Active Thermal Sensor for Improved Distributed Temperature Sensing in Haptic Arrays

D Cheneler,M C L Ward

doi:10.1155/2018/9631236

Abstract

The efficacy of integrating temperature sensors into compliant pressure sensing technologies, such as haptic sensing arrays, is limited by thermal losses into the substrate. A solution is proposed here whereby an active heat sink is incorporated into the sensor to mitigate these losses, while still permitting the use of common VLSI manufacturing methods and materials to be used in sensor fabrication. This active sink is capable of responding to unknown fluctuations in external temperature, that is, the temperature that is to be measured, and directly compensates in real time for the thermal power loss into the substrate by supplying an equivalent amount of power back into the thermal sensor. In this paper, the thermoelectric effects of the active heat sink/thermal sensor system are described and used to reduce the complexity of the system to a simple one-dimensional numerical model. This model is incorporated into a feedback system used to control the active heat sink and monitor the sensor output. A fabrication strategy is also described to show how such a technology can be incorporated into a common bonded silicon-on-insulator- (BSOI-) based capacitive pressure sensor array such as that used in some haptic sensing systems.

Highlights

There are many variants of silicon-based sensors available today [1,2,3]
For the purposes of simulation, it will be assumed that the temperature sensor will be made out of a gold layer 200 nm thick and with the same width and length as the active sink
It should be noted that gold was considered as it is compatible with a number of MEMS fabrication facilities

Summary

Introduction

There are many variants of silicon-based sensors available today [1,2,3]. Many of the compliant sensors, in particular strain and pressure sensors, require temperature compensation in order to mitigate thermal expansion effects [2]. Many designs incorporate some manner of structure to prevent/correct for thermal expansion [4] or some manner of temperature sensor, usually a temperature-sensitive resistor, to facilitate correction of the sensor output [5, 6]. These integrated temperature sensors do not provide a measure of the actual ambient temperature, but rather the temperature of the compliant sensor, which is a function of the ambient temperature and of thermal losses through the substrate. Temperature sensors are often incorporated into these arrays to provide a more biomimetic sensing modality [10, 11]

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