electronic devices have used flexible biodegradable materials, which have limited conformality in wearable and implantable devices. Here, we report a biodegradable, biocompatible, and stretchable composite microfiber of poly(glycerol sebacate) (PGS) and polyvinyl alcohol (PVA) for transient stretchable device applications. Compositing high-strength PVA with stretchable and biodegradable PGS with poor processability, formability, and mechanical strength overcomes the limits of pure PGS. As an application, the stretchable microfiber-based strain sensor developed by the incorporation of Au nanoparticles (AuNPs) into a composite microfiber showed stable current response under cyclic and dynamic stretching at 30% strain. The sensor also showed the ability to monitor the strain produced by tapping, bending, and stretching of the finger, knee, and esophagus. The biodegradable and stretchable composite materials of PGS with additive PVA have great potential for use in transient and environmentally friendly stretchable electronics with reduced environmental footprint.

In particular, the measurement of metabolites, such as sweat glucose, has been extensively investigated for diabetes management and glucose metabolism monitoring. [7,8] The key requirements to realizing a wearable biosensing system capable of high-accuracy, continuous measurement of glucose include device stability during operation, stretchability for conformal contact to the human body, capability of handling sweat samples accurately and minimization of power consumption.A significant hurdle for wearable electronics is the prolonged operation of the sensor, which necessitates a suitable power source that therein affects the miniaturization, form factor in design and stretchability. For the purpose of monitoring, wearable sensor systems based on the transduction principles of colorimetric, [9][10][11][12][13][14] electrochemical, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] or biofuel cell-based [32][33][34][35][36][37] sensors with deformability are often integrated with a microfluidic device for fluid handling. Specifically, biofuel cell-based metabolite sensors have low energy consumption because they are self-powered. For enzymatic biofuel cell-based biosensors, enzymes have been used in the bioanodes of biofuel cells for the oxidation of metabolites such as glucose [34,35] or lactate. [34,36,37] The use of enzymes in the bioanodes of enzymatic biofuel cells as the catalyst complicates the device fabrication because of the complex immobilization process and enzymes instability by environmental degradation over time. [38,39] The enzymes denature very easily when changes to the surrounding thermal and chemical environment occur, and they lose their reactivity. Moreover, this denaturation is irreversible, and the reactivity is not restored, even if the measurement environment returns to the normal range. To overcome this limitation, a self-powered fuel cell-based sensor system employing catalytic inorganic nanomaterials as electrodes of the fuel cell is of great interest because nanomaterials are less sensitive to environmental changes than enzymes and they have reversible degradation properties. [28,29,38,39] Therefore, the catalytic effect of nanomaterials is expected to be recovered when the detection environment returns to the normal range. Furthermore, nanostructured metal electrodes during glucose sensing provided selectivity toward other interferents such as ascorbic acid and uric acid while lactate is difficult to be oxidized by them. [38,39] Our previous studies Wearable sensor patches for continuous or intermittent monitoring of biomolecules from body fluids are highly desired as a stretchable integrated platform conformable and attachable to the human body. However, realizing such integrated sensor patches is very challenging because of the difficulty of achieving full stretchability, controlling transport of the body fluid, and minimizing power consumption. In this study, a stretchable and self-powered microfluidic-integrated sensor patch comprising a stretchable non-e...

Measurement in liquid media is a major challenge in real-time detection using resonant cantilevers. This is addressed in the present study by fabricating sub-micron thick cantilevers followed by functionalization for biomolecule detection. The fabricated cantilever resonator beams of thickness 165 nm were used for measurements in two systems: (i) human immunoglobulin (HIgG) as the antibody on the cantilever sensing mouse immunoglobulin (MIgG) as corresponding antigen, and (ii) detection of triglyceride (TG) based on the enzymatic hydrolysis with lipase, using tributyrin as a model. In both cases, the beams were functionalized for covalent bonding of the protein receptor. The label-free detection was carried out by measuring the shift in resonance frequency at higher modes, using a laser Doppler vibrometer in liquid and in air. The calibration showed a linear correlation between the bioanalyte concentration and change in the resonance frequency. Notably, detection of antigen mass as low as 434 ± 59fg and triglyceride concentration in the nM range with limit of detection as 7 nM in liquid interface was achieved, greatly improving the sensitivity of bioanalyte detection in liquid samples. Although frequency-based methods are highly sensitive, the issues with measurement liquid medium limit their application. In the present report, these issues were addressed by fabricating sub-micron thick cantilever beam, choosing an appropriate functionalization method without affecting the sensitivity, and measurement at higher modes. These have resulted in circumventing issues like damping and hydrodynamic loading thus improving its potential as real-time sensor.