Electric Field-Driven Self-Assembly of Gold Nanoparticle Monolayers on Silicon Substrates.

Nanoparticles (NPs) bridge the gap between bulk materials and their equivalent molecular/atomic counterparts. The physical, optical, and electronic properties of individual NPs alter with the changes in their surrounding environment at the nanoscale. Similarly, the characteristics of thin films of NPs depend on their lateral and volumetric densities. Thus, attaining single monolayers of these NPs would play a vital role in the improved characteristics of semiconductor devices such as nanosensors, field effect transistors, and energy harvesting devices. Developing nanosensors, for instance, requires precise methods to fabricate a monolayer of NPs on selected substrates for sensing and other applications. Herein, we developed a physical fabrication method to form a monolayer of NPs on a planar silicon surface by creating an electric field of intensity 5.71 × 104 V/m between parallel plates of a capacitor, by applying a DC voltage. The physics of monolayer formation caused by an externally applied electric field on the gold NPs (Au-NPs) of size 20 nm in diameter and possesses a zeta potential of -250 to -290 mV, is further analyzed with the help of the finite element simulation. The enhanced electric field, in the order of 108 V/m, around the Au-NPs indicates a high surface charge density on the NPs, which results in a high electric force per unit area that guides them to settle uniformly on the surface of the silicon substrate.

Human Vital Signs Detection Methods and Potential Using Radars: A Review.

Continuous monitoring of vital signs, such as respiration and heartbeat, plays a crucial role in early detection and even prediction of conditions that may affect the wellbeing of the patient. Sensing vital signs can be categorized into: contact-based techniques and contactless based techniques. Conventional clinical methods of detecting these vital signs require the use of contact sensors, which may not be practical for long duration monitoring and less convenient for repeatable measurements. On the other hand, wireless vital signs detection using radars has the distinct advantage of not requiring the attachment of electrodes to the subject's body and hence not constraining the movement of the person and eliminating the possibility of skin irritation. In addition, it removes the need for wires and limitation of access to patients, especially for children and the elderly. This paper presents a thorough review on the traditional methods of monitoring cardio-pulmonary rates as well as the potential of replacing these systems with radar-based techniques. The paper also highlights the challenges that radar-based vital signs monitoring methods need to overcome to gain acceptance in the healthcare field. A proof-of-concept of a radar-based vital sign detection system is presented together with promising measurement results.

MOMSense: Metal-Oxide-Metal Elementary Glucose Sensor.

In this paper, we present a novel Pt/CuO/Pt metal-oxide-metal (MOM) glucose sensor. The devices are fabricated using a simple, low-cost standard photolithography process. The unique planar structure of the device provides a large electrochemically active surface area, which acts as a nonenzymatic reservoir for glucose oxidation. The sensor has a linear sensing range between 2.2 mM and 10 mM of glucose concentration, which covers the blood glucose levels for an adult human. The distinguishing property of this sensor is its ability to measure glucose at neutral pH conditions (i.e. pH = 7). Furthermore, the dilution step commonly needed for CuO-based nonenzymatic electrochemical sensors to achieve an alkaline medium, which is essential to perform redox reactions in the absence of glucose oxidase, is eliminated, resulting in a lower-cost and more compact device.