Microheater: material, design, fabrication, temperature control, and applications-a role in COVID-19

Abstract

Heating plays a vital role in science, engineering, mining, and space, where heating can be achieved via electrical, induction, infrared, or microwave radiation. For fast switching and continuous applications, hotplate or Peltier elements can be employed. However, due to bulkiness, they are ineffective for portable applications or operation at remote locations. Miniaturization of heaters reduces power consumption and bulkiness, enhances the thermal response, and integrates with several sensors or microfluidic chips. The microheater has a thickness of ~ 100 nm to ~ 100 μm and offers a temperature range up to 1900℃ with precise control. In recent years, due to the escalating demand for flexible electronics, thin-film microheaters have emerged as an imperative research area. This review provides an overview of recent advancements in microheater as well as analyses different microheater designs, materials, fabrication, and temperature control. In addition, the applications of microheaters in gas sensing, biological, and electrical and mechanical sectors are emphasized. Moreover, the maximum temperature, voltage, power consumption, response time, and heating rate of each microheater are tabulated. Finally, we addressed the specific key considerations for designing and fabricating a microheater as well as the importance of microheater integration in COVID-19 diagnostic kits. This review thereby provides general guidelines to researchers to integrate microheater in micro-electromechanical systems (MEMS), which may pave the way for developing rapid and large-scale SARS-CoV-2 diagnostic kits in resource-constrained clinical or home-based environments.

Keywords: Gas sensor; Heater; Micro hot plate; Microheater; Temperature control; Thin-film heater.

Fig. 1

Internal heating systems. (a) Microfluidic device incorporated with co-running heating channels (grey) and working sample (black) (de Mello et al. 2004), (b) Endothermic/exothermic heater (Guijt et al. 2003) Reprinted with permission from RSC

Fig. 2

External heating systems. (i) Contact heater (Yu et al. 2014) Reprinted with permission from RSC (ii) Non-contact heaters. (a) Schematic drawing of induction heating based on the magnetic nanoparticle-embedded PDMS (MNP-PDMS) chip (Kim et al. 2010) Reprinted with permission from IOP, (b) PDMS chip bonded on LiNbO₃ piezoelectric substrate (Ha et al. 2015) Reprinted with permission from Nature

Fig. 3

Ideal characteristics of a good microheater

Fig. 4

Different microheater utilized by researchers (a) Ti/Ag microheater heating up to failure (Guan and Puers 2010) Reprinted with permission from Elsevier, (b) Cr–CrN, and CrN–Pt based microheater (Chang and Hsihe 2016) Reprinted with permission from Elsevier, (c) Optical micrograph of CNT growth structures in AMS 350 nm process (Roy et al. 2019) Reprinted with permission from MDPI, (d) Change in sheet resistance of AZO/Ag-SnOx/AZO thin film as a function of bending cycles (Wang et al. 2020b) Reprinted with permission from Elsevier, (e) liquid metal-based microheaters (Jinsol and Jungchul 2014) Reprinted with permission from IEE, (f) Liquid microheater with parallel ventilating side-channels to trap the air (Zhang et al. 2020) Reprinted with permission from MDPI

Fig. 5

Classification of the various substrate for microheater so far investigated by various researchers

Fig. 6

Different substrates employed in microheater (Jinsol and Jungchul ; Lin et al. ; Petrucci et al. ; Resnik et al. ; Son et al. ; Weir et al. ; Yeom et al. ; Yin et al. ; Yu et al. 2017) Reprinted with permission from IEEE, MDPI, Elsevier, AIP, Springer Nature, Wiley, and IOP

Fig. 7

Passive layer deposited microheaters to improve stability. (a) Silver nanowires in colourless polyimide (cPI) and PMMA (Shi et al. 2018), (b) SiO₂ deposition on Pt microheater to protect the device from the environment (Bai et al. 2019) Pictures retrieved from Springer Nature, (c) SiO₂ passivation layer was deposited to prevent oxidation of poly-Si (Hwang et al. 2011b) Reprinted with permission from MDPI

Fig. 8

Illustrative diagram of different microheater designs so far investigated by various researchers (Botau et al. ; Das and Kakoty ; Ha et al. ; Han and Meyyappan ; Hasan et al. ; Holt et al. ; Horade et al. ; Hwang et al. ; Jinsol and Jungchul ; Kim et al. ; Lee et al. ; Nieto et al. ; Petrucci et al. ; Rajput et al. ; Roy et al. ; Ruiqi et al. ; Wu et al. ; Yu et al. ; Zhong et al. 2009). (a) Inverted C shaped, (b) Rectangular mesh pattern, (c) Lines, (d) Plate, (e) Double spiral Square, (f) Curved double spiral square, (g) Ring-shaped, (h) Square grilled, (i) Double spiral, (j) Octogen, (k) Circular, (l) Dual C, (m) Inverted U, (n) Meander, (o) Meander with rounded corners, (p) Dual meander, (q) U Dual meander, (r) Wing, (s) Hook

Fig. 9

(a) 2D 4 × 4 microheater array with an enlarged view of heater (Jung et al. 2011) Retrieved with permission from Elsevier, (b) 3D microheater array with lead lines are grade crossings with overpasses (Horade et al. 2016) Retrieved with permission from CCSE

Fig. 10

Microheater fabrication techniques

Fig. 11

Illustrations of the microheater fabrication process. (a) Schematic of PVD, (b) PECVD (Pessoa et al. 2015) Reprinted with permission from Elsevier, (c) Injection molding fabrication processes of liquid metal microheaters (Jinsol and Jungchul 2014) Reprinted with permission from IEEE, (d) Schematic of an electrochemical cell for the direct electrodeposition (Augello and Liu 2015) Reprinted with permission from Elsevier, (e) Illustrative of homemade spray pyrolysis system (Gharesi and Ansari 2016) Reprinted with permission from IOP, (f) Illustration of micro-pen direct writing and laser sintering fabrication procedure (Cai et al. 2011) Reprinted with permission from Elsevier

Fig. 12

Process involved in the automatic temperature control module

Fig. 13

Temperature sensors adapted in microheater temperature measurement (Li et al. ; Scorzoni et al. 2014) Retrieved with permission from Springer Nature and IEEE

Fig. 14

Setup to determine TCR of the nano-silver ink microheater (du Plessis et al. 2017) Retrieved with permission from SPIE

Fig. 15

(i) Switching temperature control. a Block diagram of ATMega 8535 temperature control system (Megayanti et al. 2016), b PDMS microfluidic chip with an integrated microheater, thermal sensor, and temperature control (Wu et al. 2009) Pictures retrieved with permission from AIP, c Illustration of the temperature control system and electric connections with microheater (Nie et al. 2014) Retrieved with permission from Springer Nature. (ii) Block diagram of PI closed-loop feedback control (Phatthanakun et al. 2012) Retrieved with permission from IEEE. (iii) PID temperature control. a Block diagram of PID temperature controller in Lab-VIEW software (Zainal Alam et al. 2014), b Illustration of a real-time temperature monitoring system based on MCU control (Han et al. 2013), c Schematic diagram of MCU (STM32F103RCT6) temperature control system (Cui et al. 2016) Pictures retrieved with permission from Springer Nature, d PCR Chip temperature Control System (Hwang et al. 2015) Retrieved with permission from SERSC, e Block diagram of the microheater control unit (Holt et al. 2017) Retrieved with permission from Springer Nature

Fig. 16

Potential applications of the microheater

Fig. 17

Microheaters used in gas sensing. (a) optical image of the gas sensor with microheater and sensing electrode (Hwang et al. 2011a), (b) Micrographs of micro-hotplate on a glass substrate (Chang and Hsihe 2016), (c) Fabricated H₂ sensor (Yoon et al. 2012) Pictures retrieved with permission from Elsevier, (d) SEM image of the fabricated 3-D microheater (Xu et al. 2011) Retrieved with permission from IEEE, (e) Photograph of four SiC microheaters (Harley-Trochimczyk et al. 2017) Retrieved with permission from IOP, (f) NO gas sensor with integrated 3C-SiC microheater (Jae-Cheol and Gwiy-Sang 2010) Retrieved with permission from IEEE, (g) 3 × 3 microheater array device with three-layer structure (Bai et al. 2019) Retrieved with permission from Springer Nature, (h) Surface micromachined NO2 gas sensor with integrated microheater (S. E. Moon et al. 2012) Retrieved with permission from Ingenta, (i) Schematic setup for testing Ti-stripe microheater (Kaushal and Das 2016) Retrieved with permission from OSA, (j) Fabricated MEMS-based porous SnO2 film chip (Dai et al. 2013) Retrieved with permission from Springer Nature

Fig. 18

Microheaters utilized in the biological sector. (a) Microheater with trench geometry on the glass substrate (Scorzoni et al. 2015) Reprinted with permission from Elsevier, (b) Copper microheater for dynamic microbioreactor (Utomo et al. 2019) Reprinted with permission from AIP, (c) A low cost microheater for aerosol generation (Liu et al. 2014) Reprinted with permission from Elsevier, (d) Tagging module in capsule endoscope (Ruiqi et al. 2011) Reprinted with permission from IEEE, (e) Si nanowire-heater device (Son et al. 2017) Reprinted with permission from Springer Nature

Fig. 19

Microheaters used in cell culturing and incubation. (a) Cell culturing temperature Controlled chip (Yamanishi et al. 2008) Reprinted with permission from IEEE, (b) Battery-powered incubation system with an enlarged view of two heater designs (Byers et al. 2019) Reprinted with permission from RSC

Fig. 20

Microheaters for DNA amplification. (a) Fabricated thin film heater/RTD PCR chip (Jeong et al. 2018), (b) Microheater and temperature sensor patterned glass slide (Hilton et al. 2012) Pictures reprinted with permission from Springer Nature, (c) External electrical circuit employed to drive the Ti microheater device (Javed et al. 2012) Reprinted with permission from AIP, (d) Photograph of a fabricated Cu heater in Cu-clad PI substrate (Moschou et al. 2014) Reprinted with permission from Elsevier, (e) PCR chip with reusable electrode part (Cao et al. 2015) Reprinted with permission from Trans Tech, (f) Optimized meander electrode with holes (Cui et al. 2016) Reprinted with permission from Springer Nature, (g) Illustration of induction heating based on the magnetic nanoparticle-embedded PDMS (MNP-PDMS) chip (Kim et al. 2010) Reprinted with permission from APS, (h) Image of thin-film Au resistors (Nie et al. 2014) Reprinted with permission from Springer Nature, (i) Flexible PI film with integrated heater and a temperature sensor (Lee et al. 2008) Reprinted with permission from IEEE

Fig. 21

Microheaters implemented in biochemical research. (a) SEM image of the Ag/Ti microheater (Guan and Puers 2010) Reprinted with permission from Elsevier, (b) Octogen gold heater on polyimide thin film substrate (Yu et al. 2015) Reprinted with permission from ASME, (c) Au/Cr microheater on the glass substrate for cross-contamination free parallel elution of specifically bound aptamers (Lee et al. 2013) Reprinted with permission from Springer Nature, (d) 4-by-4 matrix microheater array device (Horade et al. 2016) Reprinted with permission from CCSE

Fig. 22

(a) EGaIn liquid metal-based microheater (Zhang et al. 2020) Reprinted with permission from MDPI, (b) Temperature-controllable microheater chip for colour display devices (Kim et al. 2015), (c) Bluetooth-integrated temperature-controlled wearable heater (Jang et al. 2017) Pictures reprinted with permission from Springer Nature

Fig. 23

(a) Microheater array for powder sintering (Holt et al. 2018) Reprinted with permission from Elsevier, (b) Curved CNT-film microheater array on PET for thermochromic displays (Liu et al. 2011) Reprinted with permission from Wiley, (c) Bending performance of actuators with different heater patterns at similar temperature (Cao and Dong 2019) Reprinted with permission from Elsevier, (d) Illustration of a Tungsten microheater designer anvil showing the eight diamond encased electrodes (Weir et al. 2009) Reprinted with permission from AIP, (e) Optic images of combustion flame in the nano initiator (Kaili et al. 2008) Reprinted with permission from IEEE, (f) Microheater integrated fluid channels for testing micro-solid oxide fuel cell components (Jiang et al. 2012) Reprinted with permission from Elsevier, (g) Al/Ti microheater in the micro thruster (Li et al. 2017) Reprinted with permission from Springer Nature, (h) Printed Joule heating device with electrodes section, printed zinc salt film, and microheater (Tran et al. 2020) Reprinted with permission from MDPI