An apparatus including a piezoelectric convertor layer (312); at least one piezoresistive layer (313) on the piezoelectric convertor layer (312); and electrical conductor outputs. The at least one piezoresistive layer (313) includes a plurality of spaced apart piezoresistive electrodes (314). The apparatus is configured such that when the piezoelectric convertor layer (312) is deformed to generate a charge, at least one of the piezoresistive electrodes (314) is stressed, where the at least one piezoresistive layer (313) is configured to control flow of charge from the piezoelectric convertor layer (312). The electrical conductor outputs are electrically connected to the piezoresistive electrodes (314). The outputs are configured to allow the charge from the piezoelectric convertor layer (312) to flow out of the piezoresistive electrodes (314). The electrical conductor outputs are configured relative to the piezoresistive electrodes (314) to allow identification of the at least one piezoresistive electrode (314) which has been stressed based upon the charge on at least one of the electrical conductor outputs.