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Herein, we successfully developed a thread-based analytical device (μTAD) for simultaneous immunosensing of two biomolecules with attomolar sensitivity by using a photothermal effect. A photothermal effect exploits a strong light-to-heat energy conversion of plasmonic metallic nanoparticles at localized surface plasmon resonance. The key innovation is to utilize the cotton thread to realize this sensor and the use of chitosan modification for enhancing the microfluidic properties, for improving the efficiency of photothermal conversion, and for sensor stability. The developed μTAD sensor consists of (i) a sample zone, (ii) a conjugation zone coated with gold nanoparticles bound with an antibody (AuNPs-Ab2), and (iii) a test zone immobilized with a capture antibody (anti-Ab1). The prepared μTAD is assembled in a custom three-dimensional (3D) printed device which holds the laser for illumination and the thermometer for readout. The 3D-printed supportive device enhances signal response by focusing light and localizing the heat generated. For proof of concept, simultaneous sensing of two key stress and inflammation biomarkers, namely, cortisol and interleukin-6 (IL-6), are monitored using this technique. Under optimization, this device exhibited a detection linear range of 2.0–14.0 ag/mL (R2= 0.9988) and 30.0–360.0 fg/mL (R2= 0.9942) with a detection limit (LOD) of 1.40 ag/mL (∼3.86 amol/L) and 20.0 fg/mL (∼950.0 amol/L) for cortisol and IL-6, respectively. Furthermore, the analysis of both biomolecules in human samples indicated recoveries in the range of 98.8%–102.88% with the highest relative standard deviation being 3.49%, offering great accuracy and precision. These results are the highest reported sensitivity for these analytes using an immunoassay method. Our PT-μTAD strategy is therefore a promising approach for detecting biomolecules in resource-limited point-of-care settings.

There is a need to develop cost-effective and compact solutions for Smart Home monitoring. Existing monitoring systems depend on continuous power sources to support the operation of sensors and electronics modules used therein. In this article, we present three simple battery-free, Radio-Frequency Identification (RFID)-based solutions for real-time monitoring of the orientation of an object using a tilt sensor based on a metallic bead, an entry detection system utilizing a reed switch-based proximity sensor, and a temperature crossing event detection using a thermistor. All sensors are integrated with individual passive RFID tags. The proposed sensing mechanisms were also combined to achieve multi-modal logic sensing operation. Active events (change in position, motion, and temperature) would alter the state of the corresponding flexible RFID sensors to transmit warning signals wirelessly to an RFID reader, realizing a simple RFID-based Smart Home network. The proposed platform has been validated through extensive simulation and actual measurements.