A highly sensitive thermometer system for a living cell is proposed, fabricated, and evaluated. The system possesses a resonant thermal sensor surrounded by vacuum in a microfluidic chip. The measurement principle relies on resonant frequency tracking of the resonator in temperature variations due to the heat from a sample cell; the heat is conducted from the sample cell in the microfluidic channel via a heat guide connecting the resonator to a sample stage. This configuration can reduce heat loss from the resonator to the surroundings and damping in water. Two types of resonators are prepared, i.e., a cantilevered resonator and a double-supported resonator. The resonator sizes as a sensor are 30 × 50 × 1.5 μm in the cantilevered resonator, 30 × 75 × 0.40 μm in the double-supported one, respectively. The temperature and thermal resolutions of 79 μK and 1.90 nW, respectively, are achieved using the double-supported resonator. Two types of heat emissions from single brown fat cells are detected; one is continuous heat generation in the presence of chemical stimulation by a norepinephrine solution, and the other is pulsed without any stimulation.

In this paper, a centimeter-scale monolayer molybdenum disulfide (MoS ₂ ) film deposition method has been developed through a simple low-pressure chemical vapor deposition (LPCVD) growth system. The growth pressure dependence on film quality is investigated in this LPCVD system. The layer nature, electrical characteristic of the as-grown MoS ₂ films indicate that high quality films have been achieved. In addition, a hydrofluoric acid treated SiO ₂ /Si substrate is used to improve the quality of the MoS ₂ films. Piezoresistive strain sensor based on the monolayer MoS ₂ film elements is fabricated by directly patterning metal contact pads on MoS ₂ films through a silicon stencil mask. A gauge factor of 104 ± 26 under compressive strain is obtained by using a four-point bending method, which may inspire new possibilities for two-dimensional (2D) material-based microsystems and electronics.

The microfabrication with a magnetostrictive Tb_xDy_(1−x)Fe_y thin film for magnetic microactuators is developed, and the magnetic and magnetostrictive actuation performances of the deposited thin film are evaluated. The magnetostrictive thin film of Tb_xDy_(1−x)Fe_y is deposited on a metal seed layer by electrodeposition using a potentiostat in an aqueous solution. Bi-material cantilever structures with the Tb_0.36Dy_0.64Fe_1.9 thin-film are fabricated using microfabrication, and the magnetic actuation performances are evaluated under the application of a magnetic field. The actuators show large magnetostriction coefficients of approximately 1250 ppm at a magnetic field of 11000 Oe.

This paper reports on the fabrication and evaluation of a novel liquid thermocouple. The sensor is composed of two microfluidic reservoirs, a heat stage, and three electrodes. One reservoir contains a polymer electrolyte-polyethylene glycol-NaOH (PEG-NaOH)-and the other an iodine aqueous solution. The ionic liquids are electrically connected via a bridging electrode deposited over the heat stage. Varying the temperature of the heat stage causes a temperature distribution across the liquids, which changes the total thermoelectric voltage across the two ionic liquids. The device is fabricated using conventional microfabrication techniques and the thermoelectric power response and sensitivity are evaluated. The output voltage of the thermocouple increases linearly with the input temperature. The liquid thermocouple has a Seebeck coefficient of 10.6 mV/K and an estimated temperature resolution of 8.94 mK. The ease of fabrication and the characterization results of this ionic liquid-based thermocouple show that it has the potential for integration in microfluidics-based applications such as biosensing and lab-on-a-chip.

This review presents several sensors with dimensions at the nano- and micro-scale used for biological applications. Two types of cantilever beams employed as highly sensitive temperature sensors with biological applications will be presented. One type of cantilever beam is fabricated from composite materials and is operated in the deflection mode. In order to achieve the high sensitivity required for detection of heat generated by a single mammalian cell, the cantilever beam temperature sensor presented in this review was microprocessed with a length at the microscale and a thickness in the nanoscale dimension. The second type of cantilever beam presented in this review was operated in the resonant frequency regime. The working principle of the vibrating cantilever beam temperature sensor is based on shifts in resonant frequency in response to temperature variations generated by mammalian cells. Besides the cantilever beam biosensors, two biosensors based on the electric cell-substrate impedance sensing (ECIS) used to monitor mammalian cells attachment and viability will be presented in this review. These ECIS sensors have dimensions at the microscale, with the gold films used for electrodes having thickness at the nanoscale. These micro/nano biosensors and their mammalian cell applications presented in the review demonstrates the diversity of the biosensor technology and applications.