Browse Prior Art Database

Integrated Force Array Sensor

IP.com Disclosure Number: IPCOM000045958D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Taylor, RH: AUTHOR [+2]

Abstract

A touch sensor with high spatial resolution and capability for force measurement is described. The touch sensor incorporates an acoustic detector having an array of transducers integrated with an underlying silicon layer. An AC voltage is applied between the silicon layer and an upper metallic layer.

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Integrated Force Array Sensor

A touch sensor with high spatial resolution and capability for force measurement is described. The touch sensor incorporates an acoustic detector having an array of transducers integrated with an underlying silicon layer. An AC voltage is applied between the silicon layer and an upper metallic layer.

Swartz and Plummer µ*Ù have described an acoustical detector which has an array of transducers integrated with an underlying silicon integrated circuit array for signal processing. One element of the array is shown in Fig. l. Acoustic signals cause strain in the piezoelectric element. The modulated charge density at the surface of the piezoelectric layer is capacitively coupled to an extended gate electrode which modulates the channel conductance of the associated FET.

We propose the novel application of this structure as a touch sensor with spatial resolution and force measurement ability. One element of the array is shown in Fig. 2.

Features

1. Since steady forces must be measured, we avoid charge amplifiers by making use of the fact that the capacitance of a piezoelectric/ ferroelectric layer varies as a function of applied force. We therefore apply an AC voltage between the substrate and the upper metal layer. The piezoelectric layer has a capacitance Cp. The adhesive capacitance is CA and the gate substrate capacitance is Cs. Cp, Cs, Ca form a potential divider whose ratio varies in sympathy with the force applied to the top surface of the sensor. Charge amplifiers are thus avoided. Also, tuned AC amplifiers may be used for signal conditioning. T...